Presentation on theme: "CHAPTER 4:. What is a cereal? (definition) The term ‘cereal’ describes any cultivated grass that produces an edible grain. In many countries a type of."— Presentation transcript:
What is a cereal? (definition) The term ‘cereal’ describes any cultivated grass that produces an edible grain. In many countries a type of cereal grain is generally a dietary staple including: Wheat Oats Barley Rye Corn (maize) Sorghum Millet Rice
WHEAT Has traditionally been the main cereal grown and used in Australia Rice has become popular in recent years Cereals are important in the food industry Used in breads, pastas, noodles.
CEREAL GRAIN STRUCTURE A cereal grain has three layers: 1) Bran/husk – fibrous outer covering (13% of grain) 2) Endosperm Largest part (85%) storage cells, stores starch 3) Germ Smallest part (2%) Part of the grain which new grains grow.
1. WHEAT Grown throughout the world Most popular cereals produced Wheat grain is usually ground into flour (main ingredient of bread, pasta, noodles, cakes) Glutelin & gliadin are the main proteins in flour (they combine to produce protein GLUTEN). Gluten gives dough ____________ Soft Wheat= less gluten (cakes & biscuit) Hard wheat = > level of gluten (bread & pasta)
Main products made from wheat? Wholemeal flour (wholegrain – bran, endosperm and germ) White flour (milled from the endosperm) Cornflour (finely ground endosperm) Wheat bran (outside husk of grain) Burghul (cracked wheat) Semolina (inner starchy endosperm) Wheat germ (germ) See page textbook for pictures
2. RICE Mainly grown in Asia More grown in Australia due to increase demand Available in two main forms: 1) Brown rice – unprocessed (whole grain)bran, germ and endosperm 2) White or polished rice (endosperm) * Rice is gluten free so suitable for people with coeliac disease.
Main products made from rice: Rice flour/ground rice Rice noodles
3. CORN/MAIZE Grown as corn on the cob and used as a fresh vegetable or as field corn that is harvested and ground to make flour. Corn is gluten free Main products from corn: Cornflour (fine flour used for thickening agents in sauces) Sweet corn Popcorn (dried wholegrain) Cornflakes (kernels are baked and rolled) Ground corn (tortillas, corn chips) Polenta (Italian porridge)
4. OATS Small proportion of Australia’s cereal production Contain some gluten Used to produce products such as rolled oats (porridge), oat bran, muesli, biscuits (Anzac) Majority of oats produced in Australia used for stock feed
5. RYE Popular in Scandinavian countries/Russia Hardy cereal used in the ‘heavier’ breads Rye flour is dark, lower in protein Rye flour used to make pumpernickel and some crisp breads
STORAGE OF CEREALS Described as ‘Non-perishable’ or safe foods because they can be stored for long periods. Have low moisture content (difficult for bacteria to grow) Rice, flour & pasta stored in cool dry conditions Stored in airtight containers Can be infested with weevils, ants/rodents
NUTRITIONAL PROPERTIES OF CEREALS Excellent source of complex carbohydrates (contain both starch and dietary fibre) Wholegrains – protein, Vitamin B Bran – dietary fibre
TYPES OF WHEAT FLOUR Type of flourPhysical, chemical & sensory properties Uses White plain flourAll purpose flour. 10-11% protein Baking, thickening,coating Self-raising flourPlain flour + leavening agent – causes to rise Cakes, muffins, biscuits Wholemeal flourPlain/SR. Products are dense and darker. Cakes, pastry, bread Bread flourProtein 10-15%Bread, pasta, pizza
Functional Properties of wheat flour Properties of starch and protein give a range of properties in food preparations: Volume – bread, cakes, biscuits. Thickening – starch present will swell, thicken and form a gel when heated in liquid (GELATINISATION). Gravies, custard powder. STRUCTURE – protein gluten enables baked products to hold their structure (bread making). CONTRIBUTION OF COLOUR – starch contributes to browning of bread when toasted/baked. This is called ---- DEXTRINISATION MOISTURE ABSORPTION – absorbs liquids which helps bind ingredients together during cake and bread making.
DEXTRINISATION Starch + dry heat = DEXTRINISATION Is the browning of starch foods when dry heat is applied. This process occurs when bread is toasted. Dextrins form in flour products during baking. The crust that forms on bread and cakes during baking is the result of DEXTRINISATION.
Many sensory changes occur as a result of dextrinisation of starches: Colour – golden brown eg: when bread is toasted Flavour – sweet taste. Excessively heated will taste ‘burnt’ Aroma – a desirable or ‘cooked’ smell eg: freshly baked cakes Texture – and mouthfeel change when dextrinisation occurs. Food becomes crisp. Eg: soft fresh bread dough becomes crisp during baking due to the process of dextrinisation.
Comparing the dextrinisation process in a variety of breads 1. Select a range of breads (Rye, white, wholemeal) 2. Use toaster toast each bread product. 3. Record the time taken for this process to occur. 4. Taste each product.
Comparing the dextrinisation process BREAD PRODUCT TIME TAKEN TO BROWN COLOUR: LIGHT/GO LDEN/DA RK IMPACT ON FLAVOUR TEXTURE RYE WHITE WHOLEMEAL RAISIN
GELATINISATION Starch + wet heat = Gelatinisation Is the process that causes starch granules to swell and thicken when heated in a liquid. When starch grains are heated in this way they form a ‘gel’.
Heat starch granules in liquid Starch granules become swollen Starch granules burst The liquid thickens and gelatinises Starch gelatinises when heated in a liquid, producing a thickened liquid
Syneresis On standing and cooling, many gels lose liquid and shrink. This is known as ‘weeping’ or ‘syneresis’.