食品分析 食品感观分析 食品分析实验 动植物检验检疫学 食品.ppt

Food Analysis,Advanced course for graduate students majoring Food Process and Safety Feb. 2006,Chapter One General,Necessity of food analysis Quality controlling in the raw material, food processing, and products. Delicious, Nutritional (protein, lipids,carbohydrates, fibre, water,vitamin, etc.) 2) Quality monitoring for food safety Healthy,Careful of your food Sudan Red I is an industrial dye. It can beautify the color of food, and it can lead to cancer.,Inject unknown liquid , perhaps to keep it fresh.,Harmful food package,Hazardous materials exist. Usually it includes industrial CaCO3, cycled plastics, industrial wax, etc. when it contact hot water, or it was heated in the microwave oven, harmful substances was dissolved in the food.,Preservative film,DEHA is a kind of plasticizing agent. When it was heated or contact oil and fats, it can move into the food. It can interrupt endocrine system of people and lead to mammary cancer, infant deformity, and harm reproductive system of males.,Food additives, such as saccharin sodium. They are chemically synthesized. Much more ingestion can induce carcinoma of urinary bladder, harm the liver and nerve system.,Harmful to your health Acrylamide Benzopyrene,Trans fatty acids,Benzopyrene,Cancer,Fats and Oils Cycled from restaurant. Much harmful materials exists in it, such as toxins, trans fatty acids, benzopyrene, etc.,Delicious ?,Food analysis concepts Special research on establishing the method of analyzing the components of food or nutriments and its related principles, thereby evaluating the food quality.,Food analysis contents 1) Nutritional components of food Protein, lipids, carbohydrates, water, vitamin, mineral, fibre, etc. Functional components, such as PUFA(polyunsatuated fatty acids).,2) Analysis of food safety Food additives(e.g. pigment) Residual drug (e.g. pesticide) Food package (e.g. DEHA) Microbial contamination ( e.g. E.coli,toxins) Harmful ingredients (e.g. As) Harmful components produced in food process(e.g. acrylamide),3) Sensory evaluation of food See if new food can be accepted by consumer (delicious or not) , it will be realized by sense organ ( nose, tongue).,Standard 1) Trade standard 2) National standard 3) International standard ISO: International Organization for Standardization WHO: World Health Organization CAC: Codex Alimentarius 4) Advanced international standard regional standard national standard of developed country 5) AOAC Association of Official Agricultural Chemists,How to learn “food analysis”? Knowledge on food processing Principles and practices of instrumentation Theory of methods (physical , chemical, biochemistry, enzymology, molecular biology, etc.),Chapter two Sampling and preparation of samples,Sampling,Sampling concept Drawing representative sample from a bulk of Materials. It should have the characteristics as following: An ideal sample should be identical in all of its intrinsic properties with the bulk of the material from which it is taken.,Importance of sampling Sampling and any subsequent separations may be the greatest sources of error in food analyses. 1)Representative 2) No change or loss 3) No contaminant,Major steps in sampling Identification of the population from which the sample is to be obtained. Selection and obtaining of gross samples of the population. Reduction of each gross sample to be laboratory-sized sample suitable for analysis. One is used for analysis.One should be packed and stored in such a way that no significant changes occur from the moment of sampling until the analysis is completed.,Types of sampling methods 1)Simple random sampling: for populations in which all elements have an equal and independent chance of being included in a sample. 2) Stratified random sampling: by separating the population elements into overlapping groups (strata) and selecting a simple random sample from each strata. 3) Systematic sampling: drawing a 1 in K sample from a list of units. From the sampling frame, a starting point is chosen at random, and thereafter at regular intervals. 4) Judgment sampling: drawing samples based on the judgement and experience of the investigator.,Necessity of sample preparation Complexity of food compositions (components, shape, etc.) Complex action of different components in the food Quantity of components analyzed in the food (toxin,microbe) Unstable components analyzed in the food (some volatile components, compositional changes by action of microbe,enzyme and biochemistry, etc.),Sample preparation,Purpose of sample preparation:Purification of components analyzed, remove the interfering materials. Principles of sample preparation: object in the food should be kept completely.,Methods in the sample preparation 1)Grinding dry and moist materials 2) Enzyme treatment or inactivation 3) Organic matter degradation 4) Distillation 5) Solvent extraction 6)Chromatography 7)Chemical purification 8)Concentration,Grinding dry and moist materials Dry materials: Hammer, ball mills etc 2) Moist material: bowl cutter, meat mincers, colloid mills etc. 3) Extraction can be performed well.,2) Enzyme treatment or inactivation 1) To disintegrate the tissue mildly, avoid the destroy of objective components by acid or alkali. 2) To inactive the enzyme in the tissue, avoid the changes caused by the enzyme catalysis.,3) Organic matter degradation Fundamentals: organic phase into inorganic phase Ashing: samplesashing(500600）-analysis; for example, P analysis. Digesting: samples acid analysis, for example, protein analysis Microwave-digestion: samples-microwave -analysis, for example, Pb analysis. UV photolysis: samples UV(85 )analysis, for example, ion analysis.,4) Distillation Fun