Family and LifeStyle -...
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Transcript of Family and LifeStyle -...
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Family and LifeStyle
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Food Commodities
6 Food Commodities6.1 Cereals
6.1.1 Wheat
6.1.2 Rice
6.1.3 Maize (Corn)
6.1.4 Barley
6.1.5 Oats
6.1.6 Rye
6.2 Fruits
6.2.1 Types of fruit
6.2.2 Nutritional Value of Fruits
6.3 Vegetables
6.3.1 Structure of a plant cell
6.3.2 Nutritional Value of Vegetables
6.3.3 Types of vegetables
Contents Page
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9 食物腐壞和食物中毒9.1 食物腐壞的原因
9.1.1自然腐爛
9.1.2 微生物污染
9.2 食物中毒的�因
9.2.1 生物性食物中毒
9.2.2 細菌性食物中毒
9.2.3 化學品導致的食物中毒
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Contents Page
6.4 Meat and their offals
6.4.1 Meat
6.4.2 Offals
6.5 Poultry
6.6 Fish
6.6.1 Types of fish
6.6.2 Nutritional Value of Fish
6.6.3 Preparation of fish
6.7 Eggs
6.7.1 Hen’s Eggs
6.7.2 Preserved eggs
6.8 Dairy products
6.8.1 Milk
6.8.2 Cheese
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9 食物腐壞和食物中毒9.1 食物腐壞的原因
9.1.1自然腐爛
9.1.2 微生物污染
9.2 食物中毒的�因
9.2.1 生物性食物中毒
9.2.2 細菌性食物中毒
9.2.3 化學品導致的食物中毒
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Contents Page
6.8.3 Cream
6.8.4 Yoghurt
6.8.5 Butter and Margarine
6.9 Soya Bean and Soya Bean products
6.9.1 Nutritive value of soya beans
6.9.2 Soya bean products
6.10 Sugars (honey)
6.10.1 Types of sugar
6.10.2 Uses of sugar in food preparation
6.10.3 Examples of food with high sugar content
6.11 Cooking fats and oils
6.11.1 Types of fatty acids
6.11.2 Examples of food with high fats and oil content
6.12 Food composition table
6.12.1 What information can you find in a food composition table?
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9 食物腐壞和食物中毒9.1 食物腐壞的原因
9.1.1自然腐爛
9.1.2 微生物污染
9.2 食物中毒的�因
9.2.1 生物性食物中毒
9.2.2 細菌性食物中毒
9.2.3 化學品導致的食物中毒
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6 Food CommoditiesFood Commodities
Foods can generally be classified as raw (fresh) or processed foods. All foods contain nutrients, including ‘junk foods’. Some foods have higher nutritive value in which the nutrient content of the food fit our body’s nutrition requirement. Raw or fresh foods are called primary foods, which have received little or no processing. For example, fresh fruits and vegetables, fresh meat, offals, fresh seafood and pasteurised milk (primary processing) are primary foods. Processed foods are called secondary foods, which have received more complex processing that make them into composites or products. For example, bakery products (breads & cakes), canned soups, fruit juice and dried/frozen/canned fruits and vegetables, ham, bacon, sausages, salted fish are secondary foods.
6.1 Cereals
Cereals are the grain or seeds of cultivated grasses. Cereals grains are the world’s cheapest source of food energy and provide two-third or more man’s energy and protein intake. Cereals may be used as grains, e.g. rice, or they can be ground into flour, e.g. wheat flour. The most important cereals are wheat, rice, maize (corn), barley, oats and rye.
Cereals are also known as ‘staple foods’ as they often make up the bulk of the diet since they are relatively cheap to produce e.g. rice is a staple food for a large part of the world’s human population, especially in East, South and South-east Asia, whereas bread and pasta are staple foods that are commonly eaten in the western countries. All kinds of vermicelli, noodles and rice such as red rice, brown rice, plain rice, bread and crackers can be regarded as good sources of grains.
Cereals and cereal products are valuable source of carbohydrate, protein and dietary fibre. They also contain a range of micronutrients such as vitamin E, some of the B vitamins, sodium, magnesium and zinc.
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6.1.1 Wheat Wheat is a main cereal food in many countries and it is regarded as the most versatile and nutritious of all cereals. Wheat is usually milled to make flour. The type of flour produced differs according to the rate of extraction. The percentage of the grain used in the flour is called the extraction rate of the flour.
As hard wheat produces strong wheat flour with a high protein content, it has a high gluten content, which is ideal for mixtures that must have elastic, stretchy dough, such as bread, pasta and flaky pastries. While soft wheat produces soft wheat flour with less protein, it has a low gluten content, it is more suitable for general cooking including cakes, biscuits and shortcrust pastries. Wheat flakes are used for porridge, muesli and flapjacks. Wheat germ is an excellent source of nutrients, especially vitamin E.
(A) Structure of a wheat grainThe individual wheat grain is small, oval in shape with a tuft of hair projecting from the top. A wheat grain consists of 3 major parts: endosperm, germ and bran. At the point at which it was attached to the stalk is the germ. The grain is protected with a double layer of bran. Inside this is the aleurone layer which is largely composed of protein. The central part of the grain consisted of the endosperm which contains starch cells closely packed and interspersed with the protein known as gluten.
Table 6.1 Examples of cereals and cereal products:
Cereals
Wheat
Rice
Maize (corn)
Barley
Oats
Rye
Cereal Products
Bread
Rice noodles
Popcorn
Pearl barley
Rolled oats
Rye bread
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(B) Types of flour
(i) White flour
This consists mainly of starch with some protein mainly gluten, and reduced amount of B group vitamins. As the germ which contains the fat is removed, the flour keeps for a long time. White household flour on sale is called plain flour and has a 73% extraction rate.
(ii) Self-raising flour
A raising agent such as baking powder has been added to self-raising flour for convenience. The disadvantage of it is that while self-raising flour contains the average amount of raising agent for general bread and cake-making, this may be too little for some recipes. Self-raising flour should not be used for pastry or for baking where yeast is employed.
(iii) Wholemeal flour
This contains the whole grain which is crushed after cleaning. Wholemeal and wheatmeal flours are rich in B group vitamins and contain more iron, calcium, fat and cellulose than white flour. In fact, the more thoroughly the grain is milled the greater the reduction in food value. Calcium, phosphate and improvers such as ascorbic acid are generally added after milling as they are lost in high-extraction-rate flours. Wholemeal flours do not keep as well as white flours because of the presence of fat and the slightly higher moisture content.
Figure 6.2 Structure of a wheat grain
germ
bran
endosperm
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(iv) Stone-ground flour
Wheat ground between stones is said to be superior in taste and food value to flours produced by break-rolling, as smaller amounts of B vitamins are lost. Most stone-ground flour is sold in health food shops and is often ground from “organically” grown wheat.
