UTRIZATION OF HIGH PRESSURE ON FREEZING AND THAWING OF FOOD

为了确定高压冷冻对品质的影响，将凝胶（蛋奶冻凝胶、琼脂、高粘弹性琼脂、κ-卡拉胶、ι-卡拉胶、κ-卡拉胶+槐豆胶、凝乳胶、替代结冷胶和天然结冷胶）和蛋黄在0.1 ~ 686 MPa、约-20℃下冷冻。还原至常压后，-30℃保存，20℃解冻。然后与在大气压（0.1 MPa）下（-20℃、-30℃和-80℃）冷冻的凝胶进行滴液量、织构和结构（冷冻扫描电镜观察）的比较。在0.1、100、600和686 MPa冷冻条件下，无糖凝胶的质地和结构与原始凝胶有显著差异。另一方面，当所有凝胶在200 ~ 400 MPa下冷冻时，冷冻凝胶的质量比在0.1和100 MPa（冰I）下冷冻的凝胶更好。然而，其质量与未冷冻的凝胶不同。加压过程中，在0.1、100、500 ~ 686 MPa（冷冻）处检测到放热峰。但在200 ~ 400 MPa时，凝胶不冻结（过冷），而减压后，凝胶迅速冻结。由此可见，在200 ~ 400 MPa的压力变换冷冻条件下，所有冷冻凝胶的质量都得到了改善。随着蔗糖添加量的增加，初始冻结温度降低。随着糖的添加，所有凝胶的外观、质地和结构都有所改善。5种糖（蔗糖、葡萄糖、海藻糖、山梨醇和麦芽糖醇）的结晶尺寸差异不大。

To determine the effect of high-pressure-freezing on quality, gels (egg custard gel, agar, agar with high visco-elasticity, κ-carrageenan, ι-carrageenan, κ-carrageenan+locust bean gum, curdlan, substituted gellan gum and native gellan gum) and egg yolk were frozen at 0.1〜686 MPa at ca. -20℃. After reducing to atmospheric pressure, gels were stored at -30℃ then thawed at 20℃. The amount of drip, texture and structure (cryo-SEM observation) were then compared with gels frozen (-20℃, -30℃ or -80℃) at atmospheric pressure (0.1 MPa). In gels without sugar, frozen at 0.1, 100, 600 and 686 MPa, texture and structure differed significantly from original gels. On the other hand, when all gels were frozen at 200〜400 MPa, the quality of frozen gels improved compared to gels frozen at 0.1 and 100 MPa (ice I). However, quality differed from unfrozen gels. During pressurization exothermic peaks were detected at 0.1, 100, 500〜686 MPa (freezing). However, at 200〜400 MPa, gels did not freeze (supercooling), while after depressurization, the gels froze quickly. Thus, pressure-shift-freezing at 200〜400 MPa was effective in improving the quality of all frozen gels. With the addition of sucrose, the initial freezing temperature decreased. With the increase of sugar, appearance, texture and structure of all gels improved. However, there was no great difference in crystal size among the 5 kinds of sugar (sucrose, glucose, trehalose, solbitol and maltitol).