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Week 12: Cereal Based Product Processing - Coggle Diagram
Week 12: Cereal Based Product Processing
Composition and Structure of Cereal Grains
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Cereal grains typically has the following composition but could vary depending on varieties, geographical and abiotic stresses
Carbohydrate : 58 – 72%
starch (amylose, amylopectin)
heating starch in excess water, gelatinisation occurs. It is a process in which starch becomes soluble, binds water and form a gel. This process makes starch easily digestible.
When wheat, corn or rice is added to water, starch granules begin to swell on heating. After granules rupture, starch is released.
Protein : 7 – 15%
gluten (except in rice)
Fat : 2 – 5%
Indigestible fibre: 2 – 11% (depends on processing)
Moisture : 10 – 14%
Basic structure
endosperm: rich in protein and starches is centrally located
bran (pericarp): hard protective covering
germ (embryo): located near the bottom.
Various structures in different grains
Corn seed
Wheat grain
Rice Grain
Food Technology Aspect of Cereals
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Milling: Mechanical separation of
endosperm
from germ, seed coat & pericarp resulting in intentional losses of micronutrients.
Affects technological and nutritional property of cereals
Flour with high extraction rate (The amount of flour produced from the given amount of grains. more of the bran, germ and outer layers of the endosperm in it) – more bran particles so higher micronutrients
High ER: at least 80%. Higher chance of bran entering into flour when attached to endosperm
Commercial milling removes approx. 70% of thiamine, 60-65% of riboflavin. Iron and zinc located at periphery of kernel are reduced too
Phytates/phytic acid usually located in the outer layer of cereals is also removed during milling
further processed into a diverse wide array of products such as bread, breakfast cereals,
where milling occurs. Different parts of the wheat are separated.
Gristing: Where different blends of wheat are mixed together.
Rice Processing
Types of rice
Brown rice (whole grain)
Enriched white rice (enriched with vitamin and minerals to restore nutrients after removal of hull, bran and germ)
Glutinous/waxy rice
Parboiled rice: partially boiled.
Parboiling is a process that involves soaking of paddy, steaming and drying
Steam-pressure treatment gelatinizes the starch and result in grains that are firmer, stable and less susceptible to overcooking.
often used for brown and white rice used in canned, frozen food and food service uses.
2 ways
Modern: soaked in hot water at 60℃ (below gelatinisation temp.) for few hours to reduce incident of aflatoxin contamination. Vacuum infilteration to de-aerate grain prior to pressure steam cooked.
Traditional: soak rough rice overnight in water at ambient temperature, boiling/steaming at 100℃ (gelatinise starch), cooled and sun dried before milling/storage
Changes During Parboiling:
Water soluble vitamin and minerals are driven from bran into kernel preventing nutrient loss
Enzymes present in kernel are totally or partially inactivated
Starch granules are gelatinized and expanded filling the surrounding air spaces
Prevent proliferation of fungal spores, growth of egg or larvae of insects
Advantages
High milling yield and better rice quality
Increase shelf life
Resistance to attack by insects
Higher nutritional value
Firmer texture and less sticky after cooking
Disadvantages
High operating cost
Difficult to mill since kernel more slippery
Increase cooking time
Wheat Based Product
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Example: Bread
Ingredients :check:
Wheat flour
Wheat is converted to flour prior to human consumption.
Clean, temper/condition (15-17% moisture)
Milling is a progressive series of disintegration (size reduction) of grains
sieving (separation).
Flour from conventional milling may be further reduced in size through turbo milling.
After turbo milling, finer protein particles and starch particles may be separated using air classifier.
1 more item...
classified as hard and soft type.
Hard wheat ~ higher in protein (more gluten), stronger flour, elastic dough (application: bread, pasta)
Soft wheat ~ lower in protein, weaker flour, weak dough/batter (application: cake, biscuits, pastry)
Contains
Gluten (functional protein): when moist and worked by mechanical action form an elastic dough through formation of linkages between protein molecules.
Upon exposure of sufficient heat, gluten coagulates and forms a rigid structure.
When you keep on kneading the dough, it will turn less elastic due to frequent breaking and reassociation of disulfide bonds
Whole wheat dough, the bran pieces are physical barriers in gluten formation. Denser dough
Gluten gets dissolved in alcohol.
Starch
does not form elastic film similar to gluten.
moist starch when heated will gelatinise (form paste and stiffens).
