食品冷冻冷藏新发展

1、食品冷冻冷藏新发展李云飞2005年10月20日年人均消费水平年人均消费水平年人均消费水平0 0101020203030404050506060kgkg美国美国丹麦丹麦英国英国瑞典瑞典法国法国日本日本中国中国台湾台湾上海上海冷冻产品状况冷冻产品状况冷冻产品状况肉类肉类面食面食水产品水产品果蔬果蔬冷饮冷饮果蔬12% 水产品50% 面食18% 肉类20% 冷饮28%易腐食品低温运输状况0 0101020203030404050506060707080809090100100冷藏运输冷藏运输公路公路铁路铁路发达国家发达国家中国中国冷藏运输公路铁路发达国家80707中国152555(%)易腐食品低温贮藏

2、状况53053026261701706.86.80 0100100200200300300400400500500600600低温库低温库高温库高温库全国全国上海上海万吨易腐食品低温贮藏状况（上海）0 05 51010151520202525303035355050606070708080909020002000年代年代库容量（万吨）库容量（万吨）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特点冻结解冻热导率 W (m K)-12.20.5比热容 kJ (kg K)-12.14.2 食品与介质的温差可充分低不可充分高研究热点问题研究热点问题研究热点问题速冻食品的质量问题 超高压速冻

3、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）水的物理性质第VI族元素氢化物的融点和沸点H2O沸点融点H2SH2SeH2Te分子量温度/ 1000-60-1002040120800The phase diagram of water. l represents the region in which ice XII has been observed by Lobba

4、n 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. Ho

5、rizontal 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.Triple pointsMPaCliquidgasIh0.0006120

6、.01liquidIhIII209.9-21.985IhIIIII213-35IIIIIV344-24liquidIIIV350.1-16.986IIVVI626-70liquidVVI632.40.16VIVIIVIII21005liquidVIVII221681.6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

7、晶形态XII型The H-bond framework of tetragonal ice XIITransition 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

8、 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-FreezingPressure-Shift-FreezingPressure-shift-freezing (A) and pressure assisted thawing (B) of potatos at the phase diagram of waterPressur

9、e-Shift-FreezingPressure-Shift-FreezingFreezing of potato tissue water to ice IIIPressure-Shift-FreezingPressure-Shift-Freezing新鲜目鱼细胞Pressure-Shift-FreezingPressure-Shift-FreezingPressure-Shift-FreezingPressure-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 RTEBexp链段能量与周围的自由体积大小冷冻稳定剂较高的Tg

10、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56.6103. 09 . 02280kg水3101 .155252056.61kJ3104 .1725252 . 49 . 02280kJ08.8204. 09 . 02280kg水3108 .206252008.82kJ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

11、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sxppp水溶液水在压力相同条件下，稀溶液中水的沸点高于纯水的沸点。sxKTT水溶液在压力相同条件下，稀溶液中水的冰点低于纯水的冰点。sxKTT溶液水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（Pa）温度（）压力（Pa）温度（）10130010087352339206110170615402-5123010260-10压力与蒸气体积1克水体积常温常压

12、下1毫升873Pa，5下150000毫升RTMmPV 278K KkmolJ8314 18 0.001kg Pa873TRMmP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。捕水器抽出水蒸气保护油封泵真空泵罗茨泵与油封泵性能10510310110-20255075100压强 Pa抽气速率 影响真空预冷效果的因素v 可用于汽化的水份含量；v 表面组织的性质；v 体表面积大小。果蔬材料果蔬堆放状态v 果蔬堆放密度；v 包装材料的气密性。设备性能v 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 pa

13、ckinghouse真空冷却真空冷却装货移动式真空冷却设备真空冷却冷却曲线Forced-AirHydroIceVacuumTypical cooling time (hr)1-100.1-10.1-0.30.3-220-100Water loss (%)0.1-20-0.5No data2-40.1-2Water contactnoyesyes, unless baggednonoPotential for decay contaminationlowhighlownonelowCapital costlowlowhighmediumlowEnergy costlowmediummediumh

14、ighlowWater-resistant packaging needednoyesyesnonoPortablesometimesrarely donecommoncommonnoFeasibility of in-line coolingrarely doneyesrarely donecommonnoRoomComparison of Produce Effects and Costs for Common Cooling Methods风冷运输风冷运输低温运输国外应用示例Product arrives from the field on line trucks. Some is th

15、en cooled by icing and some is vacucooled.Vacuum cooling involves placing cartons of produce in a chamber where the atmospheric pressure is lowered.国外应用示例This causes the boiling point of water to drop and it is boiled off. Cold water is simultaneously added to the cartons so the product emerges cold

16、 and undamaged.Regular icing involves packing each carton of produce with ice. At 25 pounds per carton, we use tons!国外应用示例Bonipak Produce Company can manufacture 300 tons of ice each day and we can store 400 tons.When large quantities of product come into the cooler over a short period, we cool the produce in our Air Tunnels. We have 8 tunnels, which hold 14 pallets of produce each. The cartons a