Structure and chemistry of cereals

1. Cereal Chemistry and Bakery
products technology
FST 2263

2. Aim of the course:
•To provide the knowledge on physico-chemical
properties of cereal flours and their contribution
in attaining the specific properties of cereal based
products
•To
provide
the
knowledge
and
hands-on
experience on processing of different bakery
products.

3. At the end of the course student will be able to;
1. Describe the physico-chemical properties of cereal flour and
flour constituents
2. Evaluate the functionality of cereal flour constituents in flour
based products
3. Explain the principles of methods used in determining the
physicochemical properties of cereal flours and starches
4. Compare the techniques of processing of bakery products
5. Discuss the quality control practices applied in bakery
industry
6. Practice the preparation of basic bakery products

4. At the end of the lesson student will be able to;
• Identify structure & composition of cereal grains
• Compare the nutrient composition and physicochemical properties of different cereal flour
• Differentiate cereal starch according to structure
• Explain the specialty of different cereal starches

5. Structure & composition of cereal grains
Wheat
Barley
Rice
Maize (corn),
Oats

6. Cereals
• Belongs to gramineae (grass) family
• Seed is commonly called as grain/ caryopsis
• Main CHO source in many nations diet
• Each cereal has unique properties which make it
suitable for a variety of food products
• Cereals require different conditions to grow.
Ex: rice - tropical climates, oats – cold temperate

7. 1. Wheat
•Wheat (Triticum spp.) is a grass that is cultivated
temperate zone.
• The most important human food grain and ranks
second in total production as a cereal crop behind
maize; the third being rice
• Wheat grain is a staple food used to make flour
for breads; cookies, cakes, pasta, noodles.

8. Common Species of wheat :•Triticum aestivum – Common wheat
•T. monococcum
•T. vulgare
•T. dicoccum – has certain disease resistance qualities
•Triticum compactum – Two types; white & red
varieties
•T. durum/ Durum wheat/ Macaroni wheat – has a
hard, translucent, light colored endosperm which
makes it suitable as an ingredient for pasta

9. Common bread wheat can be categorized as:
• Hard / Soft varieties
• Spring / winter varieties
• White / red varieties
• Hard Red Spring — Hard, brownish, high protein wheat
used for bread and hard baked goods
- use to make bread Flour and high gluten flours
• Hard Red Winter — Hard, brownish, high protein wheat
used for bread, hard baked goods and as an adjunct in
other flours to increase protein in pastry flour
- use to prepare some brands of unbleached allpurpose flours

10. Soft Red Winter — Soft, low protein wheat used for cakes, pie
crusts, biscuits.
- use to make cake flour, pastry flour, and some selfrising flours
Hard White — Hard, light colored, opaque, chalky, medium
protein wheat planted in dry, temperate areas
- Used for bread and brewing.
Soft White — Soft, light colored, very low protein wheat grown
in temperate moist areas
- Used for pie crusts and pastry.
• Hard wheats are harder to process and red wheats may need
bleaching. So, soft and white wheats usually have higher
prices than hard and red wheats on the commodities market.

11. • Raw wheat seed - food ingredient called whole
wheat
• can be powdered into flour, germinated and dried
creating malt, crushed and de-branned into
cracked wheat, parboiled (or steamed), dried, or
processed into semolina, pasta
• These processed wheat are a major ingredient in
such foods as bread, breakfast cereals, crackers,
biscuits, pancakes & cakes

12. Structure of the wheat grain:
• Wheat grains -
generally oval shaped ( range
from spherical to long, narrow and flattened
shapes)
• 5 and 9mm in length, weighs between 35 and
50mg
• Wheat grain has a crease down one side where it
was originally connected to the wheat flower.

