Cereal Products and Their Nutritional Values PDF

Cereals and their products Prof. Cheng Li 1  Rundo wn 1. General background and significance 2. Composition and nutritional values 3. Growth, harvest, storage 4. Major cereal grains and their common products 10 ...

Cereals and their products Prof. Cheng Li 1  Rundo wn 1. General background and significance 2. Composition and nutritional values 3. Growth, harvest, storage 4. Major cereal grains and their common products 10  Cereal grains are seeds of the cereal grasses in the grass family Poaceae (formally called Gramineae). Being regarded as ‘staff of life’, cereals continue to be by far the most important source (in terms of calories) of total food consumption. (FAO. http://www.fao.org/3/y4252e/y4252e04b.htm#TopOfPage).  The share of dietary energy derived from cereals World Health Organisation https://www.who.int/nutrition/topics/3_foodconsumption/en/index1.html Types of cereal grains  Major food crops 1. Wheat ( 麥 ) 2. Rice 3. Corn 4. Barley ( 麥 ) 5. Sorghum ( 粱，蜀黍 ) 6. Millet ( 黍 / 稷 ) 7. Oats ( 燕麥 ) 8. Rye ( 麥﹐裸麥 ) World grain production (Food and agricultural organisation of united nation, 2009)  Figure 3.9 Aggregate consumption of cereals, by category of use FAO. 3.2.2 Prospects for the cereal sector http://www.fao.org/3/y4252e/y4252e05a.htm#TopOfPage  Rundo wn 1. General background and significance 2. Composition and nutritional values 3. Growth, harvest, storage 4. Major cereal grains and their common products 10  Individual kernel/ grain/ berry All kernels have similar structure. 11  Husk/ Chaff Rough outer covering. Protect from extreme temp, insects and etc. 12  Bran Hard outer （糠） covering, protecting endosperm. Excellent source of fiber & minerals. 13  Aleurone layer Protein, phosphorus, thiamin and other B vitamins, and some fat. Both bran and aleurone layer are removed in white flour. 15  Endospe rm The largest portion of the grain. Basis for all flours. Starchy, excellent source of complex carbohydrates. 16  Germ （胚 芽） At the base of kernel. Embryo, smallest portion. Rich in fat, some incomplete protein, vitamins and minerals, excellent source of vitamin B and E. Separated and sold as wheat germ. Susceptible to spoilage. Should be refrigerated. 17 Nutrie nt Conten ts image:https://simple.wikipedia.org/wiki/Bran 18  Nutrient Contents A cup of cooked cereal, grain or pasta: ~160 calories (30g carbohydrate, 6g protein, some vitamins and minerals, and a trace of fat) Carbohydrate: an excellent source of complex carbohydrates. Fiber: whole-grain products are a good source of soluble fiber and insoluble fiber. Whole grain products provide additional fiber. Fat: Very low in fat and no cholesterol. Vitamins and minerals: Low in refined grains; Possibly added back after milling; Phytate (physic acid) in unleavened bread can also interfere absorption. Protein: Incomplete because grains are low in lysine. Can be complemented by legumes. 19  Protein Quality High quality protein: include all essential amino acids 1. histidine 2. isoleucine 3. leucine 4. lysine (limiting a.a. in cereals) 5. methionine (limiting a.a. in legumes) 6. phenylalanine 7. threonine 8. tryptophan 9. valine 20 Complementary proteins Nutrients in Wheat Flour: Whole, Refined and Enriched Refining wheat flour removes many nutrients, including those listed here. Enriching replaces five nutrients. Source: http://wholegrainscouncil.org/files/backup_migrate/WGvsEnriched2011.pdf  Rundo wn 1. Background and significance 2. Composition and nutritional values 3. Growth, harvest and storage 4. Major cereal grains and their common products 23  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 (chaff) Winnowing: remove the grain from the chaff Combine Harvesters Threshing and winnowing by hand https://youtu.be/KjLCqahK2XY?t=12  Growing conditions Annual plants. One growing season per year, yielding one crop. Summer grains Winter grains (warm/ hot climate) (cold/cool climate) Wet / humid Corn, Rice Rye, Oat Dry / arid Spring wheat, Winter 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. image: http://himppi.or.id/2017/11/26/telat-uploud-artikel-inilah-pernyataan-admin-himppi-or-id/  