氧化亚油酸对肌原纤维蛋白胶凝行为及热诱导凝胶体外消化率的影响

Effect of oxidized linoleic acid on gelling behavior of myofibrillar protein and in vitro digestibility of heat-induced gel

在脂质氧化体系(0.5~10.0 mmol/L亚油酸,3750 U/mL脂肪氧合酶)条件下,探究了氧化诱导的肌原纤维蛋白(myofibrillar protein,MP)理化性质、凝胶性能以及凝胶体外消化率的变化。结果表明,随着氧化亚油酸(oxidized linoleic acid,OLA)浓度的增加,肌原纤维蛋白的总巯基、自由氨基含量、内源性色氨酸荧光强度、Zeta电位绝对值和蛋白溶解度显著降低(P<0.05),而蛋白质的交联和聚集作用增强。随着蛋白氧化程度的加剧,MP凝胶的微观结构变得更加粗糙,蒸煮损失显著增加(P<0.05),凝胶强度也有所下降,同时MP凝胶的消化率也显著降低(P<0.05)。拉曼光谱中色氨酸残基(I760/I1003)和酪氨酸双重态(I850/I830)的拉曼强度比结果表明,氧化削弱了凝胶内部的疏水相互作用以及MP分子间的氢键作用力,进一步解释了MP凝胶性能的下降。因此,尽管在许多情况下活性氧(reactive oxygen species,ROS)的存在可以促进MP的凝胶化,但是由OLA诱导的氧化似乎并不利于MP的凝胶化。

Oxidation-induced changes in physicochemical and gel properties of myofibrillar protein(MP)and in vitro digestibility of the heat-induced gel were investigated using a lipid-oxidation system(0.5-10.0 mmol/L linoleic acid and 3750 U/mL of lipoxidase).Results showed that with the oxidized linoleic acid(OLA)concentration increased,total sulfhydryls,free amines,tryptophan fluorescence,absolute value of Zeta potential and the solubility of MP were decreased significantly(P<0.05),while protein crosslinking and aggregation were enhanced.Moreover,with the intensification of protein oxidation,the microstructure of MP gels became rougher and the cooking loss increased markedly(P<0.05)and the gel also became weaker and the digestibility of MP gel decreased significantly(P<0.05).The intensity ratios of tryptophan residues(I760/I1003)and tyrosine doublet(I850/I830)in Raman spectra indicated that oxidation weakened the hydrophobic interaction within the MP gels and the hydrogen bonds between MP molecules,respectively,which further explained the reduction of MP gel properties.Hence,although in many cases reactive oxygen species(ROS)could promote MP gelation,the OLA-initiated oxidation appears to be detrimental to MP gelation.