Lecture 2 - Proximate Analysis

Lecture 2 - Proximate Analysis - FOOD FEEDS COMPOSITION...

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Unformatted text preview: FOOD / FEEDS COMPOSITION Proximate Analysis Why look at food composition? • Food analysis – the development, application and study of analytical methods for characterizing foods and their constituents. • Why is this important? • about Information about produce foods are safe andinformed nutritious, Information foods, produce foods foods, that are safe and nutritious, allowthat the consumer to make decisions. allow the consumer to make informed decisions. – Government Regulations? Maintain quality of foods, ensure food industry makes safe food foods with high quality, fair competition between companies, • Maintain quality of foods, ensure industry makes safe foods eliminatewith economic fraud. high quality, fair competition between companies, eliminate economic fraud – Quality Control? • Ensure food composition doesn’t change, characterize raw materials Ensure food composition doesn't change, characterize raw materials. Nutrient Density? • All foods are not created equal…. • The amount of nutrients in comparison to caloric content Broccoli: 27 kcal Cupcake: 131 kcal – Nutrient-dense foods – Empty calorie foods Source: Nutrition for Foodservice and Culinary Professionals, 7th ed - Proximate analysis - Determine the composition of a food product FEED SAMPLE Air dry 1. MOISTURE DRY MATTER on i t c a r t x e r e Eth 2. ETHER EXTRACT Extr act with ethe r Kjeldahl 4. NITROGEN Residue Filtrate Boil in alkali Residue Ignite Boil in acid ASH + Crude Fibre Filtrate Ignite 3. ASH Ash 5. CRUDE FIBRE Moisture = Water weight before and after its baked to nothing FEED SAMPLE Air dry 1. MOISTURE DRY MATTER Why is determining water content in particular important? - Water is weightis and is part ofand the price of feedof the price of feed •Water weight is part - Water is weight and must shipped •Water isplays weight must shipped - Moisture content a roleand in storage conditions - Moisture in foods dilutes energyplays and nutrients •Moisture content a role in storage conditions - Proper moisture important for optimum intake and performance •Moisture in foods dilutes energy and nutrients •Proper moisture important for optimum intake and performance % moisture = weight loss wet weight of sample x 100% % dry matter = 100 - % moisture Potential sources of error? •Drying method removes butcompounds also other compounds - Drying method removes water, but also water, other volatile (SCFAvolatile & some minerals) - Slight underestimation of dry weight some minerals) •Slight underestimation of dry weight Differences in human and agricultural applications? (SCFA & Ether Extract = Crude Fat FEED SAMPLE Air dry DRY MATTER n o i t c a r t ex r e Eth 2. ETHER EXTRACT 1. MOISTURE % crude fat = weight of crude fat wet weight of sample Potential Errors? What•elseWhat comes out else in the ether extract? comes out in the - Chlorophyl, resins, waxes (not nutrients) ether extract? Changes in current food labelling - Newer, more sensitive, methods – Chlorophyll, resins, waxes (not nutrients) • Changes in current food labeling – Newer, more sensitive, methods x 100% FEED SAMPLE Air dry 1. MOISTURE DRY MATTER on i t c a r t x e r e Eth 2. ETHER EXTRACT Why is it important to measure ASH content? Residue Ignite 3. ASH - Nutritional labelling •Nutritional labelling - Quality and taste of food - Microbiological stability •Quality of food - Nutritional requirements •Microbiological stability - Processing •Nutritional requirements •Processing Ash = Mineral Content % Ash = weight of ash wet weight of sample x 100% Potential Errors? - Volatile mineral? Iron, lead, copper, zic, etc • Volatile minerals? Iron, lead, copper, zinc, etc. - Individual minerals? no about individual minerals • infoIndividual minerals? sodium content now mandatory on human food labels – No info about individual minerals – Sodium content now mandatory on human food labels FEED SAMPLE Air dry 1. MOISTURE DRY MATTER on i t c a r t x e r e Eth 2. ETHER EXTRACT Kjeldahl protein 