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1、保证食品安全的食品加工,食品质量与安全专业 王春玲,1、Introduction (3),That is why there is a need for 这就是 为什么对以下两点有需要的原因 Food preservation food industry 食品的保藏 食品工业生产 Food transportation food retail 食品的运输 食品的零售,Historically, objectives of food technologies have been : 自古以来，食品加工技术的目的在于： preservation of food 食品获得良好的保藏性 renderi
2、ng food more palatable and digestible 食品更加美味可口和容易消化吸收,2、Introduction (4),In modern times, food technologies are applied with the additional objectives : 在当代，食品加工技术还运用于以下几方面： developing new food products 开发新食品 giving food desired functional properties 赋予食品更多的功效 improving nutritional and organoleptic
3、quality 提高食品的营养价值和口感 ensuring safety 保证食品的安全性,3、Introduction (5),4、Introduction (6),Microorganisms in food are 食品中的微生物 helpful: for fermentation 有益之处：发酵 competitive: cause spoilage 竞争性：导致食品腐败 hazardous: cause foodborne disease 危害性：导致食源性疾病,To understand : 需要了解： how different food technologies can be
4、used to prevent spoilage and/or control hazards in foods 防止食品腐败和（或）控制潜在危害的食品加工技术不同 the factors (parameters) which influence the process and thus the safety of the final products 影响加工过程以及终产品安全的各种因素（参数） how to monitor these factors 如何监控这些因素,Objective学习目标,第二节 保证食品安全的食品加工技术,Food technologies can be clas
5、sified into those that : 食品加工技术可归纳成以下三类： render food safe 提高食品的安全性； control contaminants i.e. prevent growth of microorganisms or production of toxin(s) 控制污染，即防止微生物生长或产生毒素 prevent (re-) contamination 预防（二次）污染,Classes of food technologies食品加工技术的类型,一、提高食品安全性的技术（一）、加热处理（二）、冷冻（三）、辐照（四）、化学消毒（五）、高压技术,二、控制
6、污染的技术,（一）温度（冷持、热持） （二）pH（酸化、发酵） （三）水分活度（盐腌、糖渍、干燥、冷冻） （四）防腐剂（杀菌素、亚硝酸盐）,三、防止再次（二次）污染的技术,（一）包装技术 （二）设备消毒 （三）食品加工设备的卫生设计,一、影响食品安全的食品因素,1、温度 2、水分活度 3、pH 4、氧气,C (Minimum) 最低温度,B (Optimum)最适温度,A (Maximum) 最高温度,How temperature affects growth rate of a bacterial population 1、温度对细菌群落生长速率的影响,Temperature range
7、for growth of pathogens 致病菌生长的温度范围,Temperature C Min. Opt. Max.,Penicillium verrucosum 疣孢青霉 0 20 31 Aspergillus ochraceus 赫曲霉 8 28 37 Aspergillus flavus 黄曲霉 10 32 42 Fusarium moniliforme 串珠镰孢霉 3 25 37,Temperature range for grow of toxigenic moulds 产毒素霉菌生长的温度范围,Temperature zones 温度范围,Psychro trophic
8、pathogens嗜冷致病菌,L . monocytogenes 单核细胞增生李斯特菌 Y . enterocolitica 小肠结肠炎耶尔森氏菌 C . botulinum type 肉毒梭状芽孢杆菌,Water is required for the growth and metabolism of microorganisms 水是微生物生长和新陈代谢必需的物质 All the water in foods is not available for microorganisms 并非食品中的水分都能被微生物利用 The degree of availability of water is
9、 measured by water activity (a w ) 用水分活度a w 衡量有效水分的含量 Chemical and enzymatic reactions are also affected by availability of water 化学反应和酶反应也受有效水分的影响,Water activity 水分活度,a w is the ratio of water vapour pressure of food (p) to that of pure water (po) at the same temperature. a w指相同温度下，食品的水蒸汽压P和纯水的蒸汽压P
10、0之比。 a w = p/ po 0 a w 1,Water activity (definition)水分活度a w的定义,Water activity (3) 水分活度a w,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,Aw,Reaction rate 反应速率,Lipid oxydation 油脂氧化,Non-enzymatic Browning 非酶褐变,Enzymatic activity 酶的活力,Growth of: Moulds 霉菌 Yeasts 酵母 Bacteria 细菌,Minimum levels of aW permitting grow
11、th ( at near optimum temperatures )微生物生长必需的最低水分活度（在接近最适温度下）,MouldsAspergillus chevalieri 曲霉0.71霉菌Aspergillus ochraceus 曲霉0.78Aspergillus flavus 黄曲霉0.80Penicillium verrucosum 青霉0.79Fusarium moniliforme 串珠镰孢霉0.87 YeastsSaccharomyces rouxii 鲁氏酵母0.62酵母Saccharomyces cerevisiae 啤酒酵母0.90 BacteriaBacillus c
12、ereus 蜡状芽孢杆菌0.92细菌Clostridium botulinum (proteolytic) 0.93 肉毒梭状芽孢杆菌（蛋白水解型）Clostridium botulinum (non-proteolytic) 0.97 肉毒梭状芽孢杆菌（非蛋白水解型） Escherichia coli 埃希氏大肠杆菌0.93Salmonella 沙门氏菌0.95Staphylococcus aureus 葡萄球状杆菌0.83,Range of aW in foods and their microbial flora食品中aW的范围及其微生物菌群, 0.98,Fresh meats 鲜肉 F
13、resh fish 鲜鱼 Fresh fruits 鲜果 Fresh vegetables新鲜的蔬菜 Canned vegetables in brine 罐装盐水蔬菜 Canned fruit in light syrup (3.5 % salt, 26% sugar) 低盐罐装水果（盐3.5%，糖26）,(C. perfringens, 产气荚膜梭菌 Salmonella) 沙门氏菌,(Pseudomonas) 假单孢菌,0.93 - 0.98,Fermented sausages 发酵香肠 Processed cheese 加工干酪 Bread 面包 Evaporated milk 炼乳
14、 Tomato paste 番茄酱 (10% salt, 50% sugar) （10盐。50糖）,(B. cereus, 蜡状杆菌 C. botulinum, 肉毒梭菌 Salmonella 沙门氏菌) lactobacilli, bacilli and Micrococci 乳酸菌，芽孢杆菌，微球菌,Range of aW in foodsand and their microbial flora,0.6 - 0.85,Xerophilic fungi喜旱真菌,Halophiles 嗜盐生物 Osmophilic yeasts 耐高渗透酵母,Dried fruit 干果 Flour 面粉
15、Cereals 谷类 Salted fish 咸鱼 Nuts 坚果,0.85-0.93,aw can be reduced by : 下述三种方法能减小aw： Removing water (drying) 除去水分（烘干） Decreasing availability of water by crystalization (freezing) 通过结晶（冷冻）减少有效水分 Decreasing availability by binding water with water binding agents e.g. salt, sugar 利用盐、糖这些亲水试剂与水分子的结合减少有效水分,Water activity 水分活度,aw 1.00 0.99 0.98 0.96 0.94 0.92 0.90 0.88 0.86,Concentration of NaCl and glucose at various aw values (at 25C) 25C时不同浓度食盐和葡萄糖溶液的aw,% w / w Glucose 葡萄糖 0.00 8.90 15.74 28.51 37.83 43.72 48.54 53.05 58.45,% w /
