Cereals and Their Products PDF

Cereals and Their Products -Cereal grains are seeds of the cereal grasses in the grass family Poaceae -Regarded as “Staff of life” and it continue to be by far most important source in terms of calories of total food consumption -About ~50% of dietary energy derived from cereals globally Major fo...

Cereals and Their Products -Cereal grains are seeds of the cereal grasses in the grass family Poaceae -Regarded as “Staff of life” and it continue to be by far most important source in terms of calories of total food consumption -About ~50% of dietary energy derived from cereals globally Major food crops: 1. Wheat 2. Rice 3. Corn 4. Barley World grain production 1. Corn (Maize) 32% 2. Rice 29% 3. Wheat 28% Consumption: Developing countries > Industrial countries > Transition countries Structure Usage (Individual kernel/ grain/ berry) -All kernels have similar structure l Rough outer covering l Protect from extreme Husk/Chaff temperature, insects and etc. l Usually not edible l Hard outer covering protecting endosperm Bran (糠) l Excellent source of fiber and minerals l Protein, phosphorus, thiamin and other B vitamins and some fat Aleurone layer l Both bran and aleurone layer are removed in white flour l Largest portion of the grain l Basis for all flours. Endosperm l Starchy, excellent source of complex carbohydrates Germ (continued from structure) l At the base of kernel l Embryo, smallest portion. Rich in fat, incomplete protein, vitamins and minerals, excellent source of vitamin B and E l Separated and sold as wheat germ l Susceptible to spoilage and should be refrigerated Nutrient contents of cereal grains 1. Carbohydrate: an excellent source of complex carbohydrates 2. Fiber: Whole-grain products are good source of soluble fiber and insoluble fiber, whole grain products provide additional fiber 3. Fat: Very low in fat and no cholesterol 4. Vitamins and minerals: Low in refined grains but possibly added back after milling. Phytate (Physic acid) in unleavened bread can also interfere (妨礙) absorption. 5. Protein: Incomplete since grains are low in lysine and can be complemented by. legumes. (Complementary protein) Harvest and growth -Grains are seeds harvested from dead, or dry, grasses -Cutting: remove grains from the stalk of grass Threshing: loosen the edible grain from its casing Winnowing: remove the grain from the chaff Growing conditions -Annual plants and one growing season per year, yielding one crop Summer grains Winter grains (Warm/ hot climate) (Cold/cool climate) Wet/ humid Corn, Rice Rye, Oat Winter wheat Dry/ arid Spring wheat, Sorghum (e.g. Durum wheat) -Rice paddies: >90% of rice are grown with its roots submerged in water and is known as lowland, wet or irrigated rice -Highland, hill or dry rice is grown in areas of plentiful rain. E.g. Vietnam, Indonesia, China, Thailand and etc. Storage l Dry grains without bran and germ: Best kept in airtight containers in a cool and dry area free of rodents, insects and pests. Most grains can keep for 6-12 months if stored properly. l Relative humidity of 70% or less (Microbial growth when 75% or above) l Whole grains: Refrigerated in airtight containers to retard rancidity (酸敗) and prevent mold growth l Cooked grains: Refrigerated and keep to a week if tightly covered l Cooked whole grains: frozen if tightly wrapped, uncooked grains should not be frozen as freezing alter the protein structure Specialty rice -A variety of long grain rice, nuttier tastes, aromatic flavor, separate easily and more expensive E.g. Basmati, Jasmine, Texmati, Wehani Brown, White and Enriched rice l Brown rice: only the husk is remove leaving the bran and germ intact. Longer cooking time (more fiber) and tougher (crunchy and nutty) texture. l White rice: most common, milled to remove the bran and germ, removing all fiber, most of the B vitamins and vitamin K, and iron. l Enriched rice: Adding back nutrients Converted rice l Long-grained rice that has been soaked, steamed under pressure and dried before milling or polish. l Higher vitamin and mineral content compared with white rice l Account for 20% of all the