13. Wheat grain, showing different sides and cross section to
illustrate the depth of the crease

14. Pericarp
Outer pericarp
Inner pericarp
Grain
Seed
Seed coat (Testa)
Endosperm
Aleurone layer
Germ

15. Pericarp
• outer most cover
• outer pericarp consists of 3 layers
• epidermis
• hypodermis
• Inner thin walled cell
• Inner pericarp consists of
• Intermediate cells
• cross cell
•Tube cell

16. Seed coat
• firmly attached to the tube cells
• if these layer carries pigments, kernel is colorful
Aleurone layer
• Outer most layer of the endosperm which contains
vitamin B

17. Structure of the Wheat grain

19. The three main parts are:
1. Bran
• outer layers of the wheat grain; removed during
milling
• About 14% of the wheat kernel
• The outer coating or 'shell' of the wheat kernel is
made up of several layers
•These layers protect the main part of the kernel
• Bran is rich in B vitamins and minerals
• Wholemeal flour contains all the naturally
occurring bran.

20. 2. Endosperm
• main part of the wheat kernel or name given to
the interior of a wheat kernel
• represents about 80% of the kernel weight
• The endosperm, once it has been ground down
to a powder, is wheat flour
• It is from this part that white flour is milled. The
endosperm is rich in energy-yielding carbohydrate
and important protein.

21. 3. Germ (Embryo)
• part of the grain which would sprout if it was planted
as a seed
• packed with nutrients and protein with which to
nourish a new plant
• During milling the germ is usually separated from the
rest of the wheat grain ( fat content limits the shelf life
of the flour)
• The germ lies at one end of the grain and represents
only 2% of the kernel
• rich source of B vitamins, oil, vitamin E and natural
plant fat.

22. Chemistry of wheat grain (Per 100 g)

23. Rice (Oryza sativa)
•most important cereal crop in developing world
• staple food of over half the world's population
 production is only slightly below that of wheat
 90% is grown in southern & eastern Asian
Grain structure
 consists of an outer protective covering, the hull,
and the rice caryopsis or fruit
Brown rice consists of the outer layers of pericarp,
seed-coat and nucellus; the germ or embryo; and
the endosperm

25. • Endosperm consists of the subaleurone layer and
starchy endosperm.
• The aleurone layer encloses the embryo
• The hull constitutes about 20 % of the rough rice
weight.
•The distribution of brown rice weight:
• Pericarp
1-2%
• Aleurone, nucellus, seed-coat
4 - 6%
• Germ
1 %
• Scutellum
2%
•Endosperm
90 - 91 %

26. • The endosperm cells : thin-walled and packed with
starch granules
• The two outermost cell layers are rich in proteins
and lipids
• have smaller amyloplasts & starch granules than
the inner endosperm.
• starch granules are polyhedral and mainly 3 - 9 µm
in size
• Protein occurs mainly in the form of spherical
protein bodies

27. Chemical composition of rice grain
Hulled rice
Rice bran
Water
10 – 12%
Water
Protein
5 – 9%
Protein 10.6 – 14.8%
Fat
0.6 – 2.6%
CHO
73 – 90%
Fiber
0.2 – 1%
Ash
0.8 - 2%
Fat
Fiber
Ash
8.9 – 12.5%
10.6 – 22.4%
9.6 – 11.1%
9.3 – 15%

28. A. Oats (Avena sativa);
(Triticum aestivum);
D. Rye (Secale cereale).
B. Barley (Hordeum vulgare); C. Bread Wheat

29. Rye
Chemical & physical characteristics
-The rye kernel is a caryopsis.
- Caryopsis is a small dry, indehiscent, one seeded
fruit.
-6 – 8 mm in length & 2 – 3 mm in width.
-The color is normally grayish yellow
-The seed consists of an embryo attach through a
scutellum to the endosperm & Aleurone layer

30. -The pericarp or fruit coat surrounds the whole seed
& adhere closely to it.
-A crease or furrow extends the full length of the
grain on the ventral side
-The nutritional quality of rye protein - superior to that
of other cereals because of its better balance of EAA.
-Its protein efficiency ratio seems to be higher due to;
- the greater amount of lysine present in the
water soluble proteins & the higher proportion of
globulin & albumin

31. -Rye lipids differ from those of most other cereals
by having a slightly greater proportion of the highly
unsaturated linolenic acid.
-Therefore susceptible to oxidation. cause rancidity
-Starch granules have a mean particle diameter
greater than those of other cereals
-shape
lenticular shape
spherical shape

