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PHYSICO-CHEMICALAND SENSORY EVALUATIONOF RICE-SOYAYOGHURT
A Thesis
Submittedto the College ofAppliedFoodScience and Tourism
In partial fulfillmentofthe requirementsforthe degree of
Masters of Science
By
Ezieke Jennifer
B.Sc., Michael Okpara UniversityofAgriculture Umudike,2012
Mouau/PG/M.Sc/13/3513

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INTRODUCTION
1.1 IMPORTANCE OF MILK AND MILK PRODUCTS IN DIET
Milk is the secreted fluids from mammary glands of the female mammals. It contains all necessary
nutrients for the first phase of the life of every mammal’s offspring. Throughout the world,
livestocks are kept in order to collect their milk and milk is part of the diet of humans around the
world. The term “milk” is synonymous with cow’s milk as cow’s milk constitute most of the world’s
milkproduction (Belitzetal.,2004).
Fluid milk is not only nature’s food for new born infant, but also a source for a whole range of dairy
products consumed by mankind. Fluid milk is about 87% water and 13% solids. The fat portion of the
milk contains fat- soluble vitamins. The solids other than fat include proteins, carbohydrate, water-
soluble vitamins and minerals. Milk products contain high quality proteins. The whey protein
constitutes about 18% of the protein content of the milk. Casein, a protein found in milk contains
essential amino acids, calcium, phosphorus, magnesium, and potassium. The calcium found in milk is
readily absorbed by the body. Vitamins D plays a role in calcium absorption and utilization. Milk is
also a significant source of riboflavin ( vitamin B2), which helps promote healthy skin and eyes (Dairy
Facts, 2003). Dairy products such as yogurt, cheeses, and ice-creams contain nutrients such as
proteins,vitaminsandminerals.
1.2 FERMENTED MILK PRODUCTS
The introduction of fermented milk products such as cheeses and yogurts in to the diet of man is
thought to date back to the dawn of civilization (McKinley, 2005). Consumption of fermented milk
products is associated with several types of human health benefits partly because of their content of
lacticacid bacteria.
1.3 YOGURT
Yogurt is a product of the lactic acid fermentation of milk by addition of a starter culture containing
Streptococcus thermophilus and Lactobacillus delbrueckii ssp. Bulgaricus. In some countries, less
traditional microorganisms, such as Lactobacillus helveticus and Lactobacillus delbrueckii spp are
used. Lactis are sometimes mixed with the starter culture (McKinley, 2005, Hui, 1992). Although
fermented milk products such as yogurts were originally developed simply as a means of preserving
the nutrients in milk, it was soon discovered that, by fermenting with different microorganisms, an
opportunity existed to develop a wide range of products with different flavors, textures,
consistenciesandmore recently,healthattributes.
The yogurt production probably exceeds 20 million tons per year worldwide (Lucy and Singh, 1998)
and yogurt is traditionally produced from whole milk (Tamme and Robinson, 2007). The consumers
inmost westerncountriesare becomingincreasinglyinterestedinlow fat dairyproducts,e.g. skim