Water
One of the major ingredients used for hydration of gluten and starch. Water absorbing capacity of flour will determine the amount of water. Low water should be avoided since it will result in a tight dough and cause smaller volume and heavy texture.
Upon addition of water, starch particles are hydrated and dough is formed. Subsequently water starts to hydrate the 2 proteins (glutenin and gliadin) forming gluten.
Hardness of water (mineral content) affects dough characteristics. E.g. hard water (high minerals), dough exhibits high strength and fast fermentation.
Leavening agents
Air
in dough expands during heat contributes to leavening
Steam
Water in dough turns to steam during baking and expanding steam contributes to leavening
Baking powder
sodium bicarbonate (CO2 source) and baking acid (mono-calcium phosphate)
Yeast
Moist pressed or dehydrated living cells of Saccharomyces cerevisiae.
When hydrated, give CO2 as by-product during fermentation to enable dough to rise
Expand cellular network of dough to form breadcrumb
Provide characteristic flavour and aroma from alcohol produced in fermentation
Egg
Mixture of protein. Form film and entrap air when whipped. Upon heating will coagulate to give rigidity. (Esp. important in preparation of angel cake and sponge cake)
Other than nutrients/flavours/colour, it affects texture and contributes as principal structure builder
Sugar
Contributes to sweetness and colour in baked goods. Also, provides fermentable substrates to yeast.
Salt
Flavour, strengthen gluten, control yeast fermentation and retain moisture to reduce staling.
Must not come into direct contact with yeast
Shortening/Fat
Serve as “tenderizer”, lubricate texture, shortness to cake crumbs.
Fats affects gluten formation by creating coating around proteins.
Blending of fat will entrap air and during heating the shortening will melt and release air bubbles. The melted fat also form deposits around cell wall.
Left: Cake batter with shortening. Right: Cake batter without shortening . Note that left have more air bubbles than right
Emulsifier
Improve dough stability, maintain softeness and improve loaf volume and crumb structure.
Emulsifiers
25 increased the number of bubbles incorporated during mixing, o
emulsifiers tend to increase the number of gas cells with
29 lower size in the bread crumb, but led to greater crumb firmness, which suggested
30 different interactions between emulsifiers and gluten, affecting protein polymerization
31 during baking.
In bread: Mono- and di-glycerides of fatty acids as E471 Diacetyltartaric and fatty acid esters of glycerol as E472e Sodium stearoyl lactylate as E481 (i)
Ascorbic acid (E300 or vitamin C)
Strengthen dough, increase softness of bread and beneficial effect on volume and crumb structure
Processing
Proofing (Fermentation): Ferment at controlled temperature and humidity to allow yeast to convert glucose to carbon dioxide and alcohol.
Knocking back: Expel gas to reduce size of gas bubbles (esp. large gas holes) by kneading to give better shape and volume. Enable formation of stable crumb structure.
Kneading: Stretch and develop gluten structure.
Excessive weakens gluten films while insufficient unable to hold structure resulting in dense loaf
Dividing & Moulding
Mixing: ensure dough is soft and smooth prior to kneading process.
Baking
Evolution and expansion of gases
Coagulation of protein (gluten and egg)
Gelatinisation of starch
Development of flavour/colour
Evaporation of water
Processing
Traditional bulk fermentation method
Ingredients mix to form a dough. Dough left to ferment for up to 3 hours before moulding and baking
Mechanical dough development method (Chorleywood Process)
Uses mechanical energy by mixing at high speed to develop dough to reduce fermentation and proving time to approx. 1 hour. Higher levels of yeast and presence of oxidizing agents (e.g. ascorbic acid), hard fat, emulsifier and enzymes.
Modern commercial process used in large bakeries developed in 1961 by British Baking Industry Research Association at Chorleywood.
Benefits
Reduce processing time, increase productivity
Save space by eliminating use for bulk fermentation
More consistent product quality
More profit as higher dough yield by adding extra water
Finer crumb structure, softer due to thinner cell structures and ability to maintain softness longer
Differences:
typically consists of flour, water, salt, fats, dairy ingredients, egg, permitted emulsifier, stabilizer and preservatives.
Principal application is bakery products. 4 categories :check:
Partially leavened : Slightly leavened due to expansion of steam and other gas
E.g. pie crust, crackers
Air-leavened: Leavened by air entrapped inside
E.g. sponge cake, angel cake
Chemically leavened: Leavened by CO2 from baking powders/chemical agent
E.g. biscuits, doughnut
Yeast-raised: Leavened by CO2 from yeast fermentation
E.g. Bread
