Canola protein

Trends in Food Science & Technology 22 (2011) 21e39

Review

Canola proteins:
composition, the chemical composition (amino acids and protein fractions),
production and isolation techniques, functional properties, al-
lergenicity, food applications and potential uses of canola pro-
extraction, functional teins for the production of bioactive compounds are
highlighted.

properties,
Introduction
bioactivity, Canola/Rapeseed is an important oilseed crop in many
countries and is considered to be the second most abundant
source of edible oil in the world. Canola is the rapeseed va-
applications as a food riety which was developed in Canada. According to the
United States Department of Agriculture, canola production

ingredient and exceeds 40 million metric tons per year (USDA, 2004).
Canada is a world leader in the large-scale production of
high quality canola varieties, which are characterized by
allergenicity e A low erucic acid (<2%) and glucosinolate (<30 lmol/g) con-
tents (Ghodsvali, Khodaparast, Vosoughi, & Diosady,
2005).
practical and critical Canola seeds contain approximately 40% oil and
17e26% protein (Uppstrom, 1995). Canola meal, which

review is a by-product of canola oil extraction, is a highly rich
raw material and contains up to 50% protein on a dry basis.
The major protein constituents of canola meal are napin
Mohammed Aidera,* and and cruciferin, which are storage proteins, and oleosin,
which is a structural protein associated with the oil fraction
Chockry Barbanab (Uppstrom, 1995). This particularity makes canola protein
a potential ingredient for use in the food industry. Many
a
Department of Food Engineering, Universit Laval,
e characteristics of canola protein are favorable for human
Qubec, Qc, G1K 7P4, Canada
e nutrition. The amino acid composition of canola meal is
(Tel.: D1 418 656 2131x4051; well balanced and can be used for human nutrition
e-mail: mohammed.aider@fsaa.ulaval.ca) (Ohlson Anjou, 1979; Mariscal-Landin, Reis de Souza,
b
Tecnolog y Bioqu
ıa ımica de los Alimentos, Facultad Parra, Aguilera, Mar, 2008). In addition, the protein ef-
Veterinaria, Universidad de Zaragoza, C/ Miguel ﬁciency ratio of canola meal is 2.64, which is higher than
Servet 177, 50013 Zaragoza, Spain that of soybean (2.19) (Delisle et al., 1984). Canola
proteins have shown interesting and promising functional
properties and could be potentially used in various food
There is a well-recognized connection between the use of matrices (Khattab Arntﬁeld, 2009; Xu Diosady,
plant proteins in functional foods, nutraceuticals and other 1994a, 1994b). Some properties of canola proteins were
natural health products and health promotion and disease comparable to those of casein and better than those of other
risk reduction. Plant proteins are largely used in the food in- plant proteins, such as soybean, pea, and wheat (Ghodsvali
dustry, and canola/rapeseed proteins are regarded as potential et al., 2005). However, the usefulness of canola protein ex-
ingredients that may be used as food additives. In this review, tracts is limited by the presence of some undesirable com-
pounds, such as glucosinolates, phytates, and phenols,
which are responsible for the toxic, antinutritional and
* Corresponding author. undesirable coloration capacity of canola proteins. Also,
0924-2244/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tifs.2010.11.002

22 M. Aider, C. Barbana / Trends in Food Science Technology 22 (2011) 21e39

canola meal contains approximately 20% (w/w) carbohy- significantly affected the final protein composition
drates, including soluble sugars (Lacki Duvnjak, 1998). (Chabanon, Chevalot, Framboisier, Chenu, Marc, 2007).
However, after protein extraction, the major part of these The amino acid composition of canola meals was ana-
saccharides is eliminated. Efforts are focusing to develop lyzed by Shahidi, Naczk, Hall, and Synowiecki (1992).
canola protein products for food applications. Recently, The authors reported that the canola meals used had
Burcon NutraScience Corporation has announced that the a high content of glutamic acid (16.77e18.63% w/w pro-
Division of Biotechnology and GRAS Notice Review of tein). However, they found that tyrosine, methionine and
the Center for Food Safety and Applied Nutrition of the cysteine were present in lower concentrations. In thestudy
FDA has formally acknowledged receipt of Burcon’s of Shahidi et al. (1992), a two-phase solvent extraction pro-
GRAS notification for its canola protein ingredients. cess was used, and it was shown that this process did not
The present review summarizes the chemical and struc- significantly alter the amino acid composition of canola/
tural compositions of canola proteins, the processes used rapeseed meals. However, a decrease in the proline content
for canola protein extraction, the functional properties was observed. Of the essential amino acids, cysteine, me-
and examples of canola protein applications in different thionine, isoleucine and leucine were also present at low
food matrices. The potential of use of canola proteins for concentrations. The two-phase solvent extraction process
the production of bioactive peptides is also highlighted. slightly increased the cysteine content in meals obtained
from some canola varieties. The authors stated that a slight
Chemical and structural compositions reduction in the concentration of lysine might be due to the
Amino acid profile formation of lysinoalanine in the alkaline solutions used for
The amino acid compositions of the canola protein iso- protein extraction. The calculated protein efficiency ratios
lates have been studied and reported by several researchers; (PER) of rapeseed meals based on the leucine and proline
these proteins are well balanced and show high glutamine, contents or on the leucine and tyrosine contents were
glutamic acid, arginine and leucine contents and low 2.19e2.64 (Shahidi et al., 1992).
amounts of sulfur-containing amino acids, which are prob- Klockeman, Toledo, and Sims (1997) studied the amino
ably altered during the industrial oil extraction process acid profile of untreated canola meal and found that it was
(Table 1). Indeed, the amino acid composition depends on similar to the published values for high erucic acid rapeseed
the process used for protein extraction from the canola protein extract (Shahidi, 1990) but had lower values for cys-
meal residue. Usually, up to 30% of the total protein ini- teine and valine. The canola protein isolate (CMPI)
tially present in rapeseed meal is extracted in an alkaline reported in the work of Shahidi (1990) contained signifi-
medium, and large-scale purification of canola proteins cantly more leucine, phenylalanine, arginine, and asparagine
and less isoleucine than a high erucic acid canola reference
protein. When compared to defatted canola meal, CMPI con-
Table 1. Amino acid composition expressed as mass percent of the
tains more isoleucine and arginine and less lysine. The ob-
globulins isolate and the albumins isolate: from (Chabanon et al., served differences between the CMPI reported by
2007) Klockeman et al. (1997) and published values for canola
(rapeseed) proteins may indicate that the genetic manipula-
Amino acid Albumin isolate Globulin isolate
tions involved in the development of canola varieties of rape-
Asx 5.1 9.5
seed have resulted in changes in seed storage proteins, which
Glx 30.4 20.2
Ser 4.1 4.4 are low in both erucic acid and glucosinolate contents. Fur-
His 4.7 5.1 thermore, lysine was the only essential amino acid in
Gly 1.9 1.7 CMPI and was present in significantly lower amounts com-
Thr 4.4 4.7 pared with the crude commercial hexane defatted canola
Ala 3.4 3.5
meal. Although there was a decrease in the measured lysine,
Arg 8.6 9.8
Tyr 3.7 4.5 no significant change in the serine or cysteine contents was
Cys 0.1 0.0 observed (Klockeman et al., 1997). It is important to note
Val 4.3 3.3 that in the work of Klockeman et al. (1997), no lysinoalanine
Met 0.5 (0.6)a 1.2 (1.2)a was detected in the studied canola meal protein isolate
Phe 3.7 (7.4)b 5.7 (10.2)b
(CMPI), which follows previous reports of lysinoalanine
Ile 4.3 5.3
Leu 8.5 9.1 levels of 100 ppm in commercial hexane-extracted seeds
Lys 6.2 4.7 (Deng, Barefoot, Diosady, Rubin, Tzeng, 1990). The
Pro 6.4 6.8 levels of isoleucine, lysine, and aspartic acid present in the
Trp n.d. n.d. CMPI were lower than those in soybean protein isolates
*Asx: aspartic acid þ asparagine; Glx: glutamic acid þ glutamine. (Nehez, 1985). Protein quality was evaluated using the calcu-
n.d.: Not determined. lated protein digestibility corrected amino acid score
a
Met þ Cys. (PDCAAS) values. It is well recognized that (PDCAAS)
b
Phe þ Tyr.
scores 1.00 indicate an amino acid deficiency, while scores

