Emulsification performance and interfacial properties of enzymically hydrolyzed peanut protein isolate pretreated by extrusion cooking

In this study, peanut protein isolate (PPI) was modified with extrusion pretreatment and papain-induced proteolysis. SDS-polyacrylamide gel electrophoresis showed that extrusion pretreatment conducted at 130 degrees C substantially increased the protease accessibilities of the major constitutive proteins (conarachin and arachin) in EPPI (extrudates of PPI), resulting in a remarkable increase in the degree of hydrolysis (DH) and protein solubility for the hydrolysates. Analysis of droplet size distributions and microstructures of oil-in-water model emulsions formed by PPIH (PPI hydrolysates) and EPPIH (EPPI hydrolysates) with different DH showed that extrusion pretreatment led to a marked enhancement in the emulsification performance for the hydrolysates. EPPIH (6.2% DH) was capable of producing a stable emulsion (20 vol% sunflower seed oil) with fine droplets (d(32) = 0.4 mu m, d(43) = 1.6 mu m) at 2.5% (w/v) sample content, whilst the equivalent emulsions made with control PPI and PPIH (0.9% DH) required 6.5% and 5.5% (w/v) level of sample, respectively. Based on investigations of surface pressure versus sample concentration profiles and saturation surface Loads (Gamma(sat)) for some selected PPIH and EPPIH, it was found that with most insoluble protein particles in EPPIH being enzymically hydrolyzed and becoming soluble, the production of surface active peptides with low Gamma(sat) was substantially promoted during enzymic proteolysis, which was responsible for the efficient use of EPPIH (6.2% DH) on generating and stabilizing small emulsion droplets against bridging flocculation during homogenization. These results indicated that hydrolyzed PPI could be used an efficient food emulsifying agent with extrusion pretreatment substantially increasing its protease accessibility. (C) 2017 Elsevier Ltd. All rights reserved.

在本研究中，采用挤压预处理和木瓜蛋白酶诱导的蛋白水解对花生分离蛋白（PPI）进行改性。十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳显示，在130℃下进行的挤压预处理显著提高了EPPI（花生分离蛋白挤压物）中主要组成蛋白（伴花生球蛋白和花生球蛋白）对蛋白酶的可及性，导致水解度（DH）和水解产物的蛋白质溶解度显著增加。对具有不同水解度的PPIH（花生分离蛋白水解产物）和EPPIH（花生分离蛋白挤压物水解产物）所形成的