Topic 4

Question 1

What is the chemical composition of cereal grains

Answer 1

Carbohydrates are 83% of wheat barley maize sorghum rice millet and 79% of oats
Protein is 9 to 16%
Lipids range from 0.9% to 9%
Mineral content is generally below 3% with the exception of rice which contains 7%

Question 2

Name the two parts of carbohydrates in cereals

Answer 2

One create father is the portion of carbohydrates that is insoluble in the dilute acids and alkalies
Soluble carbohydrates are calculated as the total dry matter of the grain less crude fibre nitrogenous substances lipids and minerals
Soluble carbohydrates consist of starch and sugars
Crude fibre include cellulose hemicellulose and pentosans

Question 3

Describe starches in cereal grains

Answer 3

Starch accounts for 64% of wheat grain on a dry matter basis
The two types of starch are amylose and amylopectin
Amylose is a linear polymer in which glucose residues linked by an alpha 1-4 bonds. Has a helical structure in solution, stains blue, common cereal starch = 25 to 27% amylose
Amylopectin: branched alpha 1 to 4 bonds doesn’t form a helix. Starches from rice and sorghum are almost entirely amylopectin.

Question 4

Explain starch gelatinisation

Answer 4

Gelatinisation is when a starch slurry is heated to 60°, water absorption increases greatly, swelling becomes irreversible, viscosity of the suspension increases dramatically.
Starch granules are not soluble in cold water, swelling is reversible.

Question 5

Stages of starch gelatinisation

Answer 5

One. swelling phase, the viscosity starts to increase rapidly at a certain temperature. This temperature is known as the pasting temperature
Two. Peak viscosity, discuss viscosity.
Three. Breakdown viscosity, viscosity to decreases gradually to lowest point.
Four. Set back, upon calling the viscosity increases again

Question 6

Retrogradation of starch

Answer 6

Crystals form at junction zones of network of amylose molecules in a starch gel and gel goes rigid. A return of the starch from a hydrated, dispersed, amorphous state to an insoluble, aggregated, or crystalline condition

Question 7

Protein in cereal grains

Answer 7

About 70% of the protein is located within the endosperm
Types of protein
Albumin, 2.5%, Soluble
globulin, about 5%, Soluble
proteose, about 2.5%
prolamin, 40% to 50%, Insoluble, Major component of gluten
glutelin, 40% 50%, Insoluble, Major component of gluten

Question 8

Amino acid composition in cereal grains

Answer 8

18 different amino acid’s. Amino acid composition is characterised by a high content of glutamic acid and proline and a low level of lysine

Question 9

Lipid content in cereal grains

Answer 9

Oh it’s have the highest lipid content, 5 to 10% with an average of about 7%.
Wheat and sorghum contain 2 to 3% of fat.
Below 2% for rice and barley
Deterioration – lipid hydrolysis (unpleasant flavour), lipid oxidation (rancid odours)

Question 10

Minerals in cereal grains

Answer 10

Most minerals found in cereals are phosphate and sulphate salts of potassium, magnesium, and calcium. Iron, manganese and zinc are present.

Question 11

The objectives of flour milling

Answer 11

To separate the endosperm from the germ and bran
To grind the separated and endosperm into a fine powder of flour
To extract maximum quantity of flour possible from the wheat grain

Question 12

The Objective of cleaning of wheat

Answer 12

Objective – remove impurities, known as dockings or screenings, plant matter, animal matter, microbial contamination is, minerals, other

Question 13

The washing of wheat

Answer 13

Immersed in water, transferred to centrifugal machine, agitated, separated from water, gains about 3% moisture.