(v) Starch-reduced flour
Some of the starch is removed by washing, leaving a higher proportion of protein and other nutrients. This is ideal for those who are slimming. “Energen” products are made from this type of flour.
(vi) Wheat germ flour
A mixture of white flour and cooked germ, which gives a malt flavour to bread. It is used in smooth-texture brown bread such as “Hovis”.
(vii) Gluten-free tang flour
This is used by those who suffer from coeliac disease. White flour is washed so that the starch is removed. This starchy liquid is dehydrated to produce gluten-free flour.
Gluten is the main protein present in wheat. When mixes with water it becomes a sticky, elastic substance which makes it ideal for bread-making. When air or carbon-dioxide bubbles are trapped in the dough, they expand in the heat of the oven. Once the dough becomes hot enough, the gluten like all protein, coagulates around the air bubbles sets the bread. Barley and rye contain small amount of gluten, but flour from most other cereals, e.g. cornflour, rice, does not contain any and cannot therefore be used in baking unless when combined with wheat flour.
Additional Information
(viii) Strong flour
This flour has a high percentage of gluten and gives better results in yeast baking and puff pastry. Canadian spring wheat is over 12 percent gluten. If a high proportion of this wheat is blended with normal wheat (9% gluten), the resulting flour will be strong or hard. Flour made from European wheat is soft and more suitable for cakes.
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Additional Information
Advantages of wholemeal flour1. The nutrient content of the grain is retained2. The bran provides a valuable source of fibres3. The flour gives a pleasant “nutty” flavour to baked items
Disadvantages of wholemeal flour1. It does not keep for as long as white flour due to the fat content which can become rancid relatively quickly2. The presence of phytic acid may affect the absorption of calcium and iron3. It does not have such good baking qualities as white flour for items such as pastry and cakes
Advantages of white flours1. It has good baking qualities, producing a fine texture in cakes, bread and pastry2. It contains less phytic acid3. It contains less fat and is therefore less likely to become rancid
Disadvantages of white flour1. It contains less fibres2. It contains less calcium and iron, although by law these are added to flour used for making bread3. It contains less protein and vitamins
6.1.2 RiceMost types of rice are available as unpolished rice (i.e. brown / wholegrain rice) or polished rice (i.e. white rice). Brown rice is the whole grain of rice, with the outer husk removed. White rice is milled and polished to remove the bran and germ, so it looks shiny (pearly). Because of this, it is less nutritious than brown rice, having fewer B vitamins, minerals, and proteins, and less dietary fibre. Brown rice takes longer to cook than white rice. It has a nutty flavour and a more chewy texture.
For cooking, there are two basic types of rice: long- and short-grain rice. Long-grain rice such as Carolina rice and Basmati remains fluffy, firm and separate when cooked, so it is best for savoury dishes e.g. Basmati in Indian curry dishes. Short-grain rice becomes softer and sticker when cooked, so are best for rice puddings (Pudding rice) and risotto (Arborio rice).
Rice can be ground to make rice flour, but because of the lack of gluten, it cannot be used to make leavened bread but can be used for cakes, biscuits, pancakes, Japanese rice wine (saké) and rice noodles.
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6.1.3 Maize (Corn)Maize is generally more resistant to drought and gives a higher yield than wheat. It is a gluten-free cereal and is usually consumed as a vegetable (corn on the cob, corn kernels); as breakfast cereals such as cornflakes; as cornflour / cornstarch for thickening; as snack foods such as popcorn (salted or sweetened), as cornmeal to make polenta which can be added to soup, pancakes, muffins; as tortillas that are made from ground maize. Its germ is rich in oil, and can be refined to produce corn oil. The nutritive value of maize compares unfavourably with that of wheat. It is relatively poor source of nicotinic acid and protein.
Maize meal is about 96% extraction and is used to make porridge. Maize flour is 60% extraction. The proteins of maize flour are non-gluten-forming protein and are unsuitable for bread-making.
6.1.4 BarleyBarley is one of the hardest of cereals. It is mainly sold as pearl barley, which is the whole grain with its husk removed. Barley flour is ground pearl barley. As barley has a low protein content which means little or no gluten is produced, it is not used to make flour. Barley is also used in soups, stews and barley water; and as well as animal feed or for making beer and whisky.
Malt and malt product are made from germinated barley or wheat. Malt products are used in the food industries for making biscuit, cakes and special breads. Malt feeds the yeast, improve bloom, flavour and keeping quality of bread.
6.1.5 OatsThe oat, like some other cereals, has a hard, inedible outer husk that must be removed before the grain can be eaten. Oats can be rolled or processed into oatmeal (rolled oats), or ground into fine oat flour to produce a variety of products e.g. rolled oats to make porridge and oatcakes, oat flour to make baby foods and breakfast cereals like muesli and granola. Oat is low in gluten so cannot be used to make bread, but are good for biscuits and porridges; and can also be mixed with wheat flour to add flavour and texture to bread, muffins, pancakes etc. Oatmeals have some husk removed and come in three grades: coarse, pinhead and fine.
6.1.6 Rye Rye can be milled to produce flour. It contains less gluten than wheat, so it produces bread with low volume and a dense texture such as the German black bread called pumpernickel. Rye is also used to produce crispbreads and alcohol. To increase the strength of the flour it is common to mix rye flour with wheat flour to make rye bread.
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6.2 Fruits
6.2.1 Types of fruit(A) Fleshy fruits e.g. apple, guava, pear, e.g. bananas, cantaloupe, water melon, papaya, pineapple(B) Soft or berry fruits e.g. blackberries, black currants, blueberries, gooseberries, grapes, loganberries, raspberries, redcurrants, strawberries (C) Fruits with stones e.g. avocado, cherries, dates, plum, prune, apricot, nectarine, peach (D) Citrus fruits e.g. orange, lemon, lime, mandarin, tangerine, grapefruit, kumquat, pomelo
6.2.2 Nutritional Value of FruitsFruits are generally high in water, dietary fibre and vitamin C. Blackcurrants, oranges, lemon, grapefruits and strawberries are particularly rich sources of vitamin C. Apple, pears, plums and peaches are among the fruits with a relatively low vitamin C content.
Fruits have higher sugar content than vegetables and ripe fruits contain little or no starch. Grapes, for example, contain up to 15% sugar and oranges about 7%; neither fruit contains any starch. The sugar in fruit is usually a mixture of glucose and fructose. Fruits also contain a variety of organic acids, particularly citric, malic and tartaric acids. These acids are responsible for the sourness of unripe fruit. During ripening the concentration of these acids falls and that of sugar rises.
Vegetables have no common biological structure. They are usually classified according to the parts of the plants from which they come. Some vegetables may fall into more than one category when more than one part of the plant is eaten, e.g. both the roots and leaves of beetroot can be eaten.