M. Aider, C. Barbana / Trends in Food Science Technology 22 (2011) 21e39 23

!1.00 are considered to be equivalent when proteins are 2005). Oleosins are low-molecular-weight (15e26 kDa)
compared. All (PDCAAS) scores for the present CMPI based alkaline proteins and represent about 2e8% of the total
on the reference values for average infants were 1.00, with canola seed proteins (Huang, 1992). Canola meal also con-
the lowest scores for methionine and cysteine. The essential tains minor proteins, such as thionins, trypsin inhibitors and
amino acid with the lowest (PDCAAS) score based on the re- lipid transfer proteins (LTP) (Berot, Compoint, Larr, e
quirements for 2À5-year-olds was lysine. For comparison, Malabat, Guguen, 2005). These different protein frac-
e
the lowest score found for soybean protein for this age group tions can be easily separated by chromatography, mem-
was methionine plus cysteine (Henley Kuster, 1994). All brane filtration, such as ultrafiltration, and electrophoretic
(PDCAAS) scores calculated for 10À12-year-olds and techniques. In canola seeds, the albumin and globulin frac-
adults were 1.00. The (PDCAAS) analysis indicates that tions represent the majority of proteins. The molecular
CMPI has a lower protein quality than soy protein for average weight of the albumin fraction is lower than the globulins.
infants and 2À5-year-olds. If CMPI is used in products for The relative proportions of these fractions in canola
infants, blending the CMPI with other proteins will be proteins are variable and depend on many factors, such as
necessary to balance the amino acid profile. The limiting the climate environment during maturation and the pres-
amino acids in soy protein and CMPI are complementary ence of sulfur compounds. The amount of albumin depends
for 2À5-year-olds; the two could be blended for nutritional on the contribution of sulfur compounds, which is depen-
supplements for this age group. Because all (PDCAAS) dent on the cysteine and methionine metabolism of the
scores for the canola protein isolate were !1.00 for both plant. At the same time, the amount of globulins in
10À12-year-olds and adults, this protein extract represents the overall protein composition of canola depends on the
an excellent source of dietary proteins for products formu- amount of non-nitrogenous compounds. The amount of
lated for both of these age groups. CMPI and soy protein each protein fraction in the canola meal depends on the
have equivalent nutritional qualities for these two age extraction and purification process (Yew-Min, Levente,
groups. Compared to egg albumin, the canola albumin frac- Leon, 1988). Generally, the estimated quantities of globulin
tion contains more histidine, cysteine, methionine, lysine and and albumin are 60% and 40%, respectively (Mieth et al.,
arginine; however, it contains less phenylalanine, tyrosine 1983).
and isoleucine (Mieth, Schwenke, Raab, Bruckner, 1983). Chung, Lei, and Li-Chan (2005) conducted a study in
which proteins were extracted from dehulled and defatted
Canola protein fractions flaxseed/canola (NorMan cultivar) and fractionated by
The canola proteins of interest are mainly storage pro- anion exchange chromatography to yield a fraction with
teins located in the embryo because they are abundant. a molecular weight of 365 kDa, as determined by Sephacryl
They represent approximately 80% of the total protein S-300 gel permeation chromatography. According to their
(Hoglund, Rodin, Larsson, Rask, 1992; Mieth et al., results, the authors stated that reducing and non-reducing
1983). Canola proteins can be classified to four groups: al- SDS-PAGE revealed three predominant bands of 20, 23
bumins, which constitute the water soluble fraction; globu- and 31 kDa, respectively, and two predominant bands at
lins, which are soluble in salt solutions; prolamins, which is 40 and 48 kDa, respectively. In this study, the isoelectric
the ethanol soluble fraction; and glutelins, which is the focusing technique was used to separate three components
fraction that is insoluble in all of the solvents mentioned with isoelectric points (pI ) of 4.7, 5.1, and 5.6, and acidic
above. Canola proteins can be also divided into various (pI 4.5, 5.9, 6.1) and basic (pI 9.6) components were
fractions according to the corresponding sedimentation co- observed under reducing and denaturing conditions. The
efficient in Svedberg units (S). This coefficient indicates the major fraction of canola had high disulfide but low sulfhy-
speed of sedimentation of a macromolecule in a centrifugal dryl content, high contents of glutamate (or glutamine) and
field. For canola proteins, the following fractions have been aspartate (or asparagine), and a low lysine/arginine ratio.
reported: 12 S, 7 S and a split 2 S, 1.7 S or 1.8 S. Cruciferin According to these properties, the cultivar used in this study
and napin are the two major families of storage proteins showed a lower content of the above-mentioned compounds
found in canola/rapeseed. Napin is a 2 S albumin, and cru- than typical canola globulins. Fourier transform Raman
ciferin is a 12 S globulin. They constitute 20% and 60% of spectroscopy (FT-Raman spectroscopy) also indicated
the total protein content of mature seeds, respectively a high b-sheet content and a strong band near 1065 cmÀ1
(Hoglund et al., 1992). Napins are low molecular weight that is typical of inter-molecular sheet interactions, which
proteins (12.5e14.5 kDa) characterized by strong alkalinity supports the oligomeric nature of the protein.
that is mainly due to a high level of amidation of amino Canola is well recognized as an economically important
acids. Napin possesses good foaming properties (Schmidt farm-gate crop in many countries, such as Canada and the
et al., 2004). Cruciferin is a neutral protein with a high mo- USA; to further explore the potential of canola proteins as
lecular weight (300e310 kDa) and several subunits. In its a value-added food ingredient, a better understanding of the
native form, cruciferin acts as a gelling agent. Oleosin, fundamental properties of the two major canola proteins is
the other major type of protein found in canola, is a struc- necessary (Wu Muir, 2008). A study was reported in
tural protein associated with oil bodies (Ghodsvali et al., which two major protein components, cruciferin and napin,


were isolated from defatted canola meal by Sephacryl supernatant-derived canola protein isolate, the predominant
S-300 gel filtration chromatography. SDS-PAGE showed species was the 2 S protein. These differences lead to dif-
that cruciferin consists of more than 10 polypeptides, and ferent behaviors in environments where the canola protein
noncovalent links are more important than disulfide bonds isolates are used because their respective functional proper-
for stabilization of the structural conformation. Napin con- ties are different. The different protein content profiles of
sists of two polypeptides and is stabilized primarily by canola protein isolates allow the production of any desired
disulfide bonds. Purified cruciferin showed one major 2 S/7 S/12 S protein profile for a specific application using
endothermic peak at 91 C compared with 110 C for napin mixtures of two different canola protein isolates, such as
(Wu Muir, 2008). the PMM-derived isolate and the supernatant-derived
It has been reported that low molecular weight proteins isolate.
make up 40e50% of the nitrogenous compounds in rape- Yew-Min, Levente, and Leon (1990) described a process
seed (canola) (Mieth et al., 1983). According to various au- for the production of canola protein materials by alkaline
thors, the molecular masses of these compounds range from extraction followed by precipitation and membrane pro-
12 to 18 kDa (Amarowicz, Panasiuk, Pari, 2003b). For cessing. The process consisted of the extraction of oil-
the separation of low molecular weight canola proteins, free meal at pH 10.5e12.5, isoelectric precipitation to
HPLC methods with ion-exchange columns and capillary recover proteins and ultrafiltration followed by diafiltration
electrophoresis with SDS as a surfactant have been used to concentrate and purify the remaining acid-soluble
(Amarowicz, Kolodziejczyk, Pegg, 2003a). proteins. According to the authors, these steps are comple-
mentary and yield three products with excellent protein
Canola protein production recovery. In this process, the isoelectric and soluble protein
In the United States patent application number isolates contained 87e100% protein (N Â 6.25). All pro-
20100063255 (Logie Milanova, 2008), it was reported tein fractions were free from glucosinolates, and the two
that in addition to the 12 S and 2 S proteins, the procedures types of isolates produced were low in phytate, light in
used for the isolation of canola proteins produce significant color, and bland in taste. It was reported that the isolate
quantities of a 7 S fraction, which appears to contain a new yield depended on the properties of the starting meal. The
protein. Accordingly, one aspect of the application was the precipitation, ultrafiltration and diafiltration processes
isolation and purification of the 7 S protein of canola. It was were conducted on hexane-extracted meal (with hulled
also found that the relative proportions of the 12 S, 7 S and and dehulled materials), CH3OH/NH3/H2O-hexane-ex-
2 S proteins differ between a protein micellar mass-derived tracted meal and dehulled meal. According to the reported
canola protein isolate and a supernatant-derived canola pro- information, the meal was extracted with an aqueous NaOH
tein isolate, which were prepared using industrial proce- solution at solvent/meal ratio R ¼ 18. The hexane-extracted
dures. These procedures involved a multiple step process canola meal and the commercial meal were extracted for
of extracting canola oil seed meal using a salt solution, sep- 30 min, while the CH3OH/NH3/H2O-hexane-extracted
arating the resulting aqueous protein solution from the re- meal was extracted for 2 h. The solutions were maintained
sidual oil seed meal, increasing the protein concentration either at a pH of 11.0 for hexane-extracted canola meal
of the aqueous solution to at least 20% (w/v) while main- and commercial canola meal or at a pH of 12.0 for the
taining a constant ionic strength using a selective mem- CH3OH/NH3/H2O-hexane-extracted canola meal. In addi-
brane technique, diluting the resulting concentrated tion, 1% (dry basis) Na2S03 was added to the commercial
protein solution into chilled water to induce the formation canola meal during the aqueous extraction step to prevent
of protein micelles, settling the protein micelles to form the oxidation of phenolic compounds and to produce pro-
an amorphous, sticky, gelatinous gluten-like protein micel- tein products with a lighter color and better flavor. After
lar mass (PMM), and recovering the protein-rich protein centrifugation and filtration of the liquid phase, the ex-
micellar mass from the supernatant. In the US-patent appli- tracted meal was washed twice with pH 11.0 or 12.0 water
cation number 20100063255 (Logie Milanova, 2008), at water/meal ratio R ¼ 6, and the washings were added to
the PMM canola protein isolate was characterized by a pro- the original extract. The extracted wet meal was recovered
tein content of 90% (w/w, dry basis) and consisted of about and freeze-dried to produce a residual meal. The pH of the
60e98% of the 7 S protein, about 1e15% (w/w) of the 12 S canola protein extracts was adjusted to 3.5 by the addition
protein and 0e25% (w/w) of the 2 S protein. In contrast, of 6 N HCl. After separation, the protein precipitate was
the supernatant-derived canola protein isolate was charac- washed with pH 3.5 or 4.0 water at a water-to-precipitate
terized by a protein content of 90% (w/w) and consisted (wet) ratio of 10. The washed precipitate was then freeze-
of 0e5% (w/w) of the 12 S protein, about 5e40% (w/w) dried to produce an isoelectric protein isolate. The protein
of the 7 S protein and about 60e95% (w/w) of the 2 S pro- solution was first ultrafiltered at a concentration factor
tein fraction. Thus, the protein component profiles of the (CF) of 10 and then diafiltrated at a diavolume (DV) of
two canola protein isolates were very different. In the 5. A 10-kD ultrafiltration membrane was used in both mem-
PMM-derived canola protein isolate, the predominant pro- brane processing steps. Finally, the diafiltered retentate was
tein species was the 7 S protein; however, in the freeze-dried to produce the soluble protein isolate.


