果汁冷冻浓缩过程中冰晶形成规律的研究

本研究测定了橙汁和菠萝汁的冰点曲线,并以此探讨在果汁冷冻浓缩时水分冻结率的变化规律。结果表明,果汁在开始冻结的温度附近结冰率变化最大;以后逐渐减慢。橙汁和菠萝汁的最大冰晶生成区分别是-0.8～-7.9℃和-0.7～-6.7℃。冷却介质温度越低,冰晶的生长速度越快,但最终冰晶尺寸越小。当介质温度为-10℃左右时,可获得较大的冰晶尺寸。本文也研究了搅拌作用及果汁预处理因素对冰晶生长的影响。

Study on the Regularity of Ice-crystal Forming During the Freeze Concentration of Fruit Juice

The freezing point curves of orange juice and pineapple juice was determined, and the change regularity of water freezing rate during the freeze concentration of the fruit juice was investigated. It is shown that the change rate of freezing ratio is greatest about temperature at which the juice begin to freeze, and then is slow. The ranges of maximum ice-crystal form of orange juiceand pineapple juice are -0.8--7.9℃ and -0.7--6.7℃ respectively. Thelower the temperature of cooling medium is, the quicker the ice-crystals grows but the smaller the final ice-crystal form.Greater ice-crystals will be obtained when temperature of cooling medium is about - 10℃. The effect of other factors, such as stirring and pretreatment of fruit juices, on the ice-crystal growth are also studied.