第一章食品质量变化精要.ppt

第一章 食品加工保藏技术原理 第一节 食品变质因素 第二节 食品加工保藏技术分类 第三节 栅栏技术 第四节 食品的保质期 一、 食品变质（Food deterioration) Food deterioration is often associated with advanced spoilage, which may make food unfit for human consumption. In the broader sense any adverse change in attributes from an agreed upon measure of quality may be considered deterioration. 凡食品改变了原来的性质和状态而不符合质量要求的现象。 大多数食品从原料收获、屠宰或加工开始，在感官性质、营养价值、安全性和美学性能等方面的吸引力等方面均在逐步变质。 Useful storage life of plant and animal tissues 二、食品变质的主要因素 变质速率的快慢，受到外在因素和内在因素的共同作用。 外在因素包括： 1、微生物（growth and activities of microorganisms, principally bacteria, yeasts, and molds ）； 2、 有害昆虫、寄生虫和啮齿类动物等大生物（insects, parasites, and rodents）； 3、温度（temperature, both heat and cold ）； 4、湿度（moisture and dryness ）； 5、光和其它辐射（light and other radiation ）； 6、氧气（air, and more particularly oxygen）； 7、工业污染物质（ industrial contaminants）； 8、时间（ time）； 9、 掺假 some foods in the presence of others。 内在因素主要包括 1、食品自身的酶作用activities of natural food enzymes和 2、各种物理化学作用（Reaction of Physical-Chemical) 的影响。 These factors are not isolated in nature 这些导致食品变质的因素在自然界中不是孤立的，而是相互联系相互制约的，并随时间的延长而加剧. The range of potentially destructive factors and the great diversity of natural and processed foods is why so many variations of several basic food preservation methods find application in modern food technology. 败坏因素的多样性决定了食品保藏方法的多样性 The essence of food technology may be said to be an understanding of deteriorative factors and their control. 食品工艺的要点就是有关变质因素及其控制。 Effective preservation must eliminate or minimize all of these factors in a given food. （Hurdle technology） （一）微生物 （Bacteria, yeasts and molds） ? Microorganism multiplication on or in foods frequently is the major cause of food deterioration ? not all microorganisms cause food spoilage and many types are used in preserving foods ? microorganisms