6.3.1 Structure of a plant cell(A) cell wall (a very rigid outer wall which is thickened by cellulose, so the older the plant, the thicker the walls)(B) nucleus (control centre of the cell)(C) cytoplasm (a jelly-like substance that surrounds nucleus)(D) vacuole (storage area for the plant cell)(E) cell sap (inside the vacuole which is a watery solution of sugars, vitamins, pigments and mineral salts)
6.3 Vegetables
Fruit are seed-bearing parts of plants, during ripening they become fleshy, succulent and sweet.
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Figure 6.3 Structure of a plant cell
6.3.2 Nutritional Value of Vegetables They usually have high water content and, therefore, their contribution to the total energy of the diet is low. They are important in the diet because of their content of indigestible carbohydrate which provides dietary fibre. They are also good sources of vitamin C, carotene and minerals. Vegetables also contain potassium that helps to maintain healthy blood pressure.
6.3.3 Types of vegetables
(A) Leafy vegetable
(B) Flowers, buds and stalks
(C) Seeds and pods
(D) Fruit vegetables
(E) Roots, bulbs and tubers
(F) Fungi and algae
cell wall
chloroplast
cytoplasm
nucleus
vacuole
mitochondrion
cytoplasmic membrane
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Examples
Cabbage, Chinese cabbage, Ceylon spinach, Chinese box thorn (matrimony vine), Chinese dwarf white cabbage, Chinese flowering cabbage, Chinese kale, Chinese spinach, Chinese white cabbage, coriander (Chinese parsley), flat cabbage, garland chrysanthemum, head lettuce, lettuce, mustard cabbage (lead mustard), parsley, pea shoot, small Chinese white cabbage, spinach, Tientsin cabbage, water spinach, watercress
Flowers: broccoli, cauliflowersBuds: lily budStalks: asparagus, bamboo shoot, celery, chive, flowering chive, water dropwort (eater celery), wild rice shoot, yellow chive
Seeds: baby corn shoot, black sesame seed, broad bean, fresh soya bean, lotus seed, mung bean sprout, soya bean sprout, sunflower seed, sweet corn, white sesame seed, black bean, broad bean, brow bean, mung bean, peanut, red bean, red kidney bean, soya beanPods: French bean (snap bean), garden pea (snow pea), honey pea (sugar pea), string pea (green asparagus bean, green yard-long bean), white long bean (white yard-long bean)
Angled loofah (angled luffa, silky gourd), bell pepper (capsicum), bitter cucumber, bottle gourd, chayote, cucumber, egg plant (aubergine), hairy gourd (hairy melon, Chinese marrow, fuzzy melon), okra (lady’s finger), papaya, pumpkin, red chilli, red cluster pepper, smooth loofah (water gourd, sponge luffa, vegetable sponge), tomato, wax gourd (winter melon), yellow cucumber
Roots: beetroots (beet), carrot, green radish, kohlrabi, turnip (Chinese radish)Bulbs: garlic, onion, spring onionTubers: arrowhead, ginger, kudzu, leek, lotus root, potato, red budded taro, sweet potato, taro, water chestnut
Fungi: abalone mushroom, bamboo fungus, black fungus,button mushroom, fresh Chinese mushroom, golden mushroom, Hedgehog Hydrum mushroom, straw mushroom, white fungus, wood fungusAlgae: black moss, laver, sea weed
Different parts of plants
Leafy vegetable
Flowers, buds and stalks
Seeds and pods
Fruit vegetables
Roots, bulbs and tubers
Fungi and algae
Table 6.4 Different parts of plants
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(B) Types of meat (i) Red meat vs. White meat
Red meat is darker in colour when compared with white meat. The dark colour of red meat is due to a higher content of myoglobin, which is a protein responsible to carry oxygen in muscle cells. So that more active muscle contains higher content of myoglobin. Therefore, meat contains highly active muscle is darker in colour.
(ii) Meat cutsMeat carcasses are usually cut into different section for sale in butcher shop. Figure 6.8 and 6.9 are meat cutting chart for beef and pork respectively.
Figure 6.5 Structure of meat
6.4 Meat and their offals6.4.1 MeatMeat is a valuable protein food and an important source of vitamin B and iron. It is a poor source of calcium. Although liver and kidney contains vitamin A and D, meat does not. There is no significant difference in nutritional value between expensive and cheaper cuts of meat, or between fresh or frozen meat. Canned meats contain less thiamin than cooked and fresh meat. Some food such as sausages, ground beef and some fatty cuts of beef, pork and lamb are high in saturated fat that could increase low density lipo protein (LDL) cholesterol in blood. In addition, a high intake of fats may result in consuming more calories.
The composition of meat varies a lot. The fat content varies from 10% to 50%, depending on the animal and the part of animal from which the meat has come. Water content is inversely proportional to fat content, i.e. the meat with a high fat content has a low water content and vice versa.
(A) Structure of meat
Bone
Tendon EpimysiumEndomysium
Fascicle
Muscle fiber
Blood vesselPerimysium
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Figure 6.6 Meat cutting chart of beef
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Figure 6.7 Meat cutting chart of pork
Clear Plate
Back Fat
Boston Butt
Hand (or shoulder)
Spareribs Belly
Loin
Leg
Hind Feet (Pig’s Feet)
Jowl
BOSTON BUTTBlade SteakBlade Boston roast
LOINBlade chopSpateribsTop loin roastBlade loinRib chopLoin chopTenderloinCenter loinSirloin chopSirloin cutletSirloin
LEGHamCenter cut ham slice
HIND FEETPig’s feet
JOWLJowl
HAND(or shoulder)Picnic roastArm steakHock
SPARERIBSSpareribs
BELLYBacon
CUTS OF PORK
CUTS OF PORK
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6.5 Poultry
The term poultry is used for birds reared for their meat and/ or eggs and includes chickens, turkeys, ducks and geese. Poultry meat is similar in structures and composition to that of beef, lamb and pork except that chicken and turkey meat are much lower in fat.
6.6 Fish
There are many species of both freshwater and seawater fish used for human consumption. The connective tissue of fish contains collagen only without any of the tough elastin. This collagen is easily converted into gelatin during the cooking of fish. This explains why fish is more tender than meat and more easily cooked. The fat in fish is found entirely dispersed among the muscle fibres: there is no separate fatty tissue as there is in meat. The amount of minerals and extractives are much less than in meat and this accounts for their comparative lack of flavour. Well-made sauces, vinegar, pepper and salt are valuable aids in making fish more appetising.
(C) Meat analogueMeat analogue, also called meat substitute, which simulates the aesthetic qualities (e.g. texture, flavour and appearance) of certain kinds of meat. Generally, meat analogue is understood to be made from non-meat materials. The market for meat analogue includes both vegetarians and non-vegetarians, who avoid eating meat for some reason, but still wish to enjoy the taste of meat.