Klockeman et al. (1997) reported the isolation and char- meal as reported in the literature (80e95% reported by
acterization of defatted canola meal proteins. According to Ismond Welsh, 1992; Diosady, Tzeng, Rubin, 1984;
their study, canola protein was extracted from defatted Tzeng, Diosady, Rubin, 1988a). Protein recovery values
canola meal using 5% (w/v) extraction solution of 0.4% of 87.5% were obtained as compared to literature values of
(w/v) NaOH at room temperature on an orbital shaker at 33e65% (Rohani Chen, 1993; Xu Diosady, 1994a,
180À200 rpm for 60 min. The residual solids were dis- 1994b).
carded following centrifugation at 3000 g for 20 min at Recently, the preparation of canola protein materials us-
5e10 C. Glacial acetic acid was then added to the protein ing membrane technology and the evaluation of the func-
extract to adjust the pH to 3.5 for protein precipitation. Af- tional properties of meals were reported (Ghodsvali et al.,
terward, the precipitated canola protein was separated by 2005). According to the authors, suitable conditions for
centrifugation at 3000 g for 20 min at 5À10 C. The protein the extraction and precipitation of proteins from Iranian ca-
precipitate was washed three times with distilled deionized nola (Brassica napus, cv. Quantum, PF, and Hyola) meals
water and centrifuged at 3000 g for 20 min at 5e10 C be- were determined using a membrane-based process, which
tween each wash. The final protein isolate obtained was consisted of extraction of hexane-defatted canola meals at
freeze-dried. This extraction method is summarized in pH 9.5e12.0 and precipitation at pH 3.5 and 7.5 to recover
Fig. 1. The reported method consisted of the extraction a precipitated protein isolate (PPI). An acid-soluble protein
and isolation of protein from crude commercial hexane-de- isolate (SPI) was then prepared by ultrafiltration (UF) fol-
fatted canola meal, and the authors stated that this method lowed by diafiltration (DF) and drying. The highest protein
has a significantly increased protein extraction capacity and yields were obtained by alkaline extraction at pH 12.0 for
a higher protein recovery. In their study, a proximate anal- all meals investigated. The maximum yield of precipitated
ysis revealed that the hexane-defatted canola meal con- protein was observed at pH values between 4.5 and 5.5 and
tained 12.3% moisture and 32.1% protein, 8.2% ash, depended on the variety and dehulling treatment. Almost
4.4% fat, and 55.4% carbohydrate on a dry weight basis. 90% of the proteins were recovered in three fractions: the
The majority of the protein was soluble when dispersed PPI, SPI (81e98% protein, N*6.25), and the meal residue
in 0.4% NaOH or 5% NaCl. This solubility profile indicates (35% protein). The glucosinolate contents of all meals
that the isolated canola proteins are primarily glutelins and tested and the protein fractions were low, and some samples
globulins. Protein extraction in all concentrations of NaOH were below the detection limit for glucosinolates. Both iso-
was significantly increased if baffled flasks were used; lates were low in phytic acid content. In the work of
95.2e99.6% of the total protein in the meal was extracted Ghodsvali et al. (2005), the alkaline extraction was con-
in 0.4% (w/v) NaOH. The maximum protein extraction was ducted by dispersing the canola meal in distilled water at
obtained with a 5% (w/v) meal ratio and incubation in 0.4% room temperature for 30 min. The pH of the extraction so-
(w/v) NaOH for 60 min at 180e200 rpm. This represents lution was adjusted to a predetermined level and main-
an increase in protein extraction from defatted canola tained by the addition of aqueous 5% NaOH as required.
The authors reported that an appropriate concentration of
1e6 N NaOH solution was selected to avoid excessive di-
lution during pH adjustment. A pH range between 9.5 and
12.0 was examined in increments of 0.5 pH units. The
slurry was centrifuged at 5000 rpm for 15 min, and the su-
pernatant was filtered. The meal residue was washed twice
with an aqueous alkali solution (R ¼ 6) with the same pH as
the extraction solution and oven-dried overnight. According
to the authors, pH 12.0 was used in subsequent precipita-
tion tests. For the isoelectric precipitation of canola pro-
teins from the alkaline extract, the isoelectric points were
determined. Meals were extracted with 5% NaOH at pH
4.5 and a solvent-to-meal ratio of 18. The alkali solution
was acidified with HCl (6 M) to obtain pH values between
3.5 and 7.5 in increments of 0.5 pH units. After centrifuga-
tion at 5000 rpm for 20 min, the supernatant was filtered
using filter paper, and the precipitate was washed with wa-
ter acidified to the precipitation pH at a water-to-precipitate
(wet) ratio of 10, centrifuged again and oven-dried over-
night. Membrane separation was conducted in an ultrafiltra-
tion unit in the diafiltration mode. A built-in peristaltic
Fig. 1. Schematic representation of canola meal protein isolate extrac- pump drew the solution from a sample container and
tion method (from Klockeman et al., 1997). pumped it through the hollow fiber cartridge. The


membrane used had a nominal molecular weight cutoff of found in lower proportions in the permeate. The opposite
10 kDa and a membrane area of 0.1 m2. The obtained per- trend was observed for basic peptides, whereas neutral
meate consisted of water and dissolved low-molecular peptides were found in the same proportion in the retentate
weight components. The retentate was returned to the sam- and permeate. The authors explained this behavior based
ple container. A soluble canola protein isolate was prepared on the Donnan theory and the existence of electrostatic in-
with the same process described by Tzeng et al., (1988b), teractions (attractive and repulsive forces) at the membra-
which consisted of four major operational stages: alkaline neesolution interface. Selectivity between basic and acid
extraction and washing, isoelectric precipitation and wash- peptides was as high as 1.90 at pH 9 and low ionic strength.
ing, ultrafiltration and diafiltration. Hexane-extracted meals A membrane-based process was proposed for the fraction-
were tested, and each meal was extracted at pH 12.0. The ation of rapeseed peptide mixtures (Tessier et al., 2006).
extract was combined with all washes, and CaCl2 (15%,
by weight of the starting meal) was added to the protein ex-
tract. The pH was then reduced to the isoelectric point by Canola protein functional properties
the addition of 6 N HCl. The pH was maintained for Water absorption capacity (WAC)
15 min to allow protein aggregation, and then the suspen- Khattab and Arntfield (2009) studied the water absorp-
sion was centrifuged. The supernatant was filtered, and af- tion capacity of canola proteins and reported that the en-
ter separation, the protein precipitate was washed with 10 hanced ability of canola meal to absorb and retain water
times its weight of distilled water and centrifuged. The su- improved the water binding capacity of the food product,
pernatant and all washes were combined and ultrafiltered at enhanced its flavor retention, improved its mouthfeel and
a CF of 10, followed by diafiltration at a DV of 5. reduced the moisture of food products. In their study, the
A more attractive approach for the valorization of canola water absorption capacities of raw and treated meals were
(rapeseed) proteins consists of the production of different reported, and it was shown that the treatment of the meal
peptide fractions by enzymatic hydrolysis followed by had a significant effect on the WAC. Canola meal was
membrane filtration (fractionation). In this context, a recent able to absorb 390% of its initial weight, and its WAC
study reported the selective separation of peptides was higher than soybean meal, which absorbed 303% of
contained in a rapeseed (Brassica campestris L.) protein its initial weight, but lower than flaxseed meal. This result
hydrolysate using ultrafiltration/nanofiltration (UF/NF) agreed well with Wanasundara and Shahidi (1994), who
membranes (Tessier, Harscoat-Schiavo, Marc, 2006). In found that the WAC of flaxseed meal was considerably
this study, the ability of a charged ultrafiltration (UF) mem- higher than that of canola. These results agree with those
brane to fractionate the small peptides found in a rapeseed reported for canola meal by Naczk, Diosady, and Rubin
protein enzymatic hydrolysate based on charge characteris- (1985) and Ghodsvali et al. (2005), who showed that the
tics was investigated. Because the peptide mixture obtained water absorption capacities of canola meals vary with ca-
after enzymatic hydrolysis was heterogeneous and difficult nola cultivar (variety) and dehulling treatment. For canola
to separate, the authors proposed an original approach that meals, values between 218% and 382% have been reported.
required the development of technological alternatives for However, it is important to take in consideration that the ca-
more efficient separation of the numerous peptide species. nola meals used in the literature contained considerable
In this study, a preliminary step consisted of precipitation amounts of fiber, which can enhance the overall water hold-
followed by filtration with a 3-kDa molecular weight cutoff ing capacity, and studies on the water holding capacity of
(MWCO) membrane to obtain a concentrated solution of canola protein isolates would be more relevant. This agrees
small peptides. The feasibility of fractionating these small with the information reported by Wanasundara and Shahidi
peptides with a charged 1-kDa MWCO membrane was (1994), who stated that the higher water adsorption of sol-
also investigated. According to this study, this approach al- vent-extracted oil seed meals may be due to the presence of
lowed an estimation of the contribution of electrostatic in- hull polysaccharides. Sosulski, Humbert, Bui, and Jones
teractions during membrane fractionation. Moreover, the (1976) studied the water absorption properties of rapeseed
effect of solution pH and ionic strength on peptide trans- flours and isolates and reported that the WHC of these in-
mission was studied. The ionic strength contribution was gredients exceeded 200% and compared favorably with
considered by studying its effect on the selectivity of a de- that of soybean flour. Manamperi, Pryor and Chang
salting step by nanofiltration on a 0.5-kDa MWCO nanofil- (2007) separated and evaluated canola meal and protein
tration membrane. It has been reported that peptide for industrial bioproducts and found that the water absorp-
transmission was lower at pH 9 than at pH 4 and the lowest tion capacity of canola meal exceeded 250%; their result
at pH 9 and with low ionic strength. The ionic strength had agrees with values reported for different varieties of canola
a significant effect at pH 9 but showed no effect at pH 4. meal, which ranged from 209% (Ghodsvali et al.., 2005) to
This difference could be attributed to the different ionic 382% (Naczk et al., 1985). Mahajan, Dua, and Bhardwaj
species that acted as counter-ions during membrane filtra- (2002) reported a study in which dry and swollen canola
tion. The amino acid analysis and capillary electrophoresis seeds were defatted with hexane, and the freeze-dried pow-
revealed that negatively charged (acidic) peptides were der was analyzed for the functional properties of the meals.


