食品分析 食品感觀分析 食品分析實(shí)驗(yàn) 動植物檢驗(yàn)檢疫學(xué) 食品

1、Food Analysis,Advanced course for graduate students majoring Food Process and SafetyFeb. 2006,Chapter One General,Necessity of food analysis Quality controlling in the raw material, food processing, and produ

2、cts. Delicious, Nutritional (protein, lipids,carbohydrates, fibre, water,vitamin, etc.) 2) Quality monitoring for food safety Healthy,,Careful of your foodSudan Red I is an industrial dye.

3、 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, indu

4、strial 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

5、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.,Malachite green is a kind of dyes. It can kill fungi,

6、and can length the life of fish in the transportation. The chemical is highly toxic, residual, and it can lead to carcinosis. Malachite green is banned in the aquiculture.,Food additives, such as saccharin sodium. They a

7、re chemically synthesized. Much more ingestion can induce carcinoma of urinary bladder, harm the liver and nerve system.,Harmful to your health AcrylamideBenzopyrene,Trans fatty acids,Benzopyrene,Cancer,Fats and Oils

8、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

9、 components of food or nutriments and its related principles, thereby evaluating the food quality.,Food analysis contents1) Nutritional components of food Protein, lipids, carbohydrates, water, vitamin, mineral

10、, 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)

11、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

12、by consumer (delicious or not) , it will be realized by sense organ ( nose, tongue).,Standard 1) Trade standard2) National standard3) International standard ISO: International Organization for Standardization

13、 WHO: World Health Organization CAC: Codex Alimentarius4) Advanced international standard regional standard national standard of developed country 5) AOAC Association of Official Agricul

14、tural Chemists,How to learn “food analysis”?Knowledge on food processingPrinciples and practices of instrumentationTheory of methods (physical , chemical, biochemistry, enzymology, molecular biology, etc.),Chapter tw

15、o 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

16、 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)Re

17、presentative 2) No change or loss 3) No contaminant,Major steps in samplingIdentification of the population from which the sample is to be obtained.Selection and obtaining of gross samples of the population.

18、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 u

19、ntil 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 samplin

20、g: 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 fra

21、me, 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 preparationComplexity o

22、f food compositions (components, shape, etc.)Complex action of different components in the foodQuantity of components analyzed in the food (toxin,microbe)Unstable components analyzed in the food (some volatile compone

23、nts, 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 samp

24、le preparation: object in the food should be kept completely.,Methods in the sample preparation1)Grinding dry and moist materials 2) Enzyme treatment or inactivation3) Organic matter degradation4) Distillation5) So

25、lvent extraction6)Chromatography7)Chemical purification8)Concentration,Grinding dry and moist materialsDry materials: Hammer, ball mills etc2) Moist material: bowl cutter, meat mincers, colloid mills

26、 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

27、, avoid the changes caused by the enzyme catalysis.,3) Organic matter degradationFundamentals: organic phase into inorganic phaseAshing: samples—ashing(500~600℃）--analysis; for example, P analysis.Digesting: samples–

28、 acid – analysis, for example, protein analysisMicrowave-digestion: samples-microwave -analysis, for example, Pb analysis.UV photolysis: samples– UV(85 ℃)—analysis, for example, ion analysis.,4) DistillationFundamenta

29、ls: distill the volatile components by water, or other solvents.,5) Solvent extractionFundamentals: solubility in different solvents.Such as water, ethanol, or CO2.,6)ChromatographyAbsorption chromatography Absorb s

30、ome components to purify the object.Partition chromatography Different ability of distribution in two mediator.one phase is mobile, the other is immobile. Such as HPLC.Ion chromatography Ion exchange between ions.