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milkstirredyogurt(Valli andTraill,2004: Sandoval- Castillaet.al., 2004).
Yogurt was introduced to the Nigerian diet during the 1990. By the 1980s, it had become the
product for dieters, and the lunch of choice for young women. The use of yogurt as a calcium source
has made it one of the most rapidly growing dairy products and presently it is more than just
calcium source. Yogurt, kefir, and similar fermented milk products are becoming major
neutraceuticals aimed at treating a variety of disease conditions (Katz, 2001). The nutritional profile
of yogurt has a similar composition to the milk from which it is made but will vary somewhat if fruit,
cereal or other components are added. Yogurt may be spoonable or drinkable, and may be
considered dietary supplements for infant consumption. So they cross the line between dietary
supplements,medical foods,andconventional foods(Katz,F.2001).
1.4 VEGETABLE MILK
In view of the continued diary milk shortage or absence in the developing countries, therefore had
led to the production of milk substitute from vegetable milk. According to Harkins and Sarret(1967),
development of milk substitute extracted from legumes serves as an alternative way of producing
an acceptable nutritious food based on vegetable is increasing. Vegetable milk (analogue milk or
plant milk) is a general term for any non-diary cream analogue that is derived from a plant source
(http://www.en.wikipedia/milk analogue, 2013). No formal or legal definitions for vegetable milk
exits in most countries. The most common varieties are soy cream, oat cream, but there are also
other varieties available which are rice or nut based. There are variety of reasons for consuming
vegetable milk, including severe diseases like PKU, making digestion of animal proteins(especially
casein) found in dairy milk allergic (approximately 3% of people are allergic)
(http://www.en.wikpedia/wiki/plantcream).
Vegetable milks can be used for babies in communities where babies are not given dairy milk for
ethical reasons and galactosemia (Obizoba and Egbuna,1992). Attention and more research are still
beingdesignedtoimprove the qualitythe qualityof soymilk(Sun-youngetal.;2000).
1.4.1 RICE MILK
Rice is the seed of the grass species Oryza sativa (Asian rice) or Oryza glaberrima (African rice) is
widely consumed staple food for a large part of world’s human population. Rice milk is a cereal
grain milk made from rice. It is mostly made from brown rice and commonly unsweetened
(http://www.en.wikipedia.org/wiki/rice). The sweetness in most rice milk varieties is generated by a
natural enzymatic process, cleaving the carbohydrates into sugars, especially glucose, similar to the
Japanese amazake (http://www.bnet.com/ricemilk). Some milks may nevertheless be sweetened
withsugar cane syrupor othersugars.
Compared to cow’s milk, rice milk contains more carbohydrates, but does not contain significant
amounts of calcium, vitamin B12, vitamin B3, and iron. Rice milk is often consumed by people who
are lactose intolerant, allergic to soy or have PKU. It is also used as diary substitute for vegeterans,
and rice milkdoesnotcontaincholesterol orlactose (http://www.en.wikipedia/wiki/ricemilk).

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1.4.2 SOY MILK
Soybean (Glycine max) is a legume of an exceptionally high protein content ranging between
38% and 42% with lysine constituting a substantial proportion (Nwanebu, 1994 cited in Egbo,
2012: Lawson, 2004). Soy bean as a plant protein is cheaper and could serve as an alternative to
cow milk. It contains up to 40% protein compared with 1.0% to 5.6% protein content of most
animal milk(Farinde etal.,2008).
Soymilk is a fine emulsion of soy bean flour or water extract of wet ground soybean. Among the
sources of vegetable milk, soy bean has received high research attention and more research is
still designed to improve the quality of soymilk (Sun-young et.al., 2000). Though the soya beans
is classified among the leguminous plant, it differs from other legumes in containing far more
proteinsandfatsthan ordinarypeasandbeans.
Scientific studies have emphasized the fact that the soybean contains vitamins in substantial
quantities and is a valuable source of B-complex vitamins. Soybeans protein contains essential
amino acids and is therefore a complete protein which satisfies the human requirement for
proteinmetabolism (Ref).

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1.5 PROBLEM STATEMENT
The scarcity of milk supply in developing countries perhaps led to the development of alternative
milk from vegetable sources (Singh and Bains, 1988). However, prior to the development of such
vegetable milk like soymilk which serve as a less expensive substitute for diary milk, direct milk
consumption as a beverage was not common in Nigeria (Iwuoha and Umunnakwe, 1997; Onweluzo
and Owo, 2005). According to Harkins and Saret (1997), development of milk substitutes extracted
from legumes serves as an alternative way of producing an acceptable nutritious food based on
vegetables.
Dairy milk which contains high quality protein and other nutrients is essential for the well-being of
an individual, for some reasons not consumed by all, due to health conditions such as inability to
digest milk sugar-lactose, milk allergy, and PKU. Casein, a protein found only in milk, contains all of
the essential amino acids and accounts for 82% of the total proteinsin milk are indigestible by some
individuals.
In Nigeria, rice is a vital staple food consumed by many people. Rice (Oryza spp) is the most
important food crop in the world, being the staple food for more than half of the world’s
population, predominantly in Asia and Africa where more than 90% of the world’s rice is grown and
consumed. It is a very versatile crop and there are many varieties of rice adapted to various
environmentandcultivationpractices(Luc et al., 2010).
1.6 OBJECTIVE OF STUDY
The Objectivesof the researchisdesignto achieve the following:
i. To evaluate the nutritionalpropertyof rice- soymilkyogurt.
ii. To augmentnutrientdeficiencyinrice milk
iii. To evaluate itsgeneral acceptability.

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1.7 JUSTIFICATION
Rice milk contains twice as much carbohydrate as cow’s milk with high level of antioxidant,
selenium and magnesium, deficient in protein. However, due to its low protein content will be
augmented with soy bean which contains same amount and quality protein as that in cow’s
milk.