Stora ge Dry grains without bran and germ are best kept in airtight containers in a cool, dry area free of rodents, insects and pests. (Moisture is the biggest contributor to deterioration) Most grains when stored properly can keep for 6-12 months. A relative humidity of 70% or less is considered safe. (Microbial growth when 75% or above) Whole grains should be refrigerated in airtight containers to retard rancidity and prevent mold growth. Cooked grains can be refrigerated and keep up to a week if they are tightly covered. Cooked whole grains can be frozen if they are tightly wrapped. Uncooked grains should not be frozen because freezing alters the protein structure.  Rundo wn 1. Background and significance 2. Composition and nutritional values 3. Growth, harvest and storage 4. Major cereal grains and their common products i. Rice ii. Wheat and Bread iii. Pasta and Breakfast cereals 31 4.1 Rice  Staple food Staple food for >3.5 billions people, particularly in Asia, Latin America, and parts of Africa. Scientists believe the first domesticated rice about 7000 years ago in China, India and Southeast Asia. The two largest rice producers are China and India as of 2023.  Factors that influence cooking Forms of grain: e.g. whole wheat berries take longer time than cracked Presence of bran or hull pH of Water: more alkaline water cooks grain faster Desired tenderness The factors above determine the amount of water used and the exposure to heat (heat intensity and cooking time). Textu re The secret to making good fried rice Grain length & texture Short: stickier, creamy Medium: stickier Long: drier 37  Why different textures? Stickiness: ratio of amylose and amylopectin Long grain: more amylose Short grain: more amylopectin image: http://blog.khymos.org/wp-content/2011/08/amylose-amylopectin.png  Glutinous rice Also called ‘sticky rice’ or ‘sweet rice’. Sweeter, stickier, more translucent and chewy than regular white rice when cooked. Easily shaped and moulded. Contain gluten?  Specialty A variety of longrice grain rice. Nuttier tastes, aromatic flavour, separate easily, more expensive. Basmati Jasmine Texmati Wehani  Brown, white & enriched rice Brown rice: only the husk is removed, leaving the bran and germ intact. Longer cooking time (more fiber) and tougher (crunchy & nutty) texture. White rice: most common. Milled to remove the bran and germ, removing all of the fiber, most of the B vitamins and vitamin K, and iron. Enriched rice Nutrients in Rice: Whole, Refined and Enriched Refining rice removes many nutrients, including those listed here. Enriching replaces four nutrients.  Converted rice (parboiled) Long-grained rice that has been soaked, steamed under pressure, and dried before milling or polish. Higher vitamin and mineral content compared with white rice. Account for 20% of all the rice sold in North US. Imports to HK by origin (2017) 1. Thailand 66.8% 2. Vietnam 16.8% 3. USA 5.8% 4. China 4.3% 5. Cambodia / Australia 1.8% https://www.tid.gov.hk/english/import_export/nontextiles/nt_rice/ monthly_rice.html (As of 30, Sept, 2017)  Rundo wn 1. Background and significance 2. Composition and nutritional values 3. Growth, harvest and storage 4. Major cereal grains and their common products i. Rice ii. Wheat and Bread iii. Pasta and Breakfast cereals 45 4.2 Wheat 14 different species with >30,000 varieties. 3 species account for 90% of world production: - common - club - durum  Growing seasons Winter wheat Spring Wheat Hard Soft High in protein Low in protein Durum wheat Common wheat Cakes, cookies, crackers & Bread and pasta production pastries  Farina ‘cream of wheatTM’ Wheat berries Rolled wheat Cracked wheat  Wheat Germ and Bran Wheat Germ: A good source of vitamin E (unless defatted), some B vitamins and fiber. Contain polyunsaturated fat. Turn rancid easily if not refrigerated. Wheat bran: A good source of dietary fibre, e.g. bread & muffin.  Wheat Flour 75% of wheat are made into flour; 25% are cereals, pasta products, animal feed, wheat germ and wheat germ oil Fine power obtained from crushing the endosperm of the grain. 