不同冷藏时间的鳝鱼肉经熟化后质构特性变化及其机理

Effect and Underlying Mechanism of Cold Storage on Textural Properties of Cooked Monopterus albus

通过测定不同冷藏时间的鳝鱼肉经熟化后(100℃、5 min)的蒸煮失水率、质构特性、化学作用力、蛋白质电泳和拉曼光谱等指标变化规律,探讨冷藏对鳝鱼肉熟化后质构特性变化的影响及机理。结果表明,随着冷藏时间的延长,其蒸煮失水率逐渐增加,硬度和弹性无显著性变化(P>0.05),内聚性和胶黏性分别在第2天和第3天显著增加(P<0.05),咀嚼性和回复性呈现先增加后降低的趋势(P<0.05)。价键分析表明,疏水作用和二硫键是熟化鳝鱼肉蛋白间的最主要作用力,贮藏时间越长的鳝鱼肉,经熟化后其疏水作用越低,二硫键含量则呈先增加后降低的趋势。相关性分析表明不同冷藏时间的鳝鱼肉经熟化后二硫键含量与弹性、咀嚼性、回复性之间呈显著正相关(P<0.05)。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析表明分子质量低于30 kDa及分子质量约30、37、60 kDa的蛋白组分可能参与二硫键的形成,进而对熟化鳝鱼肉的相关质构特性产生影响。拉曼光谱结果显示,色氨酸、酪氨酸残基的疏水性降低,这与疏水作用变化趋势一致。二级结构分析结果表明,冷藏前3 d主要是α-螺旋和无规卷曲向β-转角和β-折叠结构转化,后期则由α-螺旋和β-折叠结构转化为β-转角和无规卷曲,蛋白无序化程度增加。综合各项指标表明二硫键和疏水作用成为熟化鳝鱼肉蛋白间的主要作用力,其变化导致蛋白构象趋于无序,进而造成不同冷藏时间的鳝鱼肉经熟化后相关质构特性变化。

The purpose of this study is to assess the effect of cold storage on textural properties of cooked Monopterus albus and to explore the underlying mechanism.Monopterus albus were stored cold for different periods before being cooked at100℃for5min.Cooking loss,textural properties and chemical forces were determined,and sodium dodecyl sulfatepolyacrylamide gel electrophoresis(SDS-PAGE)and Raman spectroscopic measurement were conducted.The results showed that as storage time increased,moisture loss during cooking increased,while hardness and springiness were not significantly changed(P>0.05);cohesiveness and gumminess were significantly increased on the second and third day(P<0.05),respectively;chewiness and resilience increased first and then decreased(P<0.05).Hydrophobic interaction and disulfide bonds were the most important forces between various proteins in cooked Monopterus albus.Hydrophobic interactions tended to decrease gradually whereas the disulfide bonds increased initially and then decreased with increasing cold storage time.For each storage period,disulfide bond content was positively correlated with springiness,chewiness and resilience(P<0.05).SDS-PAGE showed that protein components with molecular mass less than30kDa and equal to approximately30,37and60kDa may be involved in the formation of disulfide bonds,thereby possibly affecting textural properties in cooked Monopterus albus.Raman spectroscopy analysis indicated that the hydrophobicity of tryptophan and tyrosine residues decreased,which was consistent with the change of hydrophobic interactions.The secondary structure analysis indicated the transformation ofα-helix and random coil structures intoβ-turn andβ-sheet occurred mainly during the first three days of cold storage whileα-helix andβ-sheet conformations were transformed intoβ-turn and random coil during the late storage stage,leading to a more disordered structure.Taken together,we concluded that disulfide bonds and hydrophobic interactions are the main forces between various proteins in cooked Monopterus albus,and changes in these forces can cause protein conformation to disordered,thereby leading to changes in textural properties of Monopterus albus after cooking.