The results showed that the water absorption capacity of the applications where a high water holding capacity is re-
swollen rapeseed meal was higher than dry meal. quired, the situation is quite different because solubility is
generally negatively correlated with water holding capacity.
Oil/fat absorption As reported by Prinyawiwatkul, Beuchat, McWatters,
The fat-adsorption capacity of any food compound is Phillips (1997), protein solubility can be considered as
important for food applications because it relies mainly the most important property because it affects other proper-
on its capacity to physically entrap oil by a complex capil- ties, such as emulsification ability, foam-forming capacity
lary-attraction process. In many food applications, such as and gel formation. Recently, Khattab and Arntfield (2009)
emulsion-type meat products, the ability of a food compo- studied the functional properties of raw and processed ca-
nent to entrap oil is an important characteristic because fat nola meals and showed that canola meal had a protein sol-
acts as a flavor retainer, a consistency trait and an enhancer ubility (expressed as nitrogen solubility) of 66.42%. At the
of mouthfeel (Khattab Arntfield, 2009). The fat absorp- same time, they compared canola meal protein solubility
tion capacity of canola meal was studied and compared with soy and flaxseed meals, which have protein solubilities
with those of soy and flaxseed meals (Khattab of 74.00% and 56.50%, respectively. The results obtained
Arntfield, 2009). It was reported that significant differences in this study were comparable with those reported in the lit-
in the oil absorption capacities were noted among the erature (John Baize, 1999; Madhusudhan Singh, 1985;
above-listed meals and that soy meal had the highest value, Wanasundara Shahidi, 1994). As reported in Khattab and
which was followed by canola and flaxseed meal, respec- Arntfield (2009), canola meal protein solubility was signif-
tively. In general, the fat absorption capacity depends on icantly reduced after heat treatment, which consisted of dry
several properties, such as powder particle size and surface roasting and boiling in water. The two treatments caused
tension. In addition, the fat absorption capacity is nega- 29.07% and 25.61% solubility reductions, respectively.
tively correlated with water absorption capacity. This state- The protein solubilities of soy and flaxseed meals were re-
ment agrees with the information reported by Naczk et al. duced by 33.69% and 46.27%, respectively, after dry roast-
(1985) and Ghodsvali et al. (2005), who reported canola ing treatment and 43.00% and 39.40%, respectively, after
meal oil absorption and water holding capacity values of boiling. Protein denaturation during heat treatment could
188e203 and 265.5e281.5%, respectively. The oil absorp- explain the solubility reduction. Heat treatment could en-
tion capacity can be modulated by different treatments, and hance the exposure of hydrophobic residues, which contrib-
it was reported that heat treatments increased the oil ab- ute to the reduction in the overall protein solubility.
sorption capacities of different oil seed meals, including ca- Electrostatic repulsion and ionic hydration that occur at dif-
nola. Among heat treatments, boiling was reported to ferent pHs can also affect protein solubility (Moure,
produce the greatest enhancement. The phenomenon of in- Sineiro, Dom ınguez, Paraj, 2006). Klockeman et al.
o
creasing fat absorption after heat treatment has been asso- (1997) reported the extraction and isolation of proteins
ciated with the heat dissociation of proteins and from canola oil processing waste. They showed that canola
denaturation, which is hypothesized to unmask non-polar proteins had poor solubility between pH 2 and 10 for all
residues in the interior of the protein molecules (Kinsella dispersion solutions used. The solubility of the protein iso-
Melachouris, 1976, pp. 219e280). In a report by lates was 60% or less. The low solubility could be attrib-
Mahajan et al. (2002), dry and 24-h swollen rapeseeds uted to the extraction conditions used. Radwan and Lu
were defatted with hexane, and the freeze-dried powder (1976) studied the solubility of the proteins of the dehulled
was analyzed. It has been reported that the fat absorption and defatted ‘Tower’ variety of rapeseed (canola) in aque-
capacity of swollen rapeseed meal is higher than that of ous solutions at 25, 35, 45, and 55 C and at pH 1e13. Ac-
the dry meal. Gruener and Ismond (1997) reported the iso- cording to this study, the minimum solubilities occurred at
lation of a canola protein concentrate with improved func- pH values of 4.5, 4.8, 7.0, and 7.2, respectively, for the four
tional properties; in their method, the canola 12 S globulin temperatures tested. These differences could be attributed
was isolated by the protein micellar mass procedure (PMM) to the different pHs that were used to precipitate the differ-
and modified by acetylation and succinylation. It was ent protein fractions. Paulson and Tung (1989) studied the
shown that the emulsion stability significantly increased effects of succinylation (54% and 84% modification of free
initially and then decreased at the highest levels of modifi- amino groups) in the pH interval of 3.5e11.0 and NaCl
cation. Following acylation, the fat absorption capacity was concentrations up to 0.7 M on the solubility of a canola pro-
significantly elevated. tein isolate. According to this study, succinylation mark-
edly enhanced the protein solubility at alkaline and
Protein/nitrogen solubility slightly acidic pH values, while the effect of NaCl concen-
For food applications, protein (nitrogen) solubility is an tration depended on the pH value. This might be related to
important parameter that influences the extent of applica- the effect of succinylation on surface hydrophobicity
tions in different food matrices. In some cases, such as (Paulson Marvin, 1987), which decreases as the level
beverages, high protein solubility is a determinant for of succinylation increases. This can be confirmed by Zeta
application as a fortification ingredient. In other potential values, which became more electronegative as