Question 14

Removal of particle matters

Answer 14

Separation by size and shape
Separation by terminal velocity ( aspiration)
Separation by specific gravity
Separation by electromagnetic properties

Question 15

The objectives of conditioning of wheat

Answer 15

Overall, to improve the physical state of the grain for milling
To toughen the wheat bran
To improve the separability of the bran from the endosperm
To soften the endosperm

Question 16

Methods of conditioning wheat

Answer 16

Blending of wheat, Damp and dry wheats are blended together to reach moisture equilibrium.
Cold conditioning, cold water is added.
Warm conditioning, water is added, rate of moisture diffusion is determined by the temperature of the grain
Hot conditioning, temperature is raised to about 60°, duration is shorter
Steam conditioning, steam is in direct contact with the grains they are heated and dampened at the same time

Question 17

The objectives of flour milling

Answer 17

To separate the endosperm from the bran and germ

To reduce the separated endosperm into fine flour

Question 18

The four basic processing systems of a flour Mill

Answer 18

Breaking, grinding – A series of roller mills which open up and fragment the wheat grain
grading, sieving – break stock is fed into sieves. Large particles of a cold scalp.
purifying- middlings sent here
reducing systems- endosperm fraction is sent here to be reduced to flour.

Question 19

Flour extraction rate and flour yield

Answer 19

Terms used as indices of the efficiency of the milling process
The flour extraction rate is defined as the proportion of wheat recovered as flour, expressed as a percentage. The higher the extraction rate, the more efficient the milling process.
Flower you is defined as the amount of weight required to yield a given amount. The higher the flour yield, the lower the milling efficiency

Question 20

The extraction of gluten from wheat flour

Answer 20

The Martin process – dough is kneaded under running water
The batter process - A large amount of water is added, gluten globules separated by screening.
The alkaline process – flour is suspended in an alkaline solution. Starch is removed by centrifugation. Non vital gluten obtained.

Question 21

The classification of wheat

Answer 21

The texture or hardness of the endosperm – Performance of weight during milling. Defined as the resistance to crushing of individual kernels and the pattern of endosperm rupture in the milling process.
The protein content of the wheat – Determines quality of flour and suitability for various purposes.

Question 22

How hardness of wheat influences it’s milling performance

Answer 22

Hard wheats yield course, gritty flour with particles regular in size, free-flowing, easy to sift. Endosperm breaks away from the bran easily and cleanly.
Soft wheat produce a very fine flour with irregular particles. Tends to fragment. Lower levels of damaged starch.

Question 23

Strong and weak wheats

Answer 23

Strong wheat yields flour that produces bread with a large loaf volume, good texture, good keeping quality. Strong wheat has a high protein content.
Flours from weak wheats are not suitable for breadmaking but ideal for biscuits cookies and cakes.

Question 24

Parameters and tests for grading wheat quality

Answer 24

Test weight measures the density of wheat and provides a good indication of flour yield.
Moisture content is inversely related to the amount of dry matter in wheat.
Kernel weight is a function of kernel size and density.
Damaged kernels yield less flour than intact ones, may carry contaminants.
Impurities

Question 25

Flower improvement by bleaching

Answer 25

Yellow pigments – carotenoids, hydroxylated xanthophylls, esters of lutein, flavonoids. Usually oxidised to colourless compounds in oxygen.
Bleaching agents – benzoyl peroxide, acetone peroxide, chlorine dioxide, chlorine, soy bean lipoxygenase.

Question 26

Flour maturation and improvers

Answer 26

Storage improves breadmaking qualities. It is facilitated by the addition of certain chemicals.
Potassium bromate, L –ascorbic acid, cysteine, azodicarbonamide.

Question 27

Grading of flour

Answer 27

Small particles, 0 to 17, have a high protein content about 25%.
Medium particles, 17 to 40, consist mainly of starch granules, low in protein, About 5%.
Large particles, 40 to 80, have about 10% protein.

Question 28

Flower for special purposes.