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MATERIALS AND METHOD
The raw-materials which are Soybean (Glycine max) and Rice (Oryza sativa) will be purchased
frommile 3 market,Port Harcourt, RiverState.
2.2 PREPARATION OF RICEMILK
The rice (200g) will be washed thoroughly and kept in a pot. Two (2) litres of water will be added
and the whole content placed on heating mantle to boil. A low temperature (??? ) with
minimum time of 3hourswill be applied to generate a soupy rice pudding. The boiled rice will be
blended with 400ml of water to obtain a smooth content, and the mixture strained to obtained
the rice milk.
2.3 PREPARATION OF SOYMILK
The soybean milk will be prepared using traditional Chinese method, 200g of soya bean will be
soaked in 2 litres of water for 28 hours and then dehulled and rinsed with tap water. The beans
will be wet milled (1:4 liters of water). The soymilkwill be obtained by passing the slurry through
0.4mm screenfollowedby pasteurizationat68°C for 30mm.
2.4 PREPARATION AND INNOCULATIONRICE-SOYAMILK
Rice-Soya yogurt will be prepared by mixing, rice milk and soy milk in ratios 25:75, 50:50, 75:25
respectively representing treatment B, C , and D while A will be commercial yogurt. The various
mixturesof rice milkandsoymilkwill be heated atbetween85°Cto 95°C for 3minutes.
The milk will be rapidly cooled to 40°C and then inoculated with 2% mixed culture of
Streptococcus thermophillus and Lactobacillus bulgaricus at ratio 1:1 and the mixture will be
thoroughly mixed and incubated between 43°C to 45°C for 8 to 12hours till the curd is formed
(Belewu,2006).
Rice
Soybean
ssseeseesee

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Screening
Washing
Soakin tap waterfor28hrs
Cookeduntil very Soft
Blending(200gRice+400ml Water) Draining
Filterusingsieve
Decoatand rinse twice withtapwater
Grindat 27°C- 30°C
Sieve with0.04 mm sieve
Pasteurize at68°C for 30 min
Soymilk
Blends at different ratios
(100%, 75:25, 50:50, 25:75)
Inoculation using the bacteria starter culture and incubate for 8:12hrs
Rice-Soya Milk
Rice Milk

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2.5 PHYSIOCHEMICALANALYSIS
2.5.1 PROXIMATE ANALYSIS
The chemical composition,(moisture content, Ash, Protein, Carbohydrate, lipid, fiber) will be
determinedaccording tothe methodof A.O.A.C.(1990) and Onwuka(1995)
.
2.5.2 Ph MEASUREMENT
The pH will be determinedatroom temperature (27°C) usingdigital pHmeter.
2.5.3 TITRATABLE ACIDITY
The titratable acidity will be measured by titrating 15ml of different yogurt treatments with
0.1M sodium hydroxide until the substances reached a pH value 8.2, corresponding to the
end point of the phenolphthalein. When this value is recorded, the spent NaOH volume will
be recordedand the acidpercentage of the substance wascalculatedusingthe formula:
Titratable acidity(T):Titre value x Mx100
Volume of sample x 1000
Where,M= Molar Concentrationof NAOH
2.5.4 TOTAL SOLIDS
The weight of the residue obtained from moisture content analysis will be expressed as
percentage total solidsusingthe formulabelow.
Total solids(%) =(weightof dish+ dryyoghurt) - (weightof dish) x 100
Weightsample
2.5.5 SOLIDS-NOT-FAT
Solids-not-fat will be determined by conducting total solids and fat analyses. Percent fat will
be subtractedfrompercenttotal solidstoobtainpercentsolids-not-fat.
2.5.6 ENERGY VALUE
Energyvalue will be estimatedusingthe methodof CarpenterandClegg(1956).

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2.5.7 MINERAL ELEMENTS
The major and minor mineral elements will be determined using Atomic absorption
emission spectrophotometer(ASS)
2.6.7 VISCOSITY
The viscosityof the treatmentwill be evaluatedusingthe method of Onwuka(2005).
SENSORY EVALUATION
A twenty-man untrained panelist will be used to evaluate the organoleptic characteristics (taste, flavor,
constituency, colour, appearance, and general acceptability) of all samples and control using nine point
hedonicscale rangingwhere 1=dislike extremelyand9=like extremely (Onwuka,2005).
`

