过氧化氢诱导的罗非鱼皮胶原纤维降解过程(Ⅱ)——降解过程中产物组成与性质的变化

研究过氧化氢溶液体系中罗非鱼皮胶原纤维热降解过程,反应体系中降解产物的氨基酸组成、分子质量和性质的变化。结果表明:反应1 h内,释放到溶液的胶原蛋白降解产物极少,不足以测试样品的凝胶强度和黏度。反应1~3 h,反应体系中溶液的表观黏度增加,反应液冷却后可凝结成凝胶,凝胶强度随时间的延长逐渐增大,说明释放到水溶液中胶原分子数量增加,溶质质量浓度提高。反应3~5 h后,反应液表观黏度随时间下降,反应液中溶质质量浓度提高,凝胶的凝胶强度下降,说明这个阶段以原胶原分子肽链的裂解为主体,导致胶原蛋白进一步水解断裂。电泳结果显示,反应4 h的样品,分子质量在130 k D以下的条带比例增加,说明样品中α链断裂片段增加。氨基酸组成分析显示,降解产物与鱼皮氨基酸组成略有差异,但不同反应时间点,明胶产物的氨基酸均没有显著变化,说明过氧化氢协同热效应,主要是通过水解肽键的方式实现胶原纤维向可溶态明胶的转变。

Hydrogen Peroxide-Induced Degradation of Type Ⅰ Collagen Fibers of Tilapia Skin (Ⅱ): Changes in Composition and Properties of Degraded Products

The amino acid composition, molecular weights and properties of degraded collagen fibers of tilapia skin induced
by heat and hydrogen peroxide were studied. Experimental results showed that collagen fibers degradation could be divided
into three stages. At the first stage, collagen fibers contracted when heated and no significant change was observed in the
reaction solution. At the second stage, collagen fibers and microfibers were disrupted and procollagen was released into the
solution, leading to an increase in the apparent viscosity of the reaction solution and the occurrence of gelation when cooled,
with a time-dependent increase in gel strength. At the third stage, the peptide bonds of procollagen were broken, releasing
smaller peptide chains after 3 h and causing a decrease in apparent viscosity and gel strength. The amino acid composition
of the degraded products was slightly different from that of the original collagen fibers and there was no significant change
during different reaction periods. It was proved that collagen fibers can be transformed into gelatin by hydrolysis of peptide
bonds or crosslinking oxidation when heated in combination with hydrogen peroxide treatment.