rice sold in North US. Imports to HK by origin (2017) Thailand (66.8%) > Vietnam (16.8%) > U.S.A. (5.8%) > China (4.3%) > Cambodia/Australia (1.8%) Wheat -14 different species with >30000 varieties -3 species account for 90% of world production 1. Common 2. Club 3. Durum Growing seasons Winter wheat Spring wheat Hard Soft High in protein Low in protein Durum wheat Common wheat Bread and pasta production Cakes, cookies, crackers, and pastries Wheat Germ: Good source of Vitamin E (unless defatted), some B vitamins and firber. Contain polyunsaturated fat, turn rancid easily if not refrigerated Wheat bran: Good source of dietary fiber, e.g. bread and muffin Wheat Flour l 75% of wheat are made into flour, 25% are cereals, pasta products, animal feed, wheat germ and wheat germ oil l Fine powder obtained from crushing the endosperm of the grain l Whole grain flours: bran and germ are also milled into the flour Different types of Flour -Any grain can be used to make flour e.g. oat, rye, barley, rice, corn -Non-grain sources: soy, potato, taro, arrowroot Wheat flour is the predominant choice because of its protein structure that facilitates the rising of baking goods Different types of wheat flour l Gluten flour: usually used in combination with other flours to help heavy bread rise more readily and appear more fresh to customers. l Whole wheat flour: Includes bran, germ and endosperm, need refrigeration Bran’s coarse granules can cut gluten strands making bread dense and heavy l Semolina flour: Made from the endosperm of durum wheat, usually used to make pasta products. l All-purpose flour: A blend of hard and soft wheat flours, protein content may differ from region to region. l Pastry flour and cake flour: Both have lower protein content but cake flour contains more starch. Flour mixtures l Simplest mixture: Water + flour l Additional ingredients: eggs, milk, fat, sugar, salt, flavoring, leavening agents l Types and proportions determine: structure, volume, taste, texture, appearance and nutrient content. Two major components: (1) Starch l Strengthens the baked item through gelatinization and contributes to crumb l Partially broken down by enzymes to add slight sensation of sweetness, darken the crust color and improve fermentation (2)Gluten protein l Elastic, stretchy l Contributes to the firming structure Gluten formation -Hydration: water draws out the gluten-forming proteins i.e. gliadin and glutenin -Kneading: Compress and stretch the dough. Physical pressure of kneading stretches out the gluten molecules, increasing gluten strength (or elasticity) and giving dough a smooth, fine texture Rise of the flour mixture l Dough rises as the gas (air, steam or CO2) entrapped by kneading expands, as a result stretching the gluten strands upward and outward. l The heat during baking causes the gas to expand, which subsequently further expand the gluten. Biological leaveners -Yeast: Saccharomyces Cerevisiae -Multiply best at 20C to 27C while fermentation best takes place at 27C to 38C Sugar l Provides food for yeast for fermentation l Sweetens l Adds moistness and tenderness l Improves color (browning by dextrinization) Salt l Make dough more elastic l Add flavor and improves volume, texture and crumb by controlling yeast growth Pasta -Means “paste” or “dough” in Italian -Made predominately from flour starch and water -Naturally high in complex carbo; low in fat and protein -Eggs, cheese, butter, oil, cream, meat and etc. may be added l Pasta usually made from semolina, and/or farina l Semolina flour derived from durum wheat which contains higher protein content, help withstand mechanical pressure and heat, resulting in elasticity and maintain shape l Whole wheat: slightly higher in nutrients and fiber but easier to disintegrate if cooked too long l Fresh pasta: has higher moisture content, softer consistency, shorter cooking time and shorter shelf life l Dried pasta: cut and dried until moisture level drops from 31% to 10%-12% l Best extruded at 46C because protein will denature at around 60C Breakfast cereals l Most of them is cold ready-to-eat cereal made from wheat, corn or oats.