both succinylation and pH increased but decreased with the stability, and textural properties of a protein-fat-water sys-
addition of NaCl. Depending on the pH, addition of salt to tem. It is also important to ensure that the technique used to
a protein suspension can affect the net charge density of the evaluate emulsifying properties is adequate. In the work of
proteins and thus modify the solubility by enhancing or re- Khattab and Arntfield (2009), the emulsifying capacity of
ducing inter-molecular repulsions. In Gruener and Ismond canola proteins (meal) was expressed as the maximum
(1997), the canola 12 S globulin was isolated using the pro- amount of oil that the meal solution would emulsify with-
tein micellar mass procedure (PMM) and modified by acet- out losing its emulsion characteristics. According to the
ylation and succinylation to obtain a canola protein reported results, the investigated canola meal showed
concentrate with improved functional properties. It has significantly higher EC values compared with those of
been shown that protein solubility below the isoelectric soy and flaxseed meals. However, they also reported that
point of the PMM was impaired, but the solubility at neu- roasting and boiling caused significant reductions in the
tral to alkaline pH values was greatly enhanced. Based on ECs of these meals. They explained that that high protein
the information on canola protein solubility, it is possible solubility (Kinsella Melachouris, 1976, pp. 219e280)
to highlight one parameter that contributes to the solubility and high fat-adsorption capacity were positively correlated
of purified isolates: the predominance of low molecular with the ability to form and stabilize emulsions. They also
weight species (Fig. 2). stated that the lower EC values of boiled canola meal might
be due to its low nitrogen solubility. Similarly, the degree of
Emulsifying properties heating was also reported to be a determinant for the reduc-
In food applications, such as emulsion-type meat prod- tion of the emulsifying capacity of legume proteins in gen-
ucts, salad dressings and mayonnaise, emulsifying proper- eral (Eke Akobundu, 1993). Dev and Mukherjee (1986)
ties of canola proteins is an important attribute and have reported that rapeseed products generally have lower
largely defines the extent of use of this ingredient to stabi- emulsifying capacities but higher emulsifying stabilities
lize food systems. Several studies have been conducted in than soy products, although the processing treatment can
the past two decades on the feasibility of using canola pro- alter this trend. Isolates tend to have improved emulsifying
teins in emulsion-type foods. Recently, Khattab and properties as compared to concentrates (McCurdy, 1990).
Arntfield (2009) studied the emulsification ability of canola Recently, a fundamental study examined the emulsifying
meal using two parameters: emulsifying capacity (EC) and properties of the two major canola proteins cruciferin and
stability (ES). They showed that both properties are func- napin. It has been reported that the emulsion prepared
tions of the protein concentration, pH, and ionic strength. with cruciferin showed a significantly higher specific sur-
They also related these properties to the viscosity of the face area and a lower particle size than that of napin. The
system, but this parameter (viscosity) was function of the study reported by Wu and Muir (2008) indicated that the
mentioned above conditions. Indeed, emulsion is a complex presence of napin could detrimentally affect the emulsion
system that involves a multitude of chemical and physical stability of canola protein isolates (Wu Muir, 2008).
phenomena, which play different roles in the formation, The emulsifying ability of canola proteins was studied
in combination with hydrocolloids. A study investigated
the properties of commercial canola protein isolatee
hydrocolloid-stabilized emulsions under varied conditions,
such as different canola protein isolate concentrations,
amounts of salt and hydrocolloid added, pH values of the me-
dium and the presence of denaturants (Uruakpa Arntfield,
2005). In this study, the emulsifying activity index (EAI)
and emulsion stability (ES) were determined by a turbidimet-
ric method. According to the authors, the obtained results
showed that under conditions that promote complex formation
between the proteins and hydrocolloids, which included pH 6
and the addition of 1% (w/v) k-carrageenan, the EAI of CPI-
stabilized emulsions increased from 162 to 201 m2/g and the
ES increased from 68% to 95%. Under conditions that pro-
mote incompatibility between canola proteins and the hydro-
colloid (pH 10), the use of 1% (w/v) guar gum increased the
EAI of CPI-stabilized emulsions from 68 to 177 m2/g and
the ES from 66% to 100%. The lower EAI and ES values ob-
served in the hydrocolloid-stabilized CPI emulsions treated
Fig. 2. SDS-PAGE of canola protein (from Ebrahimi, Nikkhah, Sadeghi. with sodium salts and denaturants support the involvement
Raisali, 2009). Lane 1 is the standards and Lane 2 is the canola/ of hydrophobic interactions, hydrogen bonds and disulfide
rapessed proteins. linkages in the emulsification of these systems. It was also


shown that the interfacial properties of CPIehydrocolloid degree of hydrolysis (DH) increased. The authors con-
complexes were improved by electrostatic complex cluded that hydrolysates with an increased degree of hydro-
formation and thermodynamic incompatibility, making lysis are apparently capable of foaming but lack the
these systems suitable for stabilizing food emulsions, such strength to maintain the foam as a result of the reduction
as salad dressings and mayonnaise (Uruakpa Arntfield, in protein molecular weight. The foam stability of the pro-
2005). tein isolates dropped to 0% after 15 min of hydrolysis
(Vioque, Snchez-Vioque, Clemente, Pedroche, Milln,
a a
Foaming properties 2000).
In many food applications, because the surface area in
the liquid/air interface increases, proteins denature and ag- Gelling ability
gregate during whipping. Air entrapment plays a major role In general, all proteins can form a gel, but differences
in different food matrices and is important for flours used in exist in the gel strengths. The ability of proteins to form
many leavening food products, such as breads, cakes and gels can be measured by the determination of the least ge-
cookies (Sreerama, Sasikala, Pratape, 2008). The foam- lation concentration, which is defined as the minimal pro-
ing capacity of canola meal was studied and compared tein concentration needed to produce a gel that does not
with soy and flaxseed (Khattab Arntfield, 2009). They slide down the walls of an inverted tube (Moure et al.,
showed that the foam capacities and stabilities of raw and 2006). Khattab and Arntfield (2009) studied the least gela-
treated canola meal were higher than those of soy and flax- tion concentrations of raw and heat-treated canola meals
seed meals. They expressed the foaming capacity as a per- and reported that neither roasting nor boiling caused a sig-
centage and reported values of 56.44%, 44.56% and nificant increase in the least gelation concentration of dif-
17.82%, for canola, soy and flaxseed meal, respectively. ferent canola meals. This is supported by reports in the
It was shown that heat treatment significantly reduced scientific literature, which show that the gelation of proteins
both the foaming capacity and foam stability of the differ- increases with molecular weight (size) because large mole-
ent meals, including canola meal. The authors explained cules form extensive networks by cross-linking in three
that this reduction was mainly related to protein denatur- dimensions (Oakenfull, Pearce, Burley, 1997). Compared
ation; this conclusion agrees with the data reported by with soy and flaxseed meals, canola meal required the high-
Lin, Humbert, Sosulski, 1974, who stated that a native est concentration for gelation regardless of the treatment
protein gives a higher foam stability than a denatured used.
one. Gruener and Ismond (1997) conducted a study in To improve the function of canola proteins in gel-like
which the canola 12 s globulin was isolated by the protein food systems, different additives can be combined with these
PMM and modified by acetylation and succinylation to im- proteins to make convenient gels. In this context, a study has
prove the functional properties of the canola protein con- been reported in which the thermogelation properties of a ca-
centrate. The PMM foaming capacity was significantly nola protein isolate in a mixed system with k-carrageenan (k-
increased by acylation, and the foam stability decreased CAR) were studied using dynamic rheological testing. The
significantly after acylation. They concluded that in general gel properties were evaluated under different conditions,
the acylated concentrates possessed improved functionality such as pH, NaCl, and k-carrageenan and canola protein iso-
as compared to the PMM, which makes them more suitable late concentrations. The factorial and response surface opti-
as a food ingredient. Xu and Diosady (2002) studied the mization models were used to identify the processing
functional properties of Chinese rapeseed meals and re- conditions that would result in CPIek-CAR gels with max-
ported that Chinese rapeseed meals foams were more stable imized G0 values (!44,000 Pa) and minimized tan d values
than those of the canola meals prepared by Naczk et al. (0.01e0.11). According to the results, it was found that
(1985). Moreover, they showed that Chinese rapeseed pro- canola proteinecarrageenan gel formation was strongly
tein isolates were characterized by excellent whippability. pH-, salt (NaCl)- and k-carrageenan concentration-depen-
They found that the foaming properties of the soybean iso- dent (Uruakpa Arntfield, 2004). The reported results indi-
late were between those of the rapeseed meals and rapeseed cated that the optimum conditions for CPIek-CAR gels
protein isolates. The difference between a meal and an iso- were pH 6, 0.05 M NaCl, 3% k-CAR and 15% CPI. Samples
late is the protein content, which is obviously higher in an prepared at pH 6 showed high G0 (95,465 Pa) and low
isolate. All foams were stable and lasted for more than 2 h. tan d (0.15) values. High G0 values indicate stronger inter-
The foaming properties of canola protein were evaluated as molecular networks and increased proteineprotein and pro-
a function of degree of protein hydrolysis. Limited canola teinepolysaccharide interactions, while low tan d values
protein hydrolysates ranging from 3.1% to 7.7% hydrolysis indicate a more elastic network. A synergistic behavior be-
were produced from an isoelectrically precipitated protein tween CPI and k-CAR was observed with superior network
isolate. It has been shown that all canola protein hydroly- strength (high G0 values) for the mixed gels at temperatures
sates have lower foam stabilities than those reported in above 80 C. Furthermore, the gels showed improved net-
the literature for other rapeseed protein products work structure (low tan d values) during the heating and
(Frokjaer, 1994), and the foam stability decreased as the cooling phases. The canola proteinek-carrageenan mixtures


