Food Composition - NUFS100 Topic 2 PDF
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Uploaded by CalmFable4793
University of Alberta
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Summary
This document provides an overview of food composition, covering various aspects like the chemical makeup of nutrients, their functions and importance. It details techniques for calculation, and relationships between various components. Suitable for an undergraduate level food science course.
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Food composition Recall:food products come from agri-food systems - From farm gate to consumers plate - Composed of plant/animal cells Overview: - Food is a made up of portions of carbohydrates, proteins, water, fat, and vitamins and minerals - ...
Food composition Recall:food products come from agri-food systems - From farm gate to consumers plate - Composed of plant/animal cells Overview: - Food is a made up of portions of carbohydrates, proteins, water, fat, and vitamins and minerals - Their portions and properties influence food product characteristics - Composition directs food preservation and processing techniques Food composition - Most common molecules found: Carbon, Hydrogen, Oxygen, Nitrogen - Other ions like Ca, Fe, Na, Cl exist - Carbs, lipids (fat), minerals, proteins, water, and vitamins describe food composition - Proximate composition - Estimate of nutrition composition - Adds up to 100% - Groups by category not specific molecules - Used to determine storage and shelf life - Ex. - ooked turkey breast has high water content, therefore, it is easily C perishable - Calculating proximate analysis: - There are two types of weight that can used to calculate - Wet basis contains water and can be calculated as is - Dry basis must have its water content subtracted before calculating for more - Dry basis is more common while wet basis is used for nutrition tables Techniques used for each nutrition category - Method principle describe the variable being measured Calculation formula: - Wet basis: weight of component/total weight - Dry basis: weight of component/(total weight-water weight) Using dry matter basis leaves for better comparison Energy value of food - Each macronutrient has different energy per gram - Carb: 4kcal/g - Protein: 4kcal/g - Fat: 9kcal/g - Alcohol: 7kcal/g - To find the energy value multiply the percentage of macronutrient with the total serving size given and then multiply by kcal/g Macromolecules in Food Carbohydrates - Made up of mostly C, H, and O in Cx H2+x Ox - Commonly in linear or chain structure - Molecules with 5 or 6 carbons tend to form rings - Functions - Source of energy - Ex. starch - Source of fibre - Ex. Beta-glucan - Sweeten and enhance flavour of food - Hygroscopic: water retention - Has preservation effects - Source of food for yeast and bacteria - Browning reactions: maillard reaction, caramelization - Browning reactions - Caramelization: decomposition of sugar at high temperature that creates brown polymers - Millard reaction: sugar (and amino acids) react with dry heat to form product with colour, flavour, and aroma of baked goods - Simple structures:monosaccharides/disaccharides - Ie. ribose(5c), fructose(6c), glucose, galactose - glucose+glucose=maltose - glucose+galactose=lactose - glucose+fructose=sucrose - Complex structures:oligosaccharide/polysaccharide - Oligosaccharides - Ie. raffinose, stachyose, and verbascose found in legumes - Insulin is signal for sugar storage and added to foods as prebiotic - Polysaccharides - Ie. starch, cellulose (fibre), pectin (fibre) - Used to increase dietary fibre, thicken foods, form gels (think starch), bind water, and stabilize proteins - Starches: formed by two types of molecules with differentproperties - Amylose: linear chain (function: form gels) - Amylopectin: branched chain (function: viscosity) - Cellulose:found in the plant cell wall an is a formof dietary fibre - Pectin:found in fruits and vegetables and is an intercellularcement - Gum:used to thicken and stabilize food products (ie.agar agar, xanthan - Fun fact: History of high fructose corn syrup - Made by isomerized glucose molecules into fructose - Process developed in the 1959s and released in 1975 - Pros: inexpensive, long shelf time, easy to use Proteins - Made up of amino acids - shape/function determined by the sequence of amino acids - Absorbed by hydrolyzation - Obtained from plant and animal sources - Structures - Primary: sequence of amino acids - Secondary: organization of polypeptide chains (a-helix or b-pleated) - Tertiary: organization of protein chains - Quaternary: structure of overall protein - Proteins are easily denatured by slight change in pH or increase in temperature temperature (does not affect the primary structure - Function: - emulsifier(ie egg yolk) - foaming agent(ie egg whites) - Gelling agent(ie gelatin) - Thickening agent (ie protein) - Binding agent - Amino acids contribute to savory factor of food(flavour) - Proteinprecipitate at isoelectric pointsto createother food products - Isoelectric point: when pH has no net charge on protein - Eg. casein precipitates to form gel that generates curds and whey (from souring milk) Lipids - Oils: liquid at room temp. Made up of saturated fatty acids - Fats: solid at room temp. Made up of UNsaturated fatty acids - Most food lipids are mainly made up of triglycerides - Other lipids: phospholipids, sterols, fat-soluble vitamins, fat soluble pigments - Determine fat properties by esterifying fatty acids to glycerol - Functions - Source of essential fatty acids - Caloric density - Provide satiety - Carry flavours + fat soluble vitamins(A, D, E, K) - Add texture to foods - Heat transfer medium (think: frying) - Emulsifier for immiscible foods (ie milk and butter) - However - Degradation (oxidation & rancidity) of fat can cause off-flavours - Hydrolyticrancidity: free fatty acids released whenfat and water interact - Oxidativerancidity: biochemical reaction betweenoxygen and fats - Long fatty chains are degraded; short chains are released as odorous - Antioxidants are used to prevent oxidation (vitC, vitE) Water and Vitamins Water - Essential for living things - Plants store water in the vacuole - Removing/reducing water in food products is the mainway toprocessand/or preserve - Inhibitmicrobial - Prevent chemical reactions - Other preservation methods (thermal): canning, pasteurization - Meats, fruits, vegetables have the most moisture - Function - Water dissolves flavours, vitamins, and minerals - Provides lubrication formastication(chewing) andswallowing - Aid in nutrientabsorptionfrom intestine into bloodstream - Influence texture in fruits/vegetable and tenderness of meat - Facilitates heat transfer (more than fat) - Facilitate microbial growth - Supports fermentation, spoilage and pathogens - Free water: a portion of water found in food availablefor microbial growth - Easily extracted from food by squeezing, cutting, or pressing - Water activity(aw) describes water availability infood - Aw < 0.5 means little moisture available - Aw > 0.5 means a lot of moisture available - Calculating Aw uses vapour pressure above surfaceof food product over pure water - Aw = p(water above food)/p0(water)answer in percentage - Used to predict reactions - Reduced by adding salts and sugars or through concentration, evaporation, and dehydration process - Bound water - Cannotbe extracted easily - Cannotbe solvent for salts and sugars - Canbe frozen Cannotturn into vapour Minerals next page Micronutrients - Found mostly in fresh and minimally processed food - Can also be added to process food through fortification - Micronutrients may be altered during processing - Thermal reduces vitaC - Flour milling reduces vitaB, minerals, and fibre - Mineralsare represented as ash - Na, Ca, Mn, K aremacrominerals - Fe, Zn, I aretracemolecules - Assist in reactions and formation of body structure - Energy transfer - Vitamins - Reaction regulation in body
