摘要
提出采用真空方式对液体进行冻结,并对抽空的温度、压力及释放热量的现象进行热力学分析。实验运用自行研制的真空冷却试验台,以水、糖水溶液及盐水溶液为冻结材料,实时检测降温与冻结过程中样品内外各点温度与压力的变化曲线,观察样品的变化状态。通过实验,了解了水与二元溶液真空冻结压力与温度的关系和冻结的特性,包括溶液的降温特点、沸腾现象、凝固现象等。实验结果显示,纯水的冰质地较致密而光滑;盐水的冰质地较松软,空隙较大,有明显的冰颗粒;糖水的冰,质地更加的松软,颗粒细腻,类似于冰沙。最后对采用真空技术应用于食品的冷却与冻结工业进行了展望。
This article proposes the vacuum way to freeze liquid, and carries on thermodynamic analysis on the phenomena of temperature, pressure and heat-releasing in the process of decompression. The experiment makes use of the vacuum cooling test-bed, and its freezing materials are water, syrup and brine. The changes of temperature and pressure inside and outside the sample are measured real-time in the course of cooling and freezing, and the changed conditions of the sample are observed also. Through the experiment, we find out the relation with pressure and temperature of sample in vacuum freezing and the characteristics of sample in- cluding cooling, boiling and solidifying phenomena. We find that pure water ice has a dense and slippery texture, brine ice has a soft texture and a large space inside with clear ice granules, and syrup ice like sands is softer with fine granules. This article forecasts the vacuum technique applying to the cooling and freezing of food industry.
出处
《食品科技》
CAS
北大核心
2007年第7期80-83,共4页
Food Science and Technology
基金
上海市重点学科建设项目(T0503)。
关键词
真空冷却
真空冻结
水
二元溶液
vacuum cooling
vacuum freezing
water
duality solution
