2009 Nutritive aspects of foods (A)

2009 Nutritive aspects of foods (A) - Nutritive Aspects of...

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Nutritive Aspects of Foods (Part 1)
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Foods as conveyers of nutrients Protein Essential amino acids 9 Non-essential amino acids 11 Lipids Essential fatty acids 2 Vitamins Water-soluble 8 Fat-soluble 4 Minerals 12 Trace elements 7 Fiber Water Calories
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A “complete” protein : Contains all essential amino acids in amounts and proportions needed to maintain life and support growth when consumed as the sole source of protein * The biological value of proteins is commonly assessed using animal growth studies or nitrogen retention Measures of protein quality: Protein Efficiency Ratio Net Protein Utilization Biological Value
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Protein Efficiency Ratio = weight gain (g) (PER) __________ food consumed (g) [ Adolescent rats, 28 days, 10% protein diet ] Biological Value = retained nitrogen _____________ absorbed nitrogen [ Rats or humans ]
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gelatin
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Exception: Gelatin Limiting amounts of 4 amino acids (lacks tryptophan entirely ) Animal proteins Generally high biological value Plant proteins Generally lower biological value than animal proteins Reason: limited amounts of some amino acids: Wheat, rice: lysine Corn (maize): lysine, tryptophan Legumes: methionine
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[ Amino acid scores of 0.7 and below are considered inadequate ] Amino acid scores (1.0 = reference) Comparison of biological value and amino acid scores of some common protein-rich foods
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The most commonly or regularly eaten food, and which forms the mainstay of the total calorie supply, especially in poorer populations at times of food shortage Staple foods
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[ Opaque-2 maize: incr. lysine, tryptophan content ] Complementary proteins Ex.: corn (maize) black beans 100% beans 100% corn 50% beans 50% corn
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Essential fatty acids Linoleic acid 18:2 n-6 ( ϖ -6) Linolenic acid 18:3 n-3 ( ϖ -3) * ? Docosahexaenoic acid 22:6 n-3 ( ϖ -3) 18:3 n-3 22:6 n-3 Inefficient conversion in humans * plants fish
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2009 Nutritive aspects of foods (A) - Nutritive Aspects of...

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