Answer 28

Bread flour, protein content and wheat flour in the range of 8 to 18%.
Biscuit flour, low protein content of wheat, about 5 to 8%, soft wheat.
Cake flour, stability of cake is determined largely by presence of uniformly swollen starch granules, certain soft wheat types low to medium strength.
Self raising flour, flower blended with chemical leavening agents.
Plain flour

Question 29

Flour quality and testing

Answer 29

Purposes – for information about general quality such as moisture content, degree of freedom from contaminants. To obtain information about the nature of flour, protein content, damaged starch, etc.
Tests – Moisture content, protein content, sedimentation test for protein quality, alpha amylase activity, rheological properties and physical dough testing (brabender farinograph, brabender extensograph, chopping alveograph).

Question 30

The three events of bread making process

Answer 30

The hydration of flour proteins when mixed with water with the consequent formation of a gluten network.
The incorporation of carbon dioxide, produced by yeast formation, into gluten.
The coagulation of protein and gelatinisation of starch during oven heating.

Question 31

Ingredients used in bread

Answer 31

Wheat flour – wheat proteins and water form a Viscoelastic network during mixing, network aerated by carbon dioxide, expands and forms porous crumb during heating, hydrated starch gelatinises.
Water – facilitates the mixing of bread ingredients, hydrates flour proteins to form gluten, hydrates flour starch, forms a water phase in the dough, which dissolves the soluble solids such as sugars salts soluble proteins, etc, making them accessible to yeast.
Yeast- saccharomyces cerevisiae, aerates dough by carbon dioxide production through aerobic fermentation of glucose and fructose, contributes to flavour through release of secondary products of metabolism, including alcohol, acids, carbonyl and esters, contains invertase: hydrolyse is sucrose to glucose and fructose.
Salt – primarily for flavour, 1 to 1.3% of bread weight, retards growth of yeast.

Question 32

Improving ingredients in bread (additives)

Answer 32

Emulsifiers – increased dough stability and gas retention, improve loaf volume, improve the performance of weaker flour so that they can be used to make bread with acceptable quality, improve the dough stability gas retention and volume in wholemeal mixed grain and high-fibre bread, improve from softness, retard bread staling.
Common emulsifiers - glyceryl monostearate, lecithin, diacetylmorphine tartaric acid esters of monoglycerides.
Fats – increase crumb softness.
Milk powder – improve crust colour due to protein and sugar reaction, increases nutritional value.
Soy flour – improves crumb colour and nutritional value, emulsifying properties from lecithin, enzyme like lipoxygenase catalyses reaction between molecular oxygen and lipids, can give whiter appearance.
Malt flour and fungal alpha-amylase: a-amylase attacks a1-4 glycosidic links of amylase and amylopectin randomly, b- amylase attacks non reducing ends.
Sugar – substrate for yeast fermentation. High concentrations retard the growth of yeast due to osmotic affect.

Question 33

biochemical and rheological changes during breadmaking

Answer 33

Water absorption and dough development
Hydration of damaged starch
Fermentation
Flavour and aroma development

Question 34

Bread making process

Answer 34

Ingredient mixing, dough making (bulk fermentation, mechanical dough development, chemically activated dough development), rounding, moulding, proofing, baking, cooling

Question 35

Frozen dough production

Answer 35

Dough developed at 20°C instead of 27°C, transferred to freezer at -15°C, stored at -15° to -20°C for up to 8 weeks, thought at 5°C for 16 hours, proofed at 32 to 43°C at 75° humidity for one hour.

Question 36

Bread staling

Answer 36

Property changes with age, increase in bread firmness and crumbliness, starch crystallinity, loss of flavour, 8% lost due to staling, caused by transformation of starch chemistry

Question 37

Microbial spoilage of bread and prevention

Answer 37

Vegetative cells of bacteria killed during baking, surviving spores can germinate and cause spoilage known as rope, ropy spoilages of yellow brown spots on the crumb caused by the bacillus subtilise, ropy and fungal spoilage can be inhibited by calcium propionate or acetic acid

Question 38

Biscuits

Answer 38

Common features – baked to moisture content of less than 5%, enriched with fat and sugar.
Variations – methods of dough development, formation of dough piece, texture, flavour, additional ingredients used.
Categories – products that have fully developed gluten networks, products in which gluten networks are partially developed and are modified during processing, products in which there is no developed network.

