食品冷冻冷藏新发展.ppt

食品冷冻冷藏新发展,2005年10月20日,年人均消费水平,冷冻产品状况,果蔬12% 水产品50% 面食18% 肉类20% 冷饮28%,易腐食品低温运输状况,(%),易腐食品低温贮藏状况,万吨,易腐食品低温贮藏状况（上海）,冻结速度对食品质量的影响,降温速率与冰晶,冻结与解冻过程特点,研究热点问题,速冻食品的质量问题 超高压速冻技术 快速冷冻技术 部分玻璃化技术 介电解冻技术 实现上述技术的装备 冷链建设与工艺管理问题,螺旋速冻机,螺旋速冻机,螺旋速冻机,单体流化速冻机,单体流化速冻机,低温介质速冻机,低温介质速冻机,低温介质速冻机,隧道式速冻机,氢与电负性很强，且具有独立电子对、原子半径又较小的原子可形成氢键（如氮、氟）,水的物理性质,the phase diagram of water. l represents the region in which ice xii has been observed by lobban et al. (t = 260 k, p = 0.55 gpa) 2. please note that this region is fully surrounded by the stability range of ice v. the inset sketches the pressure induced transition line of ih (red line) as studied by o. mishima 1. the green area indicates the region in which ice xii is successfully formed. horizontal arrows indicate that ih transforms by compression below 150 k to ice xii or high-density amorphous state (hda) and above 150 k to ice iii/ix. the orange area displays the 150 k boundary studied by o. mishima for hda which is equally observed for ice xii.,冰晶形态i型,冰晶形态iii型,冰晶形态iv型,the h-bond framework of rhombohedral ice iv showing the auto-clathrate arrangement with h-bonds passing through the centre of 6 membered rings.,冰晶形态xii型,the h-bond framework of tetragonal ice xii,transition of ice xii towards hexagonal ice upon heating. the upper left photograph a) shows ice xii as recovered from the pressure cell at low temperature. in contrast to high-density amorphous ice it has a milky appearance. the following photographs show the floking of ice xii as it transforms to the lower density forms cubic ice and hexagonal ice (b-d).,冰晶xii型与冰晶i型,冻结与解冻过程,冻结过程,解 冻 过 程,高压冻结试验装置,高压冻结,pressure-shift-freezing,pressure-shift-freezing (a) and pressure assisted thawing (b) of potatos at the phase diagram of water,pressure-shift-freezing,freezing of potato tissue water to ice iii,pressure-shift-freezing,新鲜目鱼细胞,pressure-shift-freezing,pressure-shift-freezing,部分玻璃化技术,部分玻璃化技术,玻璃态dsc曲线,弹塑性与温度关系,玻璃态转变理论,自由体积理论,链段能量与周围的自由体积大小,冷冻稳定剂 较高的tg,冷冻保护剂 较强保水性,常用添加剂对粘度影响,果蔬田间热与呼吸热,the respiration rate and the production of co2 depends mainly on the storage temperature,计算示例,kg水,kj,kj,kg水,kj,水的存在状态,自由水：在组织和细胞中容易结冰、也能溶解溶质的这部分水。,毛细管水细胞间隙内水； 滞化水组织内显微或亚显微 结构与膜 所阻留的水； 流动水植物导管、细胞内液泡中的水。,水的存在状态,束缚水：在组织内通过氢键与其它物质结合的这部分水。其特点是冰点低（约40）；不能作为溶剂。,溶质对冻结与蒸发温度的影响,稀溶液中水的蒸气压比纯水蒸气压低,在压力相同条件下，稀溶液中水的沸点高于纯水的沸点。,在压力相同条件下，稀溶液中水的冰点低于纯水的冰点。,植物细胞结构,叶面组织结构,叶面表层气体运动,叶面表层气体运动,压力与蒸发温度,压力与蒸发温度,压力与蒸气体积,压力与蒸气体积,如果每小时蒸发82kg水，则水蒸气体积达到0.1582100012300m3。 需要真空泵抽出速率为205m3/min。,捕水器,真空泵,罗茨泵与油封泵性能,影响真空预冷效果的因素,可用于汽化的水份含量； 表面组织的性质； 体表面积大小。,果蔬材料,果蔬堆放状态,果蔬堆放密度； 包装材料的气密性。,设备性能,降压速率。,风冷,风冷,负压风冷,水冷,水冷,水冷,冰冷,蒸发冷却,straw