保证食品安全的加工方式（参考）.pptVIP

E.coli is generally the most sensitive. Viruses differ in their sensitivity. Parasites are the most resistant. 大肠杆菌对氯最敏感，各种病毒对氯的敏感性不同，寄生虫对氯的抵抗力最强。 The efficacy of the disinfection process depends on the purity of the water because the disinfectant may be neutralized by organic matter and readily oxidizable compounds in water. Microorganisms that are aggregated or absorbed by a particular material may also be partly protected from disinfection. It is therefore important to treat the water before disinfection to produce a water with a median turbidity not exceeding 1 nephelometric turbidity unit (NTU) and not exceeding 5 NTU in any single sample. 消毒功效取决于水的纯度，因为，消毒剂有可能被水中的有机物质和易氧化的化合物中和。被特殊物质聚集或吸附的微生物较难消毒。因此，消毒前对水进行适当处理，使水的半混浊度不超过1浊度的浊度单位（NTU），在任一纯样品中不超过5NTU是很重要的， This curve shows how growth of microorganisms, production of toxins, and physicochemical reactions are affected by water activity. Dried foodstuffs are most stable at a water activity of about 0.2. 该曲线说明了水分活度对影响微生物的生长、毒素的产生和物理化学反应的影响。水分活度0.2左右的干燥食品最稳定。 Generally, moulds and yeast require lower water activity than most bacteria. Some bacteria, such as S.aureus can grow at quite low aw levels and can cause problems in foods such as salted meats and cheese. 一般而言，霉菌和酵母生长所需的水分活度比多数细菌低。但是，某些细菌，如金黄色葡萄球菌能在相当低的水分活度下生长，并导致咸肉和干酪这类食品产生问题。 The range of water activity levels in foods is quite large. This table shows that water activity is a selective parameter that determines which microbes will grow. 食品中水分活度的范围相当宽。该表说明，水分活度是决定哪些微生物将在其中生长的选择性参数。 At water activity 0.6, food starts to become shelf-stable, as no growth occurs but microorganisms may remain viable. This means that as soon as water is added to dehydrated food, precautions required for a fresh food apply because surviving microorganisms can grow again. 水分活度0.6，食品有稳定的货架期，因为此时微生物不能生长，但是，微生物仍残存于其中。这意味着只要脱水食品的水分含量增加，就必须向对待新鲜食品一样，注意防止（残存）微生物的生长。 Various technologies can be applied to control water activity. Old preservation techniques such as salting and jam makin