现代食品化学研究进展 1 水.ppt

molecular mobility is an important factor affecting the chemical stability of food. 在食品保藏温度低于玻璃化温度时，所有的扩散限制的变化都会受到很好的限制。 分子流动性与食品性质的相关性 2、玻璃化温度（Tg）对食品的扩散限制性（diffusion-limited）的稳定性有着密切的关系 Tm～Tg范围内，T下降，Mm减少。在此范围内食品的稳定性也依赖温度，并与（T－Tg）成反比。 分子流动性与食品性质的相关性 3、在溶解或融化温度Tm范围内Mm和扩散限制性食品的性质与温度的关系 水含量越高，玻璃化温度越低。纯水的Tg最低，为-135℃。若Tg高于环境温度时，则该食品体现在常温下也是稳定的。水含量强烈影响Tg. 分子流动性与食品性质的相关性 4.水含量强烈影响Tg Tg’是最大冷冻浓缩液的玻璃化温度，是Tg的一个特定值。 注意：Tg强烈依赖水分含量和溶质的种类 ，但Tg’只依赖溶质的种类。 分子流动性与食品性质的相关性 5.溶质的种类强烈影响Tg和Tg’ 二者相互补充，非相互竞争 Aw法主要注重食品中水的有效性，如水作为溶剂的能力。 Mm法主要注重食品的微观黏度（Microviscosity）和化学组分的扩散能力。 In conclusion， the molecular mobility approach is a novel complement to the aw method of understanding the role of water in food spoilage. In general, Mm is better for diffusion limited reactions, frozen foods and physical changes, they are about equal for understanding crispness and stickiness and aw is preferred for dried foods and non-diffusion limited processes. Points of interest 三种研究食品稳定性的互补方法 估计扩散限制的性质，Mm方法更为有效，Aw无用。 估计保藏到室温时导致的物性改变时，Mm和Aw大致相同。 估计不含冰的产品的微生物生长和非扩散限制的化学反应速度时， Aw 方法更为有效，Mm不可靠。 1、以猪肉、乳粉为例，观察水分相转移； 2、资料分析（近年发表的最新国外资料） Chapter 1 water 22 March - World Day for Water 2006 Water and Culture. Coping with Water Scarcity—2007 Water always finds a way out. Water is gold Water is the source of all life. Water products and its processing. purified water, mineral water… Health water who am i? my name is water without me, crops die animals die, people die industries die that’s me water but what surprise me is do you people know? who am i? i doubt, you let your industrial waste pollute me when i come in abundance to water your crops you complain but do you know who am i? my name is water i have come to save lives not to destroy that is me water To keep water in ones mouthTo keep a secret. It is like drinking a glass of waterIt is very easy to do. To make a hole into the water Making vain attempts. Youre in hot waterYoure in trouble. A fish out of waterNo