exhibited very strong and elastic networks, indicating that 1998). Paulson and Tung (1989) studied the thermally in-
CPI can serve as a structuring agent in mixed food systems duced gelation of a rapeseed (canola) protein isolate heated
(Uruakpa Arntfield, 2004). to 72 C. Gels were formed only at high pH (9.5). Lger e
Canola proteins have been considered as potential ingre- and Arntfield (1993) studied the gelation of 12 S canola glob-
dients for food applications where a gel-like structure is de- ulin. Gels prepared with 6% protein under alkaline condi-
sired. In a recent study, enzymatic modification with tions were superior to gels prepared from acidic solutions.
transglutaminase (TG) was used to enhance the gelation The effects of pH, salts, and denaturing and reducing agents
of a canola protein isolate and thus improve its potential on the gelation properties led the authors to conclude that
as a food ingredient. Different parameters, such as the ef- hydrophobic forces and electrostatic interactions were re-
fects of canola protein isolate concentration, transglutami- sponsible for establishing the gel network, while gel stabili-
nase (TG) concentration, and treatment temperature and zation and strengthening were attributed to disulfide bonds,
time, have been studied to determine their effects on canola electrostatic interactions, and hydrogen bonding. Succinyla-
protein isolate gelation properties. Different techniques, tion was used to improve the gel-forming properties of a can-
such as texture analysis, sodium dodecyl sulfate-polyacryl- ola protein isolate by Paulson and Tung (1989). In this study,
amide gel electrophoresis (SDS-PAGE) and scanning elec- the pH range of gel formation was extended from the alkaline
tron microscopy, were used to characterize the resulting region (pH 9.5) to slightly acidic pHs (5.0). Although sev-
canola protein isolate networks. It has been reported that eral studies have analyzed the gelling ability of canola
the protein concentration, amount of transglutaminase proteins, it is well recognized that comparison of the gel-
(TG), and treatment temperature significant affected gel forming properties of the different canola protein prepara-
strength. According to the authors (Pinterits Arntfield, tions is difficult. This is principally because there are major
2008), gelation was improved by increasing the amounts differences the compositions and purities of the proteins.
of protein and TG while keeping the treatment temperature Therefore, studies in which pure fractions and known
close to 40 C. SDS-PAGE showed that subunit cross-link- combinations must be conducted bettering increase the
ing occurred during TG treatment, which thus explained the understanding of the canola protein behavior in relation to
increase in gel strength observed during texture analysis. gel formation. In this context, the study reported by
The above-mentioned effects were also confirmed by Gruener and Ismond (1997), which the canola 12 S globulin
microscopy (Pinterits Arntfield, 2008). was isolated by the protein PMM and modified by acetylation
Schwenke, Dahme, and Wolter (1998) reported the gel- and succinylation, showed that the gelation properties of ca-
forming abilities of a rapeseed (canola) protein isolate, which nola proteins were generally improved by acylation. Further-
was composed of 70% globulin (cruciferin) and 30% albu- more, the acylated concentrates were significantly lighter in
min (napin), and their individual protein components. In color than the original PMM.
this study, the influence of acetylation upon the gelation
properties was also studied. The highest gel strength (mea- Bioactive compounds from canola proteins
sured as shear modulus) of the isolate was obtained at pH The increase in consumer awareness about healthy foods
values around 9, which is between the isoelectric points of has encouraged researchers to identify bioactive natural
the major proteins. Moreover, purified cruciferin gave the components in different products (Murty, Pittaway,
highest shear modulus values, with maxima at pH 6 and 8. Ball, in press). Canola proteins are considered to be attrac-
Weak and poorly stable gels that exhibited strong hysteresis tive and promising sources of bioactive compounds.
were obtained with isolated napin. The authors also reported Recently, a number of research works have focused on
that acetylation resulted in a pH shift of the shear modulus the investigation of different methods to produce active
maximum of the protein isolate to about 6. The gelation tem- peptides from the enzymatic hydrolysis of canola proteins.
perature of the acetylated isolate was more dependent on pH Angiotensin-I Converting Enzyme (ACE) inhibitory activ-
and concentration compared with the other proteins ity, antioxidant activity, bile acid-binding capacity, anti-
(Schwenke et al., 1998). Because of the increasing demand thrombotic activity and cell growth effects have been
for plant proteins in gel-like products, the ability to form identified as bioactive characteristics of canola/rapeseed
gels, which is a key functional property of plant proteins, proteins (Table 2).
has been extensively studied in the past two decades. Gill
and Tung (1978) first demonstrated the ability of a highly ACE inhibitory activity
glycosylated 12 S rapeseed (canola) protein to form gels dur- Blood pressure is controlled by a regulatory hormonal
ing heating at pH 4. The strongest gels were formed at high mechanism known as the “renin angiotensin system.” The
pH and ionic strength conditions. The high carbohydrate regulatory mechanism takes place in the kidneys, where
contents of the canola meal (12.9%) led the authors to pro- the hydrolytic enzyme renin is secreted. Hence, plasma an-
pose that proteinecarbohydrate interactions occurred during giotensinogen is hydrolyzed to a decapeptide called Angio-
gel formation. It was also reported that the viscosity of a hex- tensin I, which is subsequently hydrolyzed by Angiotensin
ametaphosphate-extracted rapeseed protein isolate heated to Converting Enzyme (ACE) to form Angiotensin II, which is
80 C increased, but it did not form a gel (Schwenke et al., a vasoconstricting octapeptide that elevates the blood


Table 2. Bioactivity of rapeseed proteins and hydrolysates

Bioactivity Rapeseed proteins/hydrolysates References
ACE inhibitory activity Subtisilin hydrolysates of the protein isolate (purification of Yamada et al., 2010.
rapakinin Arg-Ile-Tyr)
Hydrolysates of the defatted meal obtained by enzymatic treatment Wu et al., 2009.
with: Umamizyme; Proteases A, P, R, M and S Amano; Proleather
FG-F; Alcalase 2.4L; Enzeco alkaline protease L-FG; Enzeco
neutral protease NBP-L; Pepsin, Trypsin and Chymotrypsin-TLCK
Alcalase 2.4L hydrolysate of the protein isolate Megias et al., 2006,Wu Muir, 2008.
Alcalase 2.4L hydrolysate of the defatted meal (purification of Val- Wu et al., 2008
Ser-Val and PheeLeu located in napin and cruciferin, respectively)
Alcalase 2.4L hydrolysates of the protein isolate, napin and Wu Muir, 2008.
cruciferin
Protein isolate Yoshie-Stark et al., 2008.
Pepsin and Pepsin/Pancreatin hydrolysates of the protein isolate
Antioxidant properties Alcalase/Flavourzyme hydrolysate of the albumin isolate Xue et al., 2009.
Alcalase 2.4L hydrolysate of the flour (purification of Pro-Ala-Gly- Zhang et al., 2008; Zhang et al., 2009.
Pro-Phe corresponding to the sequence 38e42 of napin).
Protein isolate Yoshie-Stark et al., 2008.
Pepsin and Pepsin/Pancreatin hydrolysates of the protein isolate
Bile acid-binding capacity Protein isolate Yoshie-Stark et al., 2008.
Pepsin and pepsin/pancreatin hydrolysates of the protein isolate
Anti-thrombotic activity Alcalase 2.4L hydrolysate of the rapeseed slurry from a wet-milling Zhang et al., 2008
Effect on cell growth Alcalase, Esperase, Neutrase, Orientase and Pronase hydrolysates Chabanon et al., 2008;
of the protein isolate Farges-Haddani et al., 2006;
Farges et al., 2008.

pressure (Chen et al., 2009). Furthermore, ACE also con- 18.1 to 82.5 mg protein/mL. The differences in the ACE-in-
tributes to vasoconstriction by the degradation of bradyki- hibitory activities of the various protein hydrolysates re-
nin, a vasodilator. Consequently, the inhibition of ACE flected the different enzyme specificities. In this study,
could be an alternative method to lower blood pressure ion-exchange chromatography was used to purify specific
(Chen et al., 2009). fractions of canola protein hydrolysate, and this approach
Defatted canola meals from seeds that were processed yielded an increase in the protein content to more than
with different methods were hydrolyzed by Alcalase to pro- 95% without loss of ACE-inhibitory activity. According
duce hydrolysates that inhibited ACE activity (Megias to this study, this fraction was resistant to degradation by
et al., 2006; Wu, Aluko, Muir, 2009). Heat-treated meals gastrointestinal enzymes and ACE during in vitro incuba-
yielded protein hydrolysates with 50% ACE-inhibitory con- tion (Wu, Aluko, Muir, 2008). Specific canola protein
centrations of 27.1 and 28.6 mg protein/mL compared with fractions were also used to produce hydrolysates. Cruci-
35.7 and 44.3 mg protein/mL for the non-heat treated meals. ferin and napin hydrolysis yielded peptide fractions that
In this study, separation of the hydrolysate on a Sephadex showed potent angiotensin I-converting enzyme inhibitory
G-15 gel permeation column (GPC) yielded a fraction activity in vitro (IC50 0.035 and 0.029 mg/mL, respec-
with an IC50 value of 2.3 mg protein/mL. From a fundamen- tively), but these activities were weaker than that of the ca-
tal point of view of the mechanism of action, amino acid nola protein isolate hydrolysate (IC50 0.015 mg/mL) (Wu
analysis showed that the GPC fraction contained 45% aro- Muir, 2008). This behavior can be attributed to the syner-
matic amino acids in comparison to 8.5% in the raw hydro- getic effect of different fractions of raw canola protein
lysate. In particular, two peptides with the primary hydrolysate.
compositions Val-Ser-Val and PheeLeu were purified and On the other hand, the in vivo anti-hypertensive proper-
located in the primary structures of the napin and cruciferin ties of rapeseed proteins have been also reported by
native proteins. It has thus been suggested that the canola Yamada et al. (2010). Thus, an ACE-inhibitory peptide
protein hydrolysate should be considered as a potential in- called rapakinin (Arg-Ile-Tyr), which had an IC50 of
gredient for the formulation of hypotensive functional 28 mM, was isolated from the subtisilin-digested rapeseed
foods (Wu et al., 2009). To simplify the method of ACE-in- proteins. Rapakinin induced vasorelaxation with an EC50
hibitory peptide production, defatted canola meal was sub- of 5.1 mM in the mesenteric artery of spontaneously hyper-
jected to enzymatic proteolysis with different enzymes, and tensive rats (SHRs). Hence, the mechanism of vasorelaxa-
it was found that Alcalase 2.4 L and protease M “Amano” tion was elucidated, and it has been suggested that the
were the most effective enzymes for the production of anti-hypertensive activity of rapakinin might be mediated
ACE-inhibitory peptides from canola proteins. The IC50 by the PGI(2)-IP receptor, followed by CCKeCCK(1)
values of the canola protein hydrolysates ranged from receptor-dependent vasorelaxation.