Some meat analogues are products of wheat gluten, rice, mushroom, legumes and pressed-tofu with flavouring added to make it tastes like chicken, beef or seafood. The most common meat analogue in the Western countries is textured vegetable protein (TVP), which is a dry bulk commodity derived from soya, soya concentrate, mycoprotein-base Quorn and modified defatted peanut flour.
(D) Derivatives of meatGelatin is a protein produced by partial hydrolysis of collagen extracted from the bones, connective tissues, organs, and some intestines of animals such as the cattle, and horses. Gelatin melts when heated and solidifies when cooled again. Together with water, it forms a semi-solid colloid gel. Gelatin forms a solution of high viscosity in water, which sets to a gel on cooling, which is commonly used to make jelly.
6.4.2 Offals Offal is the entrails and internal organs of a butchered animal. The word does not refer to a particular list of organs, but includes most internal organs other than muscles or bones. Examples of offals include tripe, omasum, heart, liver, lung, tongue, gizzard.
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The flesh i.e. the muscle of fish, is divided into flakes between bones. In some fish e.g. cod, the flakes are large and easily separated from bones, while in others e.g. herrings, they are small and difficult to remove. The proteins of the muscle fibres are similar to those of meat. They contain the essential amino-acids and are of high biological value.
6.6.1 Types of fish(A) Oily fishsuch as mackerel, salmon, sardines, herring and tuna, contain between 10% and 20 % unsaturated fat. These have the fat distributed through the flesh which is therefore darker in colour.
(B) White fish contain less than 2% fat they can be: (i) round fish e.g. cod, halibut(ii) flat fish e.g. plaice, sole turbot. These have all their fat stored in the liver, which is not usually eaten.
(C) Shellfish are classified into three basic categories: (i) crustaceans have horny outer-covering, e.g. shrimps, prawns, crabs and lobsters (ii) molluscs have hard shells, e.g. oysters, cockles and mussels.(iii) echinoderms, e.g. cuttlefish, squid
6.6.2 Nutritional Value of FishThe amount of fat in fish varies considerably with the types of fish and the time of the year. Herring, mackerel, pilchards and sardines contains up to 20%. The actual amount of fat in fish alters with the time of year because it depends upon the fish’s food and the nearness of spawning. Herrings contain most fat during the summer months when they are feeding intensively and least in spring and autumn when they are spawning. The salmon is at its best when it first leaves the sea to go upstream to breed. During the breeding season the fat is used up and the flesh becomes pale and watery.
The minerals in fish consist chiefly of calcium and phosphorus. These are provided in largest amount when we eat the bones of such fish as sardines. Seawater fish contain traces of iodine but there is little iron in fish except in sardines and sprats.
Oily fish contain fat soluble vitamins A and D. White fish contain only a small amount of vitamin A and no vitamin D at all except that stored up in the liver. Fish liver oil, particu-larly those of halibut and cod, contain exceptionally large amounts of both vitamins.
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6.7 Eggs
6.7.1 Hen’s EggsA hen’s egg weighs about 60g and is made up of three major parts: shell, white and yolk. The porous shell is composed mainly of calcium carbonate. The colour of the shell does not indicate the quality of the egg but depends on the breed of hen. Inside the shell two thin membranes separate shell from the white. The white is divided into regions of thick and thin white and accounts for about 60% of the total weight of an egg. The yolk is suspended in the white and is held in position by strands of protein called chalazae (Figure 6.8).
There are small amounts of the vitamin D in most fish; oily fish containing more than white. Oily fish are thus valuable body-building, energy and protective foods while white fish are body-building foods only.
6.6.3 Ways of Preserving Fish(A) Sun-dried fishStockfish is unsalted fish, especially cod, dried by sun and wind on wooden racks on the foreshore called flakes, or in special drying houses. The drying of food is the world’s oldest known preservation method, and dried fish has a storage life of several years. The method is cheap and effective in suitable climates, the work can be done by the fisherman and family, and the resulting product is easily transported to market. The fish is prepared immediately after capture. After gutting the fish, it is either dried whole, or split along the spine leaving the tail connected. The fish is hung on the flakes under cold condition. The cold climate protects the fish from insects and prevents bacterial growth. A temperature just above zero degrees Celsius, with little rain, is ideal.
(B) Salted fishOne of the oldest Cantonese preserved foods is salted fish. It is prepared by adding a large amount of salt onto fish and getting sun-dried. Salt inhibits the growth of micro-organisms by drawing water out of microbial cells through osmosis. Concentrations of salt up to 20% are required to kill most species of unwanted bacteria. The most common fish used for the preparation of salted fish is Thread Fin.
(C) Smoked fishSmoking, often used in preservation of fish or meat, adds chemicals to the surface of meat that reduce the concentration of salt required.
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The white of an egg is basically a colloidal solution of protein (mainly albumin) in water, together with small quantities of vitamins and minerals. The yolk is an oil-in-water emulsion and is approximately one-third fat, one-half water and one-sixth protein. The yolk also contains vitamins and mineral salts.
The nutritive value is high, but it is not a complete food for humans. Eggs are normally considered as protein foods but they also provide substantial quantities of iron, vitamin A and D, and riboflavin. They provide smaller amounts of other vitamin B. Eggs contain saturated fat and cholesterol, therefore they are not recommended to be consumed in large numbers for people at risk from coronary heart disease.
Besides hen’s eggs, there are duck eggs, goose eggs, quail eggs and ostrich eggs that are commonly consumed by humans.
Figure 6.8 Structure of a hen’s egg
6.7.2 Preserved eggs(A) Chinese salted duck eggsThe Chinese salted duck eggs are made by immersing duck eggs in brine, or coating them individually with a paste of salt and mud or clay. The eggs stop absorbing salt after about a month, having reached chemical equilibrium. Their yolks become an orange-red coloured solid, but the white remains liquid. They are boiled before consumption.
(B) Century eggsA century egg or thousand-year-old egg is preserved by fermenting an egg in a mixture of clay, wood ash, salt, lime, and rice straw for several weeks to several months, depending on the method of processing. After the process is completed, the yolk becomes a dark green, cream-like substance with a strong odour of sulfur and ammonia, while the white becomes a dark brown, transparent jelly with a comparatively mild, distinct flavour. The transforming agent in a century egg is the alkaline material, in the mixture which gradually raises the pH of the egg from around 9 to 12 or more. This chemical process causes an “inorganic version” of fermentation, which breaks down some of the complex, odorless proteins and fats of the yolk into simpler, flavoured compounds.
