pH对大黄鱼肌原纤维蛋白结构性质及乳化性的影响

Effect of pH on the structural properties and emulsification of myofibrillar proteins of large yellow croaker(Larimichthys crocea)

为深入探究大黄鱼肌原纤维蛋白(MP)的乳化性,以满足大黄鱼蛋白质高值化开发利用的需求。实验探究了不同pH对大黄鱼MP结构性质及其乳化性的影响。采用pH分别为2、4、6、8、10、12的低盐磷酸缓冲液处理大黄鱼MP,通过SDS-PAGE分析大黄鱼MP降解情况,利用接触角测量仪和荧光分光光度计考察其疏水性变化。将不同pH下大黄鱼MP溶液与大豆油以体积比为1∶1的比例经高速均质制备乳液,并对其乳滴电位、粒径以及乳液的乳析指数进行测定,综合分析在不同pH下乳液的稳定性。SDS-PAGE电泳结果表明,在pH 4时,大黄鱼MP条带颜色较浅,在pH 6~12时,肌球蛋白重链条带基本消失,肌动蛋白条带颜色逐渐加深,且在浓缩胶顶部出现了高分子聚集物。对接触角和荧光光谱的综合分析表明,大黄鱼MP疏水性随pH增加而增加。对不同pH下MP乳液特性分析显示,在pH 8时,乳滴带负电且Zeta电位绝对值大[(49.63±1.52)mV]、粒径较小、乳液稳定性较好,而pH 12条件下容易出现破乳,不利于乳液的稳定。在pH 8时,大黄鱼MP结构更有利于提升乳液稳定性。研究表明,在弱碱性条件下更有利于大黄鱼MP形成稳定的乳液体系。pH对大黄鱼MP结构性质和乳化性的影响探究,有望为大黄鱼MP在食品工业中的开发利用提供理论依据。

Properties of myofibrillar proteins(MPs)in Larimichthys crocea remain to be further studied to meet the high-value development and utilization of MPs.The purpose of this study is to investigate the effect of differ-ent pH on the structural and emulsifying properties of myofibrillar protein in L.crocea.MP from L.crocea was treated with low-salt phosphate buffer at pH 2,4,6,8,10 and 12,and MP degradation was analyzed by SDS-PAGE.Moreover,the hydrophilicity of MP was investigated by contact angle and fluorescence spectrophotometry.Emulsions were prepared with MP solution at different pH and soybean oil at ratio of 1∶1(V/V)by high-speed homogenization.The stability of emulsions was determined by analyzing the droplet potential,particle size and the emulsion index of emulsions.At pH 4,the band color of MP in SDS-PAGE was light.At pH 6-12,the myosin heavy chain band largely disappeared;however,the actin band gradually deepened in color and macromolecular aggregates appeared at the top of band.The comprehensive analysis of contact angle and fluorescence spectrum showed that the hydrophobicity of MP increased with pH.Meanwhile,the MP emulsions were negatively charged with the Zeta potential absolute value of(49.63±1.52)mV and small emulsion droplets at pH 8,exhibiting better stability than MP emulsions at other pH values.However,the MP emulsions showed poor emulsion stability and even demulsification occurred at pH 12.The change of MP structure was beneficial to improve the stability of MP emulsions at pH 8.These results can provide a theoretical basis for the development and application of MP from L.crocea in the food industry.