Question 39

Ingredients of biscuits

Answer 39

Flour – crackers hard wheat medium protein 9.5 to 10.5%, hard sweet flour low-protein 8.5 to 9.5% soft wheat, biscuits soft wheat with protein of 8 to 10%.
Sugars and syrups – Maillard reaction, undissolved crystals form supercooled glasses upon cooling and increase crispness.
Fats and wheels – third largest component, dough, creams, coatings, surface spray, release agent’s, shortening flour, flour particles are coated with facts and interrupts flour/water network, texture less hard, retains gas cells, creates distinct layers,
Emulsifiers – increase softness, reduction in fat levels, improve tolerance of dough handling machines to variations in flour quality, allows fat a wider range of melting points.
Dairy products – flavours, high-protein, Maillard reaction.
Eggs – protein and fat, foaming ability – essential for batters.
Leavening agents - yeast, Chemical agents, bicarb, used with acids, sodium acid aluminium phosphate or GDL.
Salt – 1 to 1.5%, toughens gluten, less sticky dough

Question 40

Biscuit Manufacturing processes

Answer 40

Dough making – ingredients are mixed and dough allowed to ferment, fully developed gluten networks are formed.
Sheeting, laminating, cutting –
Baking – gives crackers their texture, dries the products, colours the services.

Question 41

Biscuit types

Answer 41

Heart sweet and semi sweet biscuits – characterised by a developed gluten network, relatively high levels of fat and sugar, extensive kneading to modify gluten structure.
Short dough and soft dough biscuits – made from a dough that likes extensibility elasticity and does not have a gluten network. Minimum kneading.
Wafers – water sheets are made from a batter, formed as large flat sheet,

Question 42

Oat milling processes

Answer 42

Dry shelling – cleaning and grading, stabilisation, drying, shelling by millstones, flaking cutting or grinding.
Modern impact shelling – cleaning and grading, shelling by impact, stabilisation, drying, flaking cutting or grinding.
Stabilisation – whole grains are stabilised by passing them through a steam chamber. Lipase inactivation can be checked by a tetrazolium test.
Drying/roasting – to increase the brittleness of the husk & to facilitate dehusking during shelling, partially degrade the starch and improve texture, develop characteristics flavour.
Flaking, cutting and grinding – oats first cooked in a steam cooker, temperature raised 100°C, moisture content increased to 10 to 12%, treatment and activate any remaining lipase activity.

Question 43

Corn milling

Answer 43

Dry milling – traditional process, corn kernel is separated into anatomical fractions.
Cleaning and conditioning, de-germing, grading drying and aspiration, milling and classifying.
Wet milling – corn kernel is separated according to its chemical composition.
Cleaning, steeping, de-germing, milling, separation of starch from protein.

Question 44

Methods of modifying starch

Answer 44

acid thinning –
Bleaching –
Cross-linking –
Substitution or derivatisation-
Pre-gelatinisated starch -

Question 45

Starch conversion

Answer 45

Involves the hydrolysis of starch by acid or enzymes.
The degree of starch conversion is measured by the dextrose equivalent of the solution.
DE is defined as the total reducing substances present in the solution calculated as glucose on a dry matter basis.
Acid hydrolysis –
Enzymatic process –

Question 46

Categories of breakfast cereals

Answer 46

Hot serve cereals – removal of fibrous materials, size reduction.
Ready to eat cereals – Fully cooked, require no additional cooking – flakes, shredded, puffed products.
Oat based cereals – rolled oats, quick oats, baby oats, instant oats.
Flight serial products – cornflakes, flakes from other cereals,
Puffed cereals – oven puffed rice, gun puffed rice, puffing by extrusion.
Shredded products
Granulated products
Sugarcoated products

Question 47

Quality of breakfast cereals

Answer 47

Low moisture content, usually 1 to 4%, microbiologically stable.
Moisture absorption results in lack of crispness.
Lipid oxidation leads to development of rancidity