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Nutrition and Dietetics
NUTR 214
Louise Thibault

Food Composition – Lecture 1 and Chapter 3 - Food: substance that provides energy and nutrients. We eat foods, not nutrients - 1 calorie = 42 kilijoules Nutrients - Essential for life, must be consumed in diet to live, grow and reproduce - ~44-47 nutrients essential for humans - Most foods are combinations of nutrients o Exceptions: oil is 100% lipid; table sugar is 100% CHO - Ex: bread’s structure is due to formation of gluten (protein formed by mixing and kneading dough) o Gluten in flour form is glutenin and gleitin. Combined with water = sticky and elastic. In oven, expand and makes bread - Ex: clear raw egg turns white b/c protein structure changes - Ex: Cake rises due to CO2 from baking soda - Ex: Meat turns brown when cooked due to maillard reaction - Ex: beating heavy cream creates stable foam of whipped cream  protein has property of foaming Major Classes of Nutrients - 6 nutrient groups: carbs, protein, fat, water, mineral, vitamins - Components that nourish the body and brain for growth, maintenance, repair - Food usually has all these components, invarying amounts - Humans: 60-70% water, 15-25% fat (varies), 15% protein, 12% minerals o We have vitamins and carbs, but they’re not main components that make up body o Carbs important part still, b/c energy, but when not used, they’re stored as fat. Carbohydrates - Monosaccharide o Hexoses (6C) for Energy:  Glucose: found in food and in blood (blood sugar)  Fructose: fruit, high fructose in corn syrup. Is the sweetest  Galactose: in milk and milk products o Pentoses (5C) for DNA: ribose, arabinose - Disaccharide: o Sucrose: glucose + fructose. Most predominant in disaccharide  Table sugar, fruits, vegetables o Maltose: found in beer. Also in starch o Lactose: milk and milk products - Oligosaccharides: few monosaccharides linked together  not very common in foods o In dried beans, not well digested in human digestive tract o Digested by intestinal bacteria = gas as by product o Food industry uses: for bulking agents in low-calorie diet foods (drinks, yoghurt) o Are not cariogenic (cavity producing) - Polysaccharide o Digestible: Plant Starch (Amylose, amylopectin), Animal Starch (glycogen)  Many Glu units joined together in straight chain (amylose) or branched chain (amylopectin).  Ex: corn, wheat, potato starch o Indigestible: Fiber (cellulose, hemicellulose, pectin, gums, inulin)  Many Glu units but linkages cannot be broken down  Fiber v. imp in our diet b/c associated with bowel regulation and prevention of heart disease  Helps retain water in colon to make stool after  Soluble fiber seen with decreasing cholesterol  Also keeps blood sugar @ certain levels o For every 1 gram of Crude fiber, there is 2-3 grams of dietary fiber  Crude fiber is measured by treating food with strong acid (like stomach) then strong base (like intestines). Measure what is left over.  Dietary Fiber is measured by association of official analytical chemists intern’l - Role of Carbs (except fiber): o Primary function is to provide body with energy: 4kcal/g o CHO’s converted to glucose, which can be used by all parts of body o Also required to create essential compounds and other substances - Alcohol: 7kcal/gram Lipids - Fats found in foods: coconut, nuts and seeds, avocado o Triglycerides: 95% of lipids acquired from diet (Acyl = ester, so should be called triacylglycerol) o Sterol: cholesterol, phytosterol (can decrease blood cholesterol) o Phospholipids: lecithin, similar to triglycerides b/c FA chains  Phosphate head = polar. Eggs have lecithin = emulsion o Plant foods usually 85:15 of Polyunsaturated:Saturated fats o Animal foods usually 50:50 - Provides energy  9kcal/g (>2x CHO) - Essential fatty acids (EFA)  linoleic and linolenic acids o Lack of EFA = dermatitis and retards growth (babies and children!) - Needed to create essential compounds: o Cholesterol, hormones, sex hormones, vitamin D - Deposition of fat around organs to protect, under skin to retard heat loss from body - In foods, carriers for fat-soluble vitamins - Contributes to satiety: delays time that food leaves stomach = better digest Protein - Long chains of AA - Some AA essential (in diet b/c we cannot synthesize or not enough) - High vs Poor Quality: o (Complete)High qual = high levels of essential AA in correct ratios o (Incomplete)Poor qual = lower amounts and ratios of essential AA o Complementation: pairing of foods to supply missing AA in each other  Mostly legumes (beans, lentils, peas) with grains - Primary function to build and repair body tissue - Antibodies - Water and pH balance - Transport of substances - Also energy  4kcal/g Water - Hydration and transport of nutrients  assimilating, digesting, absorbing, transporting, metabolizing, excreting all rely on water - Dilution of toxins (to excrete through urine) - Maintenance of body temperature (high heat capacity) - Obtained from: Liquids, Foods, Metabolism (requires liquid or food). Lettuce and tomatoes have high water content (95%) o Foods high in water are low in energy and fat - Minerals in water can make water “hard”  more calcium carbonate - Water ensures even distribution of heat but needs more E - Moist heat cooking methods: boiling, simmering, steaming, stewing, braising - Colloidal Dispersion: when particles are not truly dissolved in solvent o Salad dressing (liquid in another liquid), jam, gelatin, whipped cream o Suspension: Water and Cornstarch o Emulsion: water in oil or oil in water (w/o and o/w). Neither dissolve but dispersed - If remove water from food, will preserve food o Food’s water availability determines perishability  bacteria need water to grow o Food with high water content = more perishable Vitamins - Organic (C) found in plant and animal tissue - Generally cannot be synthesized; obtained from food - Needed to perform metabolic and regulatory functions (activates coenzymes) - Body can’t distinguish between natural or synthetic - Synthetic used to enrich: milk, fruits drink, margarine, bread, cereal - Enriched: originally present in food but lost through processing, and put back - Fortified: not originally present in food but added Minerals - Inorganic, leaves ash when burned - Macrominerals: Ca, P, Mg, S, Na, K, Cl - Trace Minerals: Fe, I, Zn, Cu, Mn, Se, Mb, F, Cr, Co o Hg and Al can get into body  but are nonnutritive, is
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