32. - 8% pentosans in rye (in wheat is 3%)
- rye bread has large pores & moisture than wheat
bread
-Rye has few micronutrients;
•Thiamine
•Nicotinic acid
•Riboflavin
•Pyridoxin
•Pantothenic acid
•Tocopherol

33. Oats(Avenea sativa)
-grown in cooler & moisture regions of the
temperate zones
-varieties
o red oats – heat tolerant
•southern US, South America, Australia
• Winter oats – planted in the late fall, latitude of 20
- 400
• Spring oats – planted when the threat of frost is
minimum

34. - used to prepare cakes, biscuits, & breakfast
cereals
- The physical structure of the oat grain is similar to
that of kernel of wheat & barley
- The 3 major divisions
- Bran
- Endosperm
- Germ
- The oat germ is larger & narrower than the germ of
wheat
- Compared to other cereals oat grains are
characterized by low CHO contents & higher protein
& fat content

35. Barley
Genus: Hardeum
Most of the cultivated barley classified in to two groups
1. H. vulgare – six rowed barley
2. H. distictum – two rowed barley
Structure of Barley kernel
The caryopsis is composed of
 Pericarp
 Integuments
 Starchy endosperm
 Germ

36. -The outer layer of endosperm is made out of
aleurone cells
-In blue barley, blue color is due to color given by
the anthocynin pigments in alkaline aleurone cells
Composition of barley
Protein
12%
CHO
70%
Mineral
2%

37. -Low in EAA esp lysine & Methionine
-Have more lysine than corn
-Contains larger amount of vitamin compared to corn
-Barley granules
Large granules(A)
Small granules(B)
Large granules(A) - contain high amylopectin
-have lower gelatinization tem
small granules(B) -contain low amylopectin
-have higher gelatinization tem

38. There are two major groups of protein
1. Glutelins
& Prolamins
2. Albumins & globulins
Uses
1. source of malt in manufacture of alcohols,
wisky, beer
2. use as a flavoring agent in breakfast cereals,
malted milk, infant foods, medicinal syrups

39. Sorghum (Sorghum vulgare )
-Staple food in drier part of tropical Africa, china,
India
-Native home is Africa
-The grains are differently colored – Yellow, Red,
or Brown
Composition
Fat
3%
CHO
70%
Fiber
12%

40. Millets
-Common term used to large number of cultivated
grasses with very small seeds
-Used as forage & as a food for both man &
domestic animals
-More important in the East than West
-Generally known as poor man’s cereal

41. 1. Fortail millets ( Setaria italica)
- Grown in Japan, China, India – grains are boiled
eaten
- In North America - mainly used as a forage crop
2. Proso millet (Panicum miliaceum) – Contains 10 %
proteins,
4 % Fat
- A palatable bread can be made from these
3.Finger millet (Eleusine coracana)
- Grown mainly in the tropics
- Most important cereal crop in chena in Sri
Lanka

42. Maize (Zea mays)
-Originated in low land of tropical South America
-Leading producers : USA, China, Russia, India,
Italy
Kind of maize:
Cultivars are divided in to groups, according to
structure of grains
1.Pod corn — Zea mays var. tunicata
-Most primitive form
-not grown commercially

43. 2.
Popcorn — Zea mays var. everta
-Grains small with a little soft starch at the center
-When heating cause the grains to pop
3.
Flint corn — Zea mays var. indurate
-Grains with hard endosperm
-A little, soft starch in the center
-Well adopted to poultry feed
4.
Dent corn — Zea mays var. indentata
-Principle maize of US & North mexico
-White starch shrinks on drying to produce a characteristic dent

44. 5.
Sweetcorn — Zea mays var. saccharata
- Grain consist a glossy sweetish endosperm
- Cobs are picked immature for boiling as corn on the
- Also use as a vegetable by canning or freezing
6.
Flour corn — Zea mays var. amylacea
- Endosperm consists with soft starch
7.
Waxy corn — Zea mays var. ceratina
- Starch is waxy & composed of entirely of amylopectin
cobs