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 ( 芋 頭 ), arrowroot ( 葛 ). 51  Wheat flour is the predominant choice, because of its protein structure that facilitates the rising of baked goods. Types of flour 53  Gluten flour usually used in combination with other flours to help heavy bread rise more readily and appear more fresh to customers. 54  Whole wheat flour includes bran, germ, and endosperm. Needs refrigeration. Bran’s coarse granules can cut the gluten strands, making bread dense and heavy. 55  Semolina flour made from the endosperm of durum wheat. Usually used to make pasta products. 56  All-purpose flour a blend of hard and soft wheat flours. Actual protein content may differ from region to region. Pastry flour and cake flour both have lower protein content, but cake flour contains more starch. 57  Flour Mixtures Simplest mixture: Water + flour. Additional ingredients: eggs, milk, fat, sugar, salt, flavouring, leavening agents. Types and proportions determine structure, volume, taste, texture, appearance & nutrient content. 58  Two major components: (1) Starch strengthens the baked item through gelatinisation and contributes to crumb. partially broken down by enzymes to add slight sensation of sweetness, darken the crust colour, and improve fermentation. 59 (2) Gluten protein Elastic, stretchy Contributes to the firming structure 60 https://www.youtube.com/watch?v=zDEcvSc2UKA  Gluten formation (1/2) Hydration: water draws out the gluten-forming proteins, i.e. gliadin and glutenin. 62  Gluten formation Kneading: (2/2) Compress and stretch the dough. The physical pressure of kneading stretches out the gluten molecules, increasing gluten strength (or elasticity) and giving dough a smooth, fine texture. 63 Hand Dough Kneading French Method http://youtu.be/PvdtUR-XTG0?t=30s  The rise of the flour mixture Dough rises as the gas (air, steam or CO2) entrapped by kneading expands, as a result stretching the gluten strands upward and outward. The heat during baking causes the gas to expand, which subsequently further expand the gluten.  Biological Leaveners Yeast: Saccharomyces Cerevisiae Multiply best at 20oC to 27oC while fermentation best takes place at 27oC-38oC. 66  Sug ar Provides food for yeast for fermentation Sweetens Adds moistness and tenderness Improves color (browning by dextrinization)  Sa Make doughs more elastic lt Add flavours and improves volume, texture & crumb by controlling yeast growth. Bread Staling 69  Rundo wn 1. Background and significance 2. Composition and nutritional values 3. Growth and harvest 4. Major cereal grains and their common products i. Rice ii. Wheat and Bread iii. Pasta and Breakfast cereals 70  4.3 Means ‘paste’ or ‘dough’ in Italian. Pasta Made predominately from flour starch & water. Naturally high in complex carb; low in fat and protein. Eggs, cheese, butter, oil, cream, meat and etc may be added. 71  Pasta is usually made from semolina, and/or farina. Semolina flour is derived from durum wheat, which contains higher protein content, that help withstand mechanical pressure and heat, resulting in elasticity and maintaining shape. Whole wheat: slightly higher in nutrients and fiber, but easier to disintegrate if cooked too long.  Fresh pasta has higher moisture content, softer consistency, shorter cooking time (3 vs 10 mins), and shorter shelf life. Dried pasta: cut and dried until the moisture level drops from 31% to 10% -12%.  Freshly made pasta dough is placed in a cylinder and forced through holes in small discs. Best extruded at 46oC because protein will denature at >60oC. Breakfast Cereals  Why different shapes? The majority of breakfast cereal is cold ready-to-eat cereal made from wheat, corn or oats. 78 https://www.ted.com/talks/rory_sutherland_life_lessons_from_an_ad_man/transcript?language=en#t-720925  References Brown, A. (2011) Cereal grains and pasta. In: Understanding Food: Principles and Preparation 4th edition Thomson/Wadsworth, Chapter 16, pp. 345-366. Brown, A. (2011) Flours and flour mixtures. In: Understanding Food: Principles and Preparation 4th edition Thomson/Wadsworth, Chapter 17, pp. 367-390. 81