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REFERENCE
A.O.A.C (1990), Association of official Analytical chemists. Official methods of Analysis.
15th
edition.WashingtonD.C
Belewu, M.A (2006), A Functional Approach To Diary Science and Technology. Adiek
Publisher,Ilorin,Nigeria.
Belitz, H.D., Grosch, N. and, Schieberle,P., (2004), Food chemistry, 3rd
edition, Springer
Verlag,BerlinHeidelberg,Germany.
Carpenter, K.J. and Cleggs. K.M. (1956). The metabolizable energy of poultry feeding
stuffsinrelationtotheirchemical composition. J.Sc. FoodandAgric.7:45-51.
Diary Facts (2003) Edition, Nutrition information, 13, International Dairy foods
AssociationWashington,D.C,U.S.A.
Egbo, (2012)
Farinde, and (2008)
Harkins, R.W. and Sarret, H.P. (1967). Methods of comparing protein quality of
soyabeaninfantformulasinrat.J.Nutr.,91: 213-216.
Harkin,R.W. and Saret,H;P; (1997)
Hui, (1992)
http://www.bnet.com/ricemilk
http://www.en.wikipedia.org/wiki/rice
http://www.en.wikipedia/milk
http://www.en.wikipedia/wiki/ricemilk
Iwuoha, C.I. and K.E. Umunnakwe, K. E. (1997). Chemical physical and sensory
characteristics of soymilk as affected by processing method, temperature and duration
of storage.FoodChemistry 22:89-94

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Katz, F.,(2001). Active cultures and function of yogurt and other foods. Food Technology
55(3):46-49.
Lawson,……(2004)
Luc, and (2010)
Lucey, J.A. and Singh, H. (1998) formation and physical properties of acid milk gels: a
review.InFoodResearchInternational,Vol .30,ElsevierLtd.,UnitedKingdom.
McKinley, M. C. (2005). The nutrition and health benefits of yoghurt. International
Journal of Dairy Technology58(1):1-12
Nwanebu, (1994).
Obizoba, I.C. and Egbuna, H.I. (1992). Effect of germination and fermentation on the
nutritional quality of bambara nut. (Voandzei subterranean Thourars) and its product
(milk).PlantFoodsforHum.Nutr.,42:13-23.
Onweluzo, J.C. and Owo, O.S. (2005). Stabilization potential of water solube
polysaccharide from two indigenous legumes (Detarium microcarpum and Mucuna
flagellipies) in vegetable milk: Effects on selected quality characteristics. J. Home Econ.
Res.,6: 39-44.
Onwuka,G. I.(1995).
Onwuka, G. I. (2005)
Sandoval- Castilla, O., Lobato- Calleros, C.; Aguirre- Mandujano, E. and Vernon-Carter, E.J.
(2004) Microstructure and texture of yopgurt as influenced by fat replacers, In International
DairyJournal Vol.14,ElsevierLtd.,UnitedKingdom.
Singh, and Bains, (1988)
Sun-Young, P., Marsh, K.S. Jenny, Y.S. and Yon, S.E. (2000). A study on a processing
method to improve soymilk quality. Proceedings of Pre-Congress internet Conference,
May 8, Dec 31., PP: 31-32.
Tamme, A.Y. and Robinson, R.K., (2007). Yoghurt Science and Technology, 3.e.d.
Woodhead PublishingLtd.UnitedStates.

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Valli, C. and Traill, W.B.(2004). Culture and food: a model of yogurt consumption in the
EU, InFood QualityandPreference,Vol.16,ElsievierLtd.,UnitedKingdom.
My Observations:
I have triedto edityoursubmission butyouneedtonote the followingobservations:-
1. You have not shownhow youintend toachieve objectives1and 2.
2. In preparing your soy milk and rice milk, you must give credit to the source of
your methodologies unless they are your original methods. You need to do so
for mineral analysis and titratable acidity, etc. There is a place that I have
indicated that you provide references to back-up your statement where several
studieshave shownthat…….
3. There is need for you to clearly state how you intend to heat your milk mixtures and
inwhat system.
4. Do you have rice-soy milk after inoculating with bacteria culture and incubating for
8-12 hours?
5. There isno vitamindeterminationof youryogurtsamples.
6. Do youhave fiberinmilkandmilkproducts?
7. Whose method will youuse toevaluate solid-not-fat?
8. Use of energyvalue byCarpenterandClegg(1956).
9. Prof.M.O. Iwe’stextonSensoryEvaluationisabetterreferencethanOnwuka’s.
10. Unfortunately, you have failed to follow the approved Harvard system of
referencing. I have tried to make corrections and identified some references you
citedbutnot referenced.
11. Above all, I am not sure the quantum of work you set out to do will be enough for
an M.Sc Thesis. At least, you should increase both your sample size and analyses to
be performed.