UTRIZATION OF HIGH PRESSURE ON FREEZING AND THAWING OF FOOD

为确定高压冷冻对鸡蛋品质的影响，将蛋冻凝胶、琼脂、高粘弹琼脂、κ-卡拉胶、ι-卡拉胶、κ-卡拉胶+刺槐豆胶、凝胶胶、代用结冷胶和天然结冷胶等凝胶和蛋黄在-20℃的压力下冷冻。在降至大气压后，凝胶在-30℃下储存，然后在20℃下解冻。然后将其与常压(0.1Mpa)下冷冻的凝胶(-20℃、-30℃或-80℃)的滴量、织构和结构进行比较。在不含糖的凝胶中，在0.1、100、600和686兆帕的冷冻条件下，凝胶的质构和结构与原始凝胶有很大不同。另一方面，当所有凝胶在200~400 Mpa冷冻时，冻胶的质量比在0.1 Mpa和100 Mpa(冰I)下冷冻的凝胶更好。然而，质量与未冷冻的凝胶不同。在加压过程中，在0.1、100、500~686 Mpa(冻结)处检测到放热峰。但在200~400 Mpa的压力下，凝胶不会冻结(过冷)，而减压后，凝胶很快就会冻结。因此，200~400 Mpa的变压冷冻能有效地改善冻胶的质量。随着蔗糖的加入，起始冻结温度降低。随着糖含量的增加，凝胶的外观、质地和结构都有所改善。而5种糖(蔗糖、葡萄糖、海藻糖、索比特醇和麦芽糖醇)的结晶大小差异不大。

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).