Antioxidant properties W€sche (2008) have shown that rapeseed protein isolates,
a
The production of free radicals leads to many health dis- which were obtained either by iso-precipitation or ultrafiltra-
orders due to the damage they cause to biological macro- tion, and their hydrolysates, which were obtained by pepsin
molecules, especially DNA. Therefore, many natural and pepsin/pancreatin digestions, were able to bind to bile
antioxidants have been used to prevent peroxidation pro- salts. In that study, the concentration of the bile salts used
cesses (Kim Wijesekara, 2010). Xue et al. (2009) inves- was of 1.5 mM, which corresponds to the physiological con-
tigated the possible conversion of insoluble rapeseed meal centrations of bile acids in the human body (1.5e7 mM). The
protein into functionally active ingredients for food appli- results showed that 5.77%e12.6% of sodium cholate and so-
cations. The rapeseed meal protein isolates were digested dium deoxycholate were bound by the rapeseed precipitated
with Alcalase and Flavourzyme, and the resultant rapeseed protein isolate and hydrolysates, whereas ultrafiltered rape-
crude hydrolysate (RSCH) exhibited dose-dependent reduc- seed protein isolate and hydrolysates bound 5.81% to
ing antioxidant activities and hydroxyl radical scavenging 22.8% of the bile salts (Yoshie-Stark et al., 2008). Neverthe-
abilities. The RSCH also inhibited malonyldialdehyde less, neither the sodium cholate- nor the sodium deoxycho-
(MDA) generation by 50% in blood serum at 150 mg/ late-binding capacities were significantly affected by
mL. The RSCH was further separated into three fractions hydrolysis with pepsin and pepsin/pancreatin, suggesting
(RSP1, RSP2, and RSP3) by Sephadex gel filtration accord- that some large molecular weight protein fractions and undi-
ing to molecular weight. The amino acid compositions and gested polypeptides are also able to bind the ligands. A sim-
antioxidant potentials of the fractions were assessed, and it ilar lack of a direct association between hydrolysis and bile
has been reported that all three fractions showed inhibition acid-binding capacity has been observed in other plant
of superoxide anion generation to various extents. They proteins and hydrolysates (Yoshie-Stark W€sche, 2004;
a
also inhibited the autohemolysis of rat red blood cells and Ma Xiong, 2009).
MDA formation in a rat liver tissue homogenate (Xue
et al., 2009). In another study, the antioxidative capacity Anti-thrombotic activity
was observed for rapeseed peptides obtained by Alcalase Thrombosis is an anomaly in blood coagulation that is
hydrolysis (Zhang, Wang, Xu, 2008). The median effec- generally caused by blood hyperviscosity, platelet hyper-re-
tive dose (ED50) values of the three peptide fractions for activity, a high level of hemostatic proteins, such as fibrin-
a,a-diphenyl-b-picrylhydrazyl (DPPH) radical scavenging ogen, and defective fibrinolysis. Thus, antithrombotics
activity were between 41 and 499 mg/mL; for the inhibition reduce the risk of thrombosis mainly by the reduction of
of lipid peroxidation in a liposome model system, the ED50 platelet aggregation and the enhancement of fibrinolysis
values were between 4.06 and 4.69 mg/mL, which are com- (Erdmann, Cheung, Schr€der, 2008).
o
parable to that of ascorbic acid at 5 mg/mL (Zhang et al., The anti-thrombotic activity of crude rapeseed peptide
2008; Zhang, Wang, Xu, Gao, 2009). Moreover, the fractions prepared from an aqueous extraction of rapeseed
most antioxidative peptide was identified by LC-MS/MS proteins digested with Alcalase 2.4 L has been observed
as Pro-Ala-Gly-Pro-Phe, which corresponds to amino acid (Zhang et al., 2008). The anti-thrombotic peptide fractions
residues 38e42 of napin (Zhang et al., 2009). were analyzed in terms of their amino acid content, and the
The results suggest that rapeseed protein hydrolysates results showed that they were rich in His, Pro, Trp, Tyr,
could be useful as a human food additive and a source of Met, Cys, and Phe. Furthermore, the rapeseed bioactive
bioactive peptides with antioxidant properties (Xue et al., peptide fractions had significant inhibitory activities on
2009). the thrombin-catalyzed coagulation of fibrinogen, which
is considered to be a key step in the formation of fibrin clots
Bile acid-binding capacity and therefore thrombosis. Although the inhibitory effect
Hypercholesterolemia is characterized by the accumula- was not dose dependent, 90% inhibition was observed
tion of LDL (low-density lipoprotein) cholesterol in the with peptide concentrations between 30 and 50 mg/mL.
blood vessels and is considered as a major cause of heart However, the anti-thrombotic effects observed were weaker
diseases and atherosclerosis (World Health Organization, than that of heparin, which possessed a dose-dependent ef-
2009). However, hypercholesterolemia can be prevented fect and an ED50 value of 0.07 mg/mL (Zhang et al., 2008).
by exercise, a healthy diet and the consumption of bile
acid sequestrants, which are better known as hypolipidemic Effects on cell growth
agents (Anderson Siesel, 1990). Plasma cholesterol Rapeseed protein hydrolysates, which were obtained af-
serves as a substrate for the biosynthesis of the bile acids ter digestion with Alcalase, Esperase, Neutrase, Orientase
in the liver. Hence, the sequestration of the bile acids leads and Pronase and characterized by degrees of hydrolysis be-
to degradation of cholesterol, which therefore reduces the tween 24.7% and 36.3% and contained low molecular size
level of cholesterol in the blood (Anderson Siesel, 1990). peptides (under 1 kDa), have been shown to increase the
The in vitro hypocholesterolemic properties of rapeseed maximal cell density of Chinese Hamster Ovary (CHO)
proteins have been evaluated through the determination of C5 cells (Chabanon et al., 2008). Cell growth in the pres-
the bile acid-binding capacity. Yoshie-Stark, Wada, and ence of hydrolysates reached 120e150% of the reference