4. NITROGEN Residue Ignite mineral 3. ASH What assumptions are made for the Kjeldahl analysis? - All nitrogen is in protein - All•All protein contains 16% nitrogen nitrogen is in protein •All protein contains 16% nitrogen Nitrogen = Crude Protein 3 Main Steps to the Kjeldahl Analysis 1. Digestion – A homogenous sample mixed with sulfuric acid (nitrogen into ammonia) 2. Distillation – separating the ammonia 3. Titration – quantifying the amount of ammonia with a standard solution % crude protein = N in sample x 6.25 x 100 wet weight of sample Where do we get 6.25? • Kjeldahl Analysis Assumption: ***ALL protein has 16% nitrogen • 100% (protein) ÷ 16% (nitrogen) = 6.25 • Therefore: Nitrogen * 6.25 = Crude Protein Kjeldahl Analysis Potential Errors? • Assumes all proteins have 16% nitrogen • Actual range is 13-19% – Peanuts have….5.46 – Milk has….6.38 • Other forms of N: – Nitrates, nitrites, urea, nucleic acids, etc interpreted as protein Sample Question What is the conversion factor to be used if a food product has 20% nitrogen? 100% protein / 20% = 5.0 So the new equation to calculate crude protein would be… % crude protein = N in sample x 5.0 x wet weight of sample 100 FEED SAMPLE Air dry 1. MOISTURE DRY MATTER on i t c a r t x e r e Eth 2. ETHER EXTRACT Extr act with ethe r Kjeldahl 4. NITROGEN Residue Filtrate Boil in alkali Residue Ignite Boil in acid ASH + Crude Fibre Filtrate Ignite 3. ASH Ash 5. CRUDE FIBRE Crude Fibre = Fibre % CRUDE FIBRE = (wt of ASH + Crude Fibre) – wt of ASH wet weight of sample x 100% Crude Fibre • Potential Errors? • Underestimates fibre – why? – hemicellulose, pectin, hydrocolloids are slightly soluble • Fibre components? • Crude fibre ≠ Dietary fibre – Crude fibre lignin and cellulose – Dietary fibre cellulose, hemicellulose, pectin, hydrocolloids and lignin. Nitrogen Free Extract (NFE) = Digestible Carbohydrate (CHO) • Mainly starches & sugars % NFE = 100 – (% moisture + % crude fat + % ash + % crude protein + % crude fibre) • Potential Errors? NFE accumulate al the errors thatof exist forERRORs the other components NFE accumulates ALL the that exist for the other components General Comments on Proximate Analysis • No information on ‘digestibility’ • No information on specific amino acids, minerals, lipids, or carbohydrates • Still used in food labelling and animal feed analysis • Has provided the basis for developing more advanced analyses 250g Pasture Grass or Salad Green 80% Moisture 50g Dry Matter (DM) 8g 1% Crude Fat 3.2% Crude Protein 5% of DM 16% of DM 5.4% Crude Fibre 8g 27% of DM 12% of DM 2.4% Ash wet weight calc. NFE = CHO = 100% – (80% + 3.2% + 2.4% + 5.4% + 1%) = 8.0% OR Starting from DM, 20% – (3.2% + 2.4% + 5.4% + 1%) = 8.0% dry weight Dietary Fibre as a human can not breakdown • Non-digestible complex CHO • Structural part of plants digestible and fermentable are not the same thing fermentable - think bacteria in the stomach Insoluble Soluble Lignin Pectins Gums Mucilages Cellulose Hemicellulose Remains intact through intestinal tract (does not dissolve in water) Forms gel (does dissolve in water) Food/Feeds Composition: (1) Van Soest Method (2) Southgate Method Van Soest Method for Fibre Analysis in Feeds (Detergent Fibre Analysis) •Quantifies fermentable and non-fermentable CHO for agricultural applications •Differentiates between insoluble fibre components: • Cellulose & Hemicellulose • Lignin •Poorly differentiates sugars, starches, cell solubles Southgate Method •Provides information about sugars, starch and fibre •Useful for human nutrition, food labeling…but not agricultural applications •Does not differentiate fibre components Crude Fat (Ether Extract) Digestible CHO (NFE) Southgate analysis Crude Protein (Kjeldahl) Nutrition News Multiple choice question from previous lecture (1) : Q: Which of the following is an example of an anabolic pathway? A) Proteins are broken down into amino acids B) Palmitic acid is oxidized, ending in the production of acetyl CoA C) Glucose is incorporated into glycogen D) The conversion of pyruvic acid to ethanol ANSWER: C...
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