英文版食品添加剂概述 (2).pdf
Food microbiological Contamination and Prevention Food Safety Contents 01 02 03 Sources and pathways of food contamination Food microbiological contamination and prevention Food spoilage and its impact on health Definition of food contamination Food Contamination refers to the entry of toxic and hazardous substances into the food during the cultivation,breeding,production,processing,storage,transportation,sale,cooking,and until the table,causing changes of nutrition and sensory and may cause harm to human health.3 Classification and Hazards Classification:Biological contamination Chemical contamination Physical contamination Hazards:Food sensory traits and nutritional value Adverse effects on health 4 Sources of food microbial contamination Raw material contamination;Contamination during production,processing,transportation,storage,and retails;Contamination by employees;Contamination during cooking.1.Source and route 5(1)Food ingredients Moisture:free water;bound water;water activity(Aw).Nutritional components:a good medium for microorganisms.Antibacterial ingredient:antiseptic and fresh-keeping effect.(2)Physical and chemical properties of food pH:Most bacteria grow best at a pH around 7.0.Osmotic pressure:Low permeability;High permeability.Biological structure:Foods with intact appearance can be stored for a long time.2.Growth conditions of microorganisms in food 6(3)Environmental factors Temperature:psychrophilic;mesophilic;thermophilic.Oxygen:aerobic type;anaerobic type;facultative anaerobic type.Humidity:It has a greater impact on food moisture and microbial growth on the surface of food.7 Food microbiological contamination and prevention(1)Common food bacteria Bacterial microflora:The type of bacteria and their relative quantities that coexist in food.(2)The significance of the bacterial microflora Determine the degree and characteristics of food spoilage under the action of bacteria;It can be predicted according to the physical and chemical properties of food and the environmental conditions;It can estimate the extent and characteristics of food spoilage;1.Bacterial contamination of food 8(3)Bacterial pollution indicators to evaluate food hygiene quality and the food hygiene significance(1)Colonies number and its significance Colonies number:refers to the total number of bacterial colonies formed by cultivating in the unit mass(g)and volume(ml)of the sample under strict specified conditions(medium,pH,temperature,time,counting method,etc.),expressed as a colony-forming unit(CFU).Food hygiene significance:As a sign that the food is contaminated with bacteria;It can be used to predict the shelf life of food.9(2)Coliform and its significance Coliform:aerobic and facultative anaerobic Gram-negative Bacillus which can ferment lactose and produce acid and gas under certain culture conditions.Coliform:maximum probable number(MPN)Food hygiene significance:As an indicator of food contamination by human and warm-blooded animal feces;As an indicative bacteria for food contaminated by intestinal pathogenic bacteria.10 Contamination by mold and mycotoxins and its prevention 1.Fungi and Mycotoxins(1)Definition:Fungi:A class of eukaryotic cell-type microorganisms that do not contain chlorophyll,have no root,stem,or leaf differentiation,and have cell walls.Mycotoxins:toxic metabolites produced by fungi.(2)Characteristics of fungal production:Fungal toxin production is limited to a few toxin-producing fungi;The toxigenic ability of the same toxigenic strain has variability and mutability;The production of mycotoxins by toxin-producing strains does not have strict specificity;Toxins produced by toxin-producing fungi require certain conditions.11(3)Conditions for fungus toxin production:Substrate;Moisture;Humidity;Temperature;Ventilation.(4)Main toxin-producing fungi and Main mycotoxins.(5）Food hygiene significance of fungal contamination:Contaminated food causes losses;People and animals eating food and feed contaminated with it can cause mycotoxin poisoning.12 2.Aflatoxin 1.Chemical structure and properties Structural formulas of several aflatoxins 13 2.Metabolic pathways and metabolites;3.Toxicity conditions and contamination of food;Toxicity conditions:25 33,Aw 0.93 0.98,delayed toxicity.Most frequent food source is grain oil and its products:corn,peanut,cottonseed oil.4.Toxicity Acute toxicity:liver injury;acute poisoning;Chronic toxicity:disturbance of growth;subacute or chronic liver injury;Carcinogenicity:The strongest chemical carcinogen,mainly causing liver cancer;5.Preventive measures:Anti-mildew;Remove toxin;Setting AF limit standards in food.14 3.Fusarium toxin 1.Trichothecenes:cytotoxicity;immunosuppression;teratogenicity.2.Zearalenone:reproductive system toxicity;immunotoxicity.3.Butyrolactone:rotten hoof disease.4.Fumonisin:neurotoxicity;chronic kidney toxicity;carcinogenicity.5.Preventive measures:Anti-mildew and detoxification;Strengthen the inspection;Setting the standards for the limit in food.15 4.Ochratoxin Ochratoxin A:Very acute toxicity,target organs are kidney and liver;Embryo toxicity and teratogenicity;Kidney carcinogen National food safety standards:less than 5.0 g/kg in cereals,beans and their products,roasted coffee and curry.5.Patulin Toxicity:acute poisoning;teratogenic effect Preventive measures:Anti-mildew;Setting limit standard:50 g/kg.16 6.Other mycotoxins Aspergillus versicolor Acute toxicity:liver and kidney necrosis Carcinogenicity Penicillium Hepatotoxicity(cyclochlorotin and 1uteoskyrin produced by penicillium insula)Neurotoxicity(yellow-green penicillin)Renal toxicity(citrus penicillin)17 Food spoilage 1、Causes and conditions Food spoilage:Refers to the process in which the original chemical properties or physical properties of foods change under the action of various factors mainly caused by microorganisms,reducing their nutritional value.Causes and conditions:microorganism Food composition and properties:enzymes;nutrients and moisture;physical and chemical properties;food status.Environmental factors:temperature,humidity,oxygen,sunlight(ultraviolet)exposure,etc.18 2.The chemical process of food spoilage 1)Protein breakdown:proteases and endopeptidases;2)Fat rancidity:hydrolysis and oxidation;3)Carbohydrate decomposition:food acidity increases;3.Identification indicators of food spoilage 1)Sensory identification:sight;smell;touch;taste 2)Physical indicators 19 3).Chemical identification Total Volatile Basic Nitrogen(TVBN):Chemical Index of Fish and Meat Protein Spoilage Identification;Trimethylamine:Determining the freshness of aquatic products;Histamine:reaching 200 mg/100g can cause allergic food poisoning in humans;K Value:Identification of early fish spoilage,K40%,with signs of spoilage;pH:Spoilage starts to decrease slightly and then rises;Peroxide value and acid value:early indicators of fatty acid failure;4).Microbiological examination:colony-forming unit(CFU);Coliform 20 4.Hygienic significance and handling principles of food spoilage 1).Hygienic significance：Food spoilage changes the sensory traits;The nutritional value is seriously reduced;There may be pathogenic bacteria and toxigenic fungi,causing adverse reactions in human body.2).Handling principles：Timely and accurate identification;Strict control;With the principle of ensuring human health;Consider the specific situation.21 01 Sources and pathways of food microbial contamination 02 Health effects of food bacterial and mold contamination 03 Identification of food spoilage Summary 22 Measures to prevent spoilage of food?Discussion questions 23 I.Food cryopreservation Refrigerated;Frozen storage II.Heat sterilization and preservation Pasteurization;Pressure sterilization;Ultra-high temperature instant sterilization III.Hypertonic preservation Salting method;Sugar pickling method;Increase acidity IV.Dehydration preservation V.Preservative preservation VI.Irradiation preservation Thank you for 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