cells (grown in media without supplementation with the bonding. Ionic bonding is very strong, and thus the separa-
rapeseed hydrolysates) in serum-free medium, which con- tion of protein/phenolic complexes is extremely difficult. In
sisted of a simple basal medium supplemented with trans- this way, some studies have attempted to understand the
ferrin, insulin, albumin and trace elements. In addition to types of interactions between canola proteins and phenolic
the nutritional effect of the rapeseed protein hydrolysates, compounds and identify ways to effectively and economi-
which are rich in free amino acids, the presence of peptides cally remove these coloring materials. Xu and Diosady
that affect growth or survival, including anti-apoptotic ac- (2000) developed a technique for the quantitative character-
tivity, have been also suggested to explain the positive ization of canola proteinephenolic bonding in aqueous so-
growth effects of the rapeseed protein hydrolysates lutions. The proposed approach combined chemical
(Chabanon et al., 2008; Farges, Chenu, Marc, Goergen, treatments, which disrupted specific types of proteinephe-
2008). nolic bonds, with membrane separation to remove the re-
A fraction of Alcalase-hydrolyzed rapeseed proteins that leased phenolic compounds. It has been reported that up
was purified by ultrafiltration (3 and 1 kDa) and nanofiltra- to 50% of the extracted phenolic compounds formed com-
tion (500 Da), which produced a mixture of both large plexes with canola proteins by different mechanisms of in-
(500e5000 Da) and small peptides (500 Da), signifi- teraction, among which ionic bonding accounted for about
cantly stimulated the growth rates of CHO and other animal 30%. It is interesting that this kind of interaction is consid-
cells, including NS0, CHO K1 and Vero cells, and a maxi- ered to be the strongest among the interaction types. Xu and
mal cell density of 1.7Â was obtained by addition of 4 g/l Diosady (2000) concluded that the amount of phenolic
of hydrolysate. Moreover, the purified fraction reduced the compounds bound by canola proteins through hydrophobic
death rate of CHO cells, increased the secretion of g-inter- interactions, hydrogen bonding, and covalent bonding did
feron and accelerated cell adaptation to serum-free condi- not exceed 10% of the total extractable phenolic com-
tions (Farges-Haddani et al., 2006; Farges et al., 2008). pounds. A combination of chemical treatments and mem-
brane processes is one of the most promising ways to
Color of canola protein solutions remove the phenolic compounds (Tzeng, Diosady,
Like many plant materials, canola contains a consider- Rubin, 1990).
able quantity of phenolic compounds. Most phenolic com- According to the United States Patent 7678392 (Green,
pounds identified in canola are phenolic acids and Milanova, Segall, Xu, 2003), a process for the prepara-
condensed tannins, which are flavonoid-based polymeric tion of a canola protein isolate with improved color from
phenolic compounds. The major phenolic component in ca- canola meal was proposed. The process comprises the ex-
nola was reported to be sinapine, the choline ester of si- traction of the canola meal to solubilize canola proteins
napic acid. The overall concentration of these compounds in an aqueous solution at pH 5 to 6.8, the separation of
is not negligible; it is estimated to be about 1% (w/w) of the canola aqueous protein solution from the residual oil
the meal. Condensed tannins may cause astringency due seed meal, the concentration of the obtained canola protein
to their ability to precipitate proteins in the mouth. After while maintaining a constant ionic strength of the aqueous
oxidation, phenolic compounds induce the development canola protein solution by ultrafiltration, diafiltration of the
of dark colors in canola proteins. Phenolic compounds concentrated canola protein solution until no significant
are highly reactive molecules, and under alkaline condi- further quantities of phenols and color were present in the
tions, they can undergo enzymatic as well as non-enzymatic permeate, dilution of the diafiltered protein solution into
oxidation to form quinones, which can react with proteins water chilled to below 15 C to form discrete canola protein
and produce dark green or brown colors in canola protein micelles, the formation of an amorphous, sticky, gelatinous,
solutions (Leung, Fenton, Mueller, Clandinin, 1979; gluten-like canola protein micellar mass, and finally the re-
Xu Diosady, 2000). In most processes used to produce covery of the canola protein micellar mass (protein isolate)
canola proteins, the color of the isoelectrically precipitated with a protein content of at least 90% (w/w).
canola proteins cannot be washed or enhanced without sig-
nificant protein losses and increasing the overall process Undesirable compounds
cost. One of the limiting factors for the use of these proteins Phenolics are generally considered to be responsible for
in food applications is related to the presence of undesirable the dark color, undesirable flavour and lower nutritional
colors; thus, to produce canola protein concentrates and value of rapeseed products. Rapeseed/canola meal contains
isolates that can be used in food formulations, these color- free phenolic acids which constitute up to 24% of the total
ing compounds must be effectively and economically re- phenolic acids present in rapeseed/canola meal and flours.
moved. The interactions between phenolic compounds These free phenolic acids represent approximately 15% of
and canola proteins are complex (Rubino, Arntfield, the total phenolics present in rapeseed/canola meals
Nadon, Bernatsky, 1996). It has been established that (Krygier, Sosulski, Hogge, 1982). Rapeseed/canola pro-
these compounds in canola proteins interact through a vari- tein products contain different phenolics acids such as si-
ety of mechanisms in aqueous media, including hydrogen napic, p-hydroxybenzoic, vanillic, gentisic, protocatechuic,
bonding, covalent and hydrophobic interactions, and ionic syringic,p-coumaric, cis- and tran-ferulic, caffeic and


chlorogenic acids in the free form (Naczk, Amarowicz, Erucic acid in the oil may cause heart lesion in certain ex-
Shahidi, 1998). These phenolic acids are derivatives of ben- perimental animals. However, even if the new varieties are
zoic and cinnamic acids. It was found that sinapic acid is the significantly improved, they still contain too high levels of
predominant phenolic acid in rapeseed/canola cultivars. glucosinolates. Different approaches such as chemical
Phenolic acids are present in canola protein products in the modifications, microbial and physical treatments and their
free, esterified and bound forms. One of the limiting factors combinations have been used to reduce the content of glu-
of the use of canola meal residue and derivatives (protein cosinolates in meals or seeds to negligible levels. Recently,
concentrates and isolates) is that the content of phenolic the use of membrane filtration seems to be promising to re-
acids in these meals is up to five times higher than in soybean duce the glucosinolates content in canola protein isolates.
meals and the content of phenolic acids in rapeseed/canola Another limiting factor is due to the fact that rapeseed/ca-
flours is 10e30 times higher than in flours from other oleag- nola proteins contain up to 4% phytates (Naczk, Diosady,
inous seeds such as flaxseed. It has been reported that free Rubin, 1986). Phytates are responsible for the decrease in
and esterified phenolic acids are the principal contributors the bioavailability of divalent cations such as Ca, Mg, Zn,
to the undesirable taste of rapeseed/canola products. All Cu and Fe. This is a result complex formation (chelating ef-
the followings phenolics are found in rapessed/canola meals fect). Phytates are also known to inhibit the digestion of
and derivatives: protocatechuic, vanillic, syringic, gallic, starch. Because of this, a number of methods have been de-
p-hydroxybenzoic, p-coumaric, caffeic,ferulic, sinapic veloped to remove phytic acid from rapeseed products
acids. Of these phenolics, sinapic acids constitute 70e85% (Naczk et al., 1998). On the other hand, some recently pub-
of the total phenolic acids present (Naczk et al., 1998). On lished studies indicate that phytates, at low concentrations,
the other hand, the flavour of phenolic acids was described may possess antioxidative and anticarcinogenic effects
as sour, astringent, bitter and phenol-like. This taste is also (Rickard Thompson, 1997). Rapeseed meal contains up
found in canola meals and proteins. Condensed tannins are to 20e30% indigestible fibres on a dry basis. The rapeseed
also found in rapessed/canola meal residue and proteins ex- fibres are low-molecular-weight carbohydrates, polysaccha-
tracted from it. They are dimers, oligomers and polymers of rides, pectins, cellulose and lignin. Generally, they are com-
flavan-3-ols. The consecutive units of condensed tannins are plexed to proteins, polyphenols, glucosinolates and
linked through inter-flavanoid bonds between C-4 and C-8 or minerals. High levels of fibres limit the use of meal as
C-6 atoms. Condensed tannins upon acidic hydrolysis pro- food ingredient. Dehulling of rapeseed/canola has been pro-
duce anthocyanidins and therefore are also known as proan- posed but it is still not efficient and therefore dehulling is
thocyanidins. Rapeseed/canola meals may contain up to 3% not a standard practice in canola processing (Naczk et al.,
tannins (Clandinin Heard, 1968; Shahidi Naczk, 1989). 1998).
Proteins are macromolecules and may interact with flavour-
ing compounds such as phenolics. The character of these in- Food applications
teractions influences the flavour release and its perception. Canola proteins are characterized by interesting func-
Phenolic compounds may form soluble and insoluble com- tional properties that allow them to be used as ingredients
plexes with proteins. The phenol-protein complexes may in different food formulations. Native and partially hydro-
be stabilized by covalent bonds, ionic bonds, hydrogen bond- lyzed canola proteins have been extensively studied for po-
ing and/or hydrophobic interactions (Shahidi Naczk, tentials uses in the food industry to replace classical
1995). Studies on the complexations of polyphenols with ingredients, such as milk whey and egg yolk. This approach
proteins mainly concentrated on the evaluation of factors is mainly justified by economic considerations and possible
influencing these interactions and on the impact of formation whey/egg allergies in customers. In this context, an alkaline
of phenol-protein complexes on nutritive value of proteins. extract of canola meal was hydrolyzed using a protease to
The phenol-protein interactions are affected both by the obtain protein hydrolysates with 7% and 14% degrees of
size, conformation and charge density (zeta-potential) of hydrolysis (DH), respectively. The protein hydrolysates
the proteins and by the size, and flexibility of phenol mole- were used to replace up to 50% (w/w) of the egg yolk in
cule (Hagerman Butler, 1981; Naczk et al., 1998). a model mayonnaise preparation, and the effects on the
Even if the proximate composition, nutritive value and physicochemical properties of the end product were deter-
functional properties of rapeseed/canola meal and deriva- mined. It was found that unhydrolyzed canola proteins
tives (protein concentrates and isolates) are comparable to could only be substituted in mayonnaise for a maximum
soybean products, the use of rapeseed/canola protein prod- 15% (w/w) of the egg yolk without emulsion breakdown.
ucts as food ingredient is limited by the presence of unde- According to the authors, at 7% DH, the canola protein
sirable components such as glucosinolates, phytates, and could be used to substitute up to 20% (w/w) of the egg
fibres. The composition of rapeseed has been significantly yolk, while at 14% DH, the maximum level of substitution
improved by developing low glucosinolate and low erucic was up to 50% (w/w). However, some problems, including
acid rapeseed/canola cultivars. Glycosinolates upon hydro- the dark color of the canola protein solution, still need to be
lysis produce nitriles, hydroxynitrites, isothiocyanates and solved before the use of canola protein can be extended to
thiocyanates which are responsible for goitrogenic effects. food formulations. Aluko and McIntosh (2005) reported

Canola protein

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