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6.8 Dairy productsDairy products are best for teeth and bones as they are rich in calcium, protein, vitamin D and vitamin B complex. So, diets rich in milk and dairy products help to build and maintain bone mass and reduce the risk of osteoporosis. Diets that include adequate dairy products are regarded as having a better overall nutritional quality.
Calcium is one of the main minerals that can be found in sufficient amount in milk and dairy products. It is used for building bones and teeth and in maintaining bone mass. Dairy products, especially yoghurt and fluid milk, provide potassium which may help to maintain healthy blood pressure. Milk is usually fortified with vitamin D that helps in maintaining proper levels of calcium and phosphorous in building and maintaining bones.
6.8.1 MilkMilk is composed of a variety of nutrients either dissolved in water or dispersed in the form of a colloid. The colloidal system is complex but is basically an oil-in-water emulsion.
Milk, being a complete food for young calves, is of high nutritional value. It is a valuable source of protein, riboflavin and calcium and provides a sufficient quantity of other vitamin B and vitamin A. However, it is not a complete food for humans as it is relatively deficient in iron, vitamin C and vitamin D. An increasing proportion of people consume low fat milk, i.e. skimmed milk. Choosing low fat milk is a useful way of reducing saturated fat intake while maintaining intake of protein, calcium and vitamin B.
6.8.2 CheeseIn some respect, cheese can be thought of as a concentrated form of milk (1 litre of milk produces ~100 grams of cheese). However, unlike milk, cheese does not contain carbohydrate; the lactose is partly converted into lactic acid and the remainder is lost in the whey.
Since cheese has a lower water content than milk it is a more concentrated source of nutrients. Cheese is particularly rich in calcium and is a good source of protein, vitamin A and riboflavin. It also provides plenty amount of other vitamin B and D but contains no vitamin C and is a relatively poor source of iron.
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Types
Soft Cheese
Semi-soft cheese
Semi-hard cheese
Hard cheese
Blue cheese
Processed cheese
Characteristics
This type of cheese does not undergo any heating or pressing. A penicillium fungus gives it its furry white rind. Not usually used in cooking, soft cheeses are used to spread on bread or crackers.
This type of cheese does not undergo any heating or pressing. The rind is rinsed and brushed with a solution of salted water enriched with specific bacteria, which encourages orange-coloured fungi to appear. Ideal for snacking or desserts, some semi-soft cheeses may be used for cooking if they stand up to heat well enough.
Once transformed into curds, these types of cheese are heated, pressed, moulded and left to ferment. This is how the famous holes appear in cheese that is stored in cellars (such as Emmental). They are very rich in calcium. Maturing can take from three to nine months, or even longer.
A hard cheese needs to have less water content (30-48%) in the end product than a soft cheese (which has 50-70%). Packed into moulds, firmly pressed and stored for long periods (up to two years), they become hard and more pungent over time.
The production of this cheese involves inoculating it with fine, long skewers containing penicillium cultures which allow mould to develop in the cheese. This is what produces the green or blue veins.
The cheese is made up of a mixture of cheese(s), butter, cream and milk that is heated and emulsified. Some varieties are flavoured or spiced. The shelf-life is generally very long.
Examples
Brie, Camembert, Feta
Munster, Port Salut, Gouda
Cantal, Cheddar, Cheshire, Comté, Edam, Emmental, Gloucester, Gruyère, Lancashire, Red Leicester, Wensleydale
Aged Manchego, Mimolette, Parmesan
Roquefort, Gorgonzola, Stilton
Table 6.9 Types of cheese
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6.8.3 CreamCream is a dairy product that is composed of the upper-butterfat layer skimmed from the top of milk before homogenisation. In un-homogenised milk, over time, the lighter fat rises to the top. In the industrial production of cream this process is accelerated by using centrifuges called “separators”. In many countries, cream is sold in several grades depending on total butterfat content. Cream can be dried to a powder for shipment to distant markets.
Cream is used as an ingredient in many foods, including ice cream, many sauces, soups, and some custard bases, and is also used for cakes. Irish cream is an alcoholic liqueur which blends cream with whiskey and coffee. Cream is also used in curries such as masala dishes. Cream (usually light cream/half-and-half/single cream) is often added to coffee.
For cooking purposes, both single and double cream can be used in cooking, although the former can be separated when heated, usually if there is a high acid content. Most United Kingdom (UK) chefs always use double cream or full-fat crème fraîche for a hot sauce, to prevent any problem with it separating or “splitting”. In sweet and savoury custards such as those found in flan fillings, crème brûlées and crème caramels, both types of cream are called for in different recipes depending on how rich a result is called for. It is useful to note that double cream can also be thinned down with water to make an approximation of single cream if necessary.
Characteristics
Cream that has been slowly heated to dry and thicken it, producing a very high-fat (55%) product
Very rich, with a fat content of 48 per cent, making it the most versatile cream because it withstands boiling, whips and freezes well
A lighter version of double cream with a fat content of over 35 per cent
made by whisking or mixing air into cream with more than 30% fat, to turn the liquid cream into a soft solid
Mixtures of cream and water or cream and milk
Major uses
Served with scones and jam
The easiest and thickest for puddings and desserts
Whips well but lighter
For decoration of desserts
Only used in coffee
Name
Clotted cream
Double cream
Whipping cream
Whipped cream
Half cream
Table 6.10 Types of cream
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6.8.4 YoghurtYoghurt is made by souring milk, using a pure culture of bacteria. The two species of bacteria normally used are Lactobacillus bulgaricus and Streptococcus thermophilus. They convert the lactose in milk into lactic acid which together with a variety of minor products is responsible for the flavour of yoghurt. The acid also brings about coagulation of the milk proteins and helps to preserve the product.
Since it is made from milk, the composition and nutritive value of yoghurt are similar to milk. Low fat yoghurt is produced from skimmed milk. Fruit yoghurts are normally higher in carbohydrate as they contain fruits and also usually contain added sugar.
6.8.5 Butter and MargarineButter is made from milk, which is first separated into cream and skimmed milk. It is made by churning cream to remove the liquid buttermilk. It contains not less than 80% milk fat, with vitamins A and D, and the rest is water. Butter is high in saturated fat and should be used sparingly in a healthy diet. Butter has a good flavour, which makes it delicious to eat with bread, and to use for making cakes, biscuits and pastries.
Margarine can be made from vegetable fat or a mixture of animal and vegetable fat, which are hardened by the addition of hydrogen gas – a process called hydrogenation. This process makes the fat more saturated, which helps the product to keep longer. Margarine was first developed as a substitute for butter. Today it is used for cakes, biscuits and pastries. Margarine for cakes and biscuits is soft for creaming. Pastry margarine is hard, with a high melting-point. Table margarine is blended to have a spreading consistency.
Characteristics
Single cream needs to be homogenised to prevent separation, because of its relatively low fat content of 18%
Major uses
Single cream will not whip, but can be used for pouring over fruit or in coffee, and for adding to casseroles and soups
Name
Single Cream
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6.9 Soya Bean and Soya Bean products
Soya bean sproutsThey can be served hot or cold in savoury dishes
Soya milk(i) It can be served hot or cold, sweet or savoury(ii) The sweet soya milk can be flavoured e.g. coconut flavoured, soya milk(iii) It can be obtained fresh, in bottles, in paper cartons and in packets; or in dehydrated form(iv) Soya milk powder is a good substitute for cow’s milk. It is suitable for babies who are allergic to cow’s milk
Bean curd custard It can be served hot or cold, sweet or savoury
Bean curds(i) Soft bean curd (ii) Firm bean curd (iii) Bean curd in muslin (iv) Pressed bean curd - plain or spicy(v) Fried bean curd in cubes or cakes (vi) Bean curd puff
(A)
(B)
(C)
(D)
6.9.1 Nutritive value of soya beans
(A) Protein - 39.2%(i) a high protein content which is similar to that of meat(ii) contains a maximum proportion of amino acids essential in the diet
(B) Carbohydrates - 24.1%(i) contains little starch(ii) good for diabetics and starch-restricted diets
(C) Fat - 18.7%(i) the fatty acids present are easily digested.(ii) suitable in the diet of people who have heart disease or who are overweight
(D) Vitamins & Minerals - 4.6%rich in calcium, phosphorus, iron, vitamins A and B
(E) Water - 13.4%
6.9.2 Soya bean products
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Food Commodities
Fermented bean curd(i) White fermented bean curd(ii) Red fermented bean curd (iii) Shrimp-roe flavoured fermented bean curd (iv) Chili flavoured fermented bean curd
Bean curd sheets(i) Bean curd sheet (ii) Fresh bean curd sheet (iii) Bean curd skin (iv) Bean curd sticks (v) Bean curd strips
Preserved bean and paste(i) Soya bean paste (ii) Hot bean paste (iii) Sweet bean paste (iv) Yellow bean paste
Soya sauce(i) Light soya sauce (ii) Dark soya sauce (iii) Straw mushroom flavoured soya sauce (iv) Shrimp-roe flavoured soya sauce (v) Chili soya sauce
Soya bean flourIt can be used as seasoning
Soya bean oil It can be used for cooking in both sweet and savoury dishes
Ready to serve(i) Vegetarian sausage (ii) Vegetarian chicken (iii) Vegetarian duck (iv) Vegetarian goose (v) Vegetarian ham (vi) Pressed bean curd in floral-cut
Texture Vegetable Protein (T.V.P.)It is a kind of food made mainly from soya protein, with some wheat and other vegetable or cereal protein. The term “textured” refers to the process which forms the protein powders into granules, chunks, flakes or fibres.
(E)
(F)
(G)
(H)
(I)
(J)
(K)
(L)
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6.10 Sugars (honey)Sugar is an important source of energy to the body, and are relatively quickly digested and absorbed. Sugar, in the form of sucrose, can be made from sugar beet or sugar cane. The beet or cane is crushed and mixed with water and the liquid is extracted and boiled to obtain sugar crystals.
An excess of sugar in the diet is undesirable because it can lead to tooth decay. Alternatives such as fruit purees and artificial sweeteners can be used for sweetening food products. Artificial sweeteners such as saccharin provide the body with very little energy.
Honey is produced by bees from the nectar obtained from flowers. It is a form of invert sugar (i.e. a mixture of glucose and fructose). The nectar is mostly sucrose and this is changed by a process called inversion into invert sugar. This happens as the nectar moves through the bee’s body.
Honey attracts water and keeps products moist, which makes it useful in baking. It also has a very appealing flavour.
6.10.1 Types of sugarThere are many varieties of sugar. They are identified by the size of the sugar crystals and by the colour.(A) Granulated sugar is white and is a all-purpose sugar. (B) Castor sugar is white and is finer than granulated sugar. It is used for cake and biscuit making(C) Icing sugar is a fine sugary powder and is used for icings and sweets(D) Brown sugars have a stronger flavour than white sugars and are used for gingerbreads and biscuits(E) Cube sugar is usually white, but brown cube sugar is becoming popular. It is made from moist granulated sugar, which is put into moulds, dried and cut into cubes.
6.10.2 Uses of sugar in food preparationSugar has other uses than that of sweetening food, e.g.
(A) It is an essential ingredient in sweets, toffees, fudges and cake decorations(B) It improves the colour of baked foods such as cakes, biscuits and (the brown crust of) bread(C) It acts as a preservative in jams and marmalades(D) It helps cakes to be moist(E) It assists fat in incorporating air in cake mixtures(F) It strengthens proteins in whisked eggs
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6.11.1 Types of fatty acidsThere are three main types of fatty acid: saturated, mono-unsaturated and polyunsaturated. Animal fats are mainly saturated. Plant oils are mainly unsaturated.
(A) Saturated fatsSaturated fats are found largely in meat and dairy products as well as coconut and palm oil. Saturated fats are usually solid at room temperature, and they are more stable, that is, they don’t combine readily with oxygen and turn rancid, e.g. butter and shortening. Solid fats come from many animal foods and can be made from vegetable oils through a process called hydrogenation as a result of the formation of trans fat. French fries, donuts, biscuits, chips and other snack foods are high in trans fatty acids. In fact, nearly all fried or baked goods have some trans fats. Saturated fatty acids increase blood cholesterol thereby increasing the risk of coronary heart disease and stroke.
(B) Monounsaturated fatsMonounsaturated fats are typically high in vitamin E and are found in canola oils, olives, olive oil, nuts, peanut oil, and avocados. Monounsaturated oils are liquid at room temperature but start to solidify at refrigerator temperatures. Monounsaturated fatty acids can lower blood cholesterol when substituted for saturated fats.
(C) Polyunsaturated fatsPolyunsaturated fats come from plants and fish. The best sources are oily fish, walnuts, sesame and pumpkin seeds. Polyunsaturated fatty acids come mainly from seed oils. Polyunsaturated fats, which contain mostly polyunsaturated fatty acids, are liquid at room temperature and in the refrigerator. These fats are extremely unstable and easily
6.11 Cooking fats and oilsFor maintaining a balanced diet, other than obtaining sufficient nutrients from different food sources, we should also try to reduce fat intake. When we eat fats and oils, we consume fatty acids. Essential fatty acids play a vital role in the functioning of the human body.
6.10.3 Examples of food with high sugar content (A) Cakes(B) Sweet Pies(C) Cookies(D) Soft drinks(E) Fruit drinks(F) Honey(G) Syrup
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6.12 Food composition table The nutritive value of foods can be found from the food composition table. A food composition table is a compilation which lists the nutritive values of foods. Each food items are classified into different food categories. The following page is the example of a common food composition table (Table 6.11):
combine with oxygen in the air to become rancid. Polyunsaturated fatty acids help lower total blood cholesterol when substituted for saturated fats.
To reduce excessive intake of fats and oils, we should choose healthy cooking methods. Cooking methods that use small amount of oil such as steaming, stewing, simmering, boiling and scalding should be used more often. The core principle of cooking is to avoid frying and deep-frying. In addition, we should also remove visible fat from meat before cooking.
(D) Fats vs. OilsFats are lipid which is in solid form under normal room temperature and pressure, while oils are lipid which is in liquid from under normal temperature and pressure.
(E) Animal LipidAnimal lipids are often claimed to be less healthy than plant oil owing to their association with high cholesterol and saturated fatty acids content. Consumption of animal fat has been linked to elevated blood cholesterol, which leads to heart diseases. Examples of animal fat are cod liver oil, lard, beef tallow, butter, chicken fat, etc.
(F) Vegetable lipidVegetable oils are theoretically healthier than animal lipid as they do not contain cholesterol. Vegetables oils are often extracted from seeds of oilseed plants. Oils extracted from plants have been used in many cultures (e.g. China, Greek), since ancient time. Generally, plant oil contains more unsaturated fatty acids than animal lipid. Common examples of vegetable oils are canola, olive, peanut and corn oil.
6.11.2 Examples of food with high fats and oil content
(A) Margarine
(B) Salad dressing
(C) Mayonnaise
(D) Cream Cheese
(E) Sauces
(F) French Fries
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Foo
d Ite
m
BIS
CU
IT, A
NZ
AC
BIS
CU
IT, B
RA
N
BIS
CU
IT, C
HO
CO
LAT
E
BIS
CU
IT, C
HO
CO
LAT
E C
HIP
BIS
CU
IT, C
HO
CO
LAT
E C
HIP
an
d N
UT
BIS
CU
IT, C
HO
CO
LAT
E-
CO
AT
ED
BIS
CU
IT, C
RE
AM
- an
d JA
M-F
ILLE
D
BIS
CU
IT, C
RE
AM
-FIL
LED
BIS
CU
IT, C
RE
AM
-FIL
LED
, C
HO
CO
LAT
E
BIS
CU
IT, C
RE
AM
-FIL
LED
, C
HO
CO
LAT
E-C
OA
TE
D
F
ood
Item
BIS
CU
IT, C
RE
AM
-FIL
LED
, W
AF
ER
BIS
CU
IT, F
RU
IT
BIS
CU
IT, F
RU
IT a
nd N
UT
BIS
CU
IT, F
RU
IT, I
CE
D
BIS
CU
IT, F
RU
IT-F
ILLE
D
BIS
CU
IT, G
ING
ER
BIS
CU
IT, I
CE
D
BIS
CU
IT, J
AM
-FIL
LED
BIS
CU
IT, M
AC
AR
OO
N,
CO
CO
NU
T
BIS
CU
IT, M
AR
SH
MA
LLO
W
Por
tion
100g
100g
100g
100g
100g
100g
100g
100g
100g
100g
Por
tion
100g
100g
100g
100g
100g
100g
100g
100g
100g
100g
Ene
rgy
(Kca
l)
470
449
444
507
499
482
489
495
471
514
Ene
rgy
(Kca
l)
532
474
490
500
378
415
427
435
485
410
Pro
tein
(g)
6.2
6.6
6.2
6.3
6.5
6.5
4.2
4.9
5.7
5.9
Pro
tein
(g)
4.4
5.5 6 6.6
4.8
4.9
5.4
4.4
5.1
4.8
Car
bo-
hydr
ate
(g)
56.9
54.6
65.3
65.7
56.2
59.6
65.2
64.1
62.9
58.1
*Car
bo-
hydr
ate
(g)
65.3
63.4
58 64.1
68.6
68.7
72.4
64.6
58.4
62.6
Tota
l F
at (g)
24.1
22.6
17.2
24 27.4
24 23.3
24.1
21.6
28.7
Tota
l F
at (g)
28 21.9
25.8
23.9
9.9
13.3
12.8
17.7
25.6
15.8
Sat
urat
ed
Fat (g)
15.5
12.8
7.9
12.6
13.5
14.5
13.6
15.3
12.7
18.5
Sat
urat
edF
at (g)
18.2
11.2
13 15.4
4.3
6.3
5.6
8.7
18.2
9.7
Cho
lest
erol
(mg)
18 47 15 15 25 14 24 23 14 14
Cho
lest
erol
(mg)
19 24 33 30 12 11 16 18 10 11
Die
tary
F
ibre
(g)
3.6
10.6
1.9
1.9
2.4
1.4
1.5
1.5
1.5
0.6
*Die
tary
F
ibre
(g)
1.4
2.4
1.9
1.9
2.8
1.9
1.5
1.8
8.7
1.8
Sug
ar(g
)
26.1
27.6
23.9
28.1
25 27.7
33.5
31.4
30.8
38.9
Sug
ar(g
)
38 25.5
24.8
31.9
38.6
33.2
40.3
32.4
35.5
35.9
Cal
cium
(mg)
63 49 40 53 114
68 27 63 52 135
Cal
cium
(mg)
52 43 74 94 39 88 28 34 21 26
Cop
per
(mg)
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Cop
per
(mg)
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Iron
(mg)
2.7
2.8
1.8
1.9
1.8
2.5
0.9
0.9
0.9
1.8
Iron
(mg)
1.1
1.6
1.6
1.7
2.5
1.9 1 1 1.3
1.2
Mag
nesi
um(m
g)
41 66 24 19 33 39 14 14 25 29
Mag
nesi
um(m
g)
14 20 24 17 23 21 12 15 22 17
Pho
spho
rus
(mg)
144
285
152
119
215
156
66 118
107
144
Pho
spho
rus
(mg)
88 90 99 133
95 98 79 104
109
63
Pot
assi
um(m
g)
235
275
127
132
157
178
85 120
135
235
Pot
assi
um(m
g)
91 147
205
184
305
230
73 121
200
113
Sod
ium
(mg)
235
415
310
340
345
250
210
405
325
190
Sod
ium
(mg)
101
390
440
410
160
360
245
140
235
132
Table 6.11 Common Food Composition Table
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Food Commodities
6.12.1 What information can you find in a food composition table?
(A) Measures and weightsThe approximate measure given for each food is in cups, ounces, pounds, some other well-known unit (e.g. grams, millilitres), or a piece of a specified size. The measures do not necessarily represent a serving, but the unit given may be used to calculate a variety of serving sizes. For example, nutrient values of apple sauce are based on 1 cup (i.e. 250 ml) of apple sauce. If the serving you consume is 1/2 cup (i.e. 125 ml), the nutrients you have obtained should be the nutrient values listed in the composition table divided by 2 or multiply by 0.5.
(B) Food valuesIn a food composition table you can find out the energy value and the amount of different components in a food item, such as water content, carbohydrates, protein, fats, dietary fibre, vitamins and minerals. Water content is included because the percentage of moisture is necessary for identification and comparison of many food items. For example, to identify whether the coffee listed is powder or roasted raw bean, you could check the water value. There is much less water concentration in coffee powder.
Food energy is reported as calories. A calorie is the unit of measuring the amount of energy that protein, fat, and carbohydrate furnish the body. Alcohol also contributes to the calorie content of alcoholic beverages. The official unit of measurement for food energy is actually kilocalories (kcal), but the term “calories” is commonly used instead. In fact, “calories” is used on the food label.
(C) Using food composition table to compare different foods:When you are going to compare the nutritive value of 2 foods, you can use a food composition table. To check the nutritive value of a food, you should be able to identify some characteristics of a food, such as the food name, cooking method and weight.
(i) Food name and Brand name
You need to know the exact name of a food. For example, beef may come from different parts of cattle, you should be able to identify it, such as sirloin, flank, ribs.
(ii) Cooking method
Cooking method is one of the keys that affect the calories and nutritional quality of a food. Food cooked with frying generally has higher calories than those cooked with boiling.
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(iii) Unit conversion
= 0.035 oz
= 0.001 g
= 28.35 g (~28g)
= 16 oz
= 2.21 lb
= 100 g
= 1000 mg
= 1000 μg
= 453.59 g
= 1000 g
= 3.52 oz
Weight Measures
1 g
1 mg
1 oz
1 lb
1 kg
0.1 kg
= 1/3 Tablespoon
= 1 Tablespoon
= 1/8 cup
= 1 cup
= 0.034 fluid oz.
= 34 fluid oz.
= 2 cups
= 2 pint
= 4 quart
= 1.057 quarts
= 1/6 fluid oz.
= 1/2fluid oz.
= 1 fluid oz.
= 8 fluid oz.
= 1 cc
= 1000 ml
= 0.473 litre
= 0.946 litre
= 3.785 litre
= 0.264 gallon
= 4.9 ml
= 14.8 ml
= 29.6 ml
= 236.6 ml
= 0.001 litre
= 473 ml
= 946 ml
= 3785 ml
= 1000 ml
Volume Measures
1 teaspoon
3 tablespoon
2 Tablespoon
16 Tablespoon
1 ml
1 litre
1 pint
1 quart
1 gallon
1 litre
Table 6.12 Conversion table
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Comparing 2 foods with the help of food composition tableExamples: Food 1: Peanut, roasted, salted, without skin Food 2: Peanut, raw, with skin
Water
1.7 g
Water
4.8 g
Energy
2661 kJ
Energy
2376 kJ
Protein
25.1
Protein
24.7
Total Fat
52.7
Total Fat
47.1
Carbo-hydrates
14.1
Carbo-hydrates
8.9
Fibre
6.2
Fibre
8.2
Chole-sterol
0
Chole-sterol
0
Vit. A
0
Vit. A
0
Vit. C
0
Vit. C
0
Vit. E
1.37 mg
Vit. E
8.8 mg
Sodium
335 mg
Sodium
1 mg
Calcium
40 mg
Calcium
54 mg
Iron
1.2 mg
Iron
2.3 mg
By comparing the 2 sets of nutritive values, you will know that raw peanut is more nutritive than salted and roasted peanut. Raw peanut contains higher amount of dietary fibre, vitamin E, calcium and iron content, but lower in energy, fat and sodium content. It can be concluded that raw peanuts have higher nutritive value than salted and roasted peanuts.
(D) Daily intake In a food composition table, you can find the nutrient contents of each food. For example, raw peanuts contain 54 mg calcium. So what is the meaning of this number? Does it mean that the larger the number, the more nutritive the food is? The answer is no. Each nutrient has its own daily intake requirement. A daily intake is lower or higher than this requirement may have adverse effects to our body. For example, intake of vitamin A should not be less than 500 μg per day for adult women. An intake less than this amount may result in night blindness. In contrast, intake of vitamin A should not exceed 3000μg per day for adult women. Otherwise, toxicity may result. The requirements for each nutrient needed by our body are different. This requirement is called Dietary Reference Intakes (DRI).
Table 6.13 Nutrient content of Food 1 (Peanut, roasted, salted, without skin) (100g)
Table 6.14 Nutrient content of Food 2 (Peanut, raw, with skin) (100g)
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(i)
(ii)
Dietary Reference Intakes (DRI) is a set of values for dietary nutrient intake of healthy people in United States and Canada. These values are used for planning and assessing diets.
DRI is composed of 4 sets of values: Estimated Average Requirement, Recommended Dietary Allowances, Adequate Intakes and Tolerable Upper Intake Levels.
Estimated Average Requirement (EAR) is the amount of a nutrient that will maintain normal body function in 50% of people.
Recommended Dietary Allowance (RDA) is the average daily amount of a nutrient which is enough to meet the needs of nearly all healthy people. In simple words, it is a goal for dietary intake by individuals.
Adequate intake (AI) is the average amount of a nutrient that appears sufficient for people. This is a value used as a guide for nutrient intake when a RDA cannot be determined. For some nutrients, there is insufficient scientific evidence to determine EAR or RDA, in this case AI is used instead.
Tolerable Upper Intake Level is the maximum amount of a nutrient that is safe for most healthy people, higher than this level will increase risk of adverse health effects.
Figure 6.15 A simplified diagram illustrates the difference between 4 values.
(iii)
(iv)
(v)
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Nutrients
Vitamin A
Vitamin C
Vitamin D
Vitamin K
Vitamin B1
Vitamin B6
Vitamin E
Calcium
Chloride
Choline
Copper
Folate
Iodine
Iron
Sodium
Zinc
EAR
2083
75
--
--
1.0
1.1
12
--
--
--
700
320
95
6
9.4
RDA
3000
90
200
120
1.2
1.3
15
1000
2300
550
900
400
150
8
1500
11
TUIL
10000
2000
2000
--
--
100
1000
2500
3600
3500
10000
1000
1100
45
2300
40
Unit
IU
Mg
IU
μg
Mg
Mg
IU
Mg
Mg
Mg
μg
μg
μg
Mg
Mg
Mg
Table 6.16 Shows the value of EAR, RDA and TUIL of common nutrients
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Not for SaleThe copyright of the materials in this booklet belongs to the Education Bureau. The materials can be used by schools only for educational purpose. Written prior permission of the Education Bureau must be sought for other commercial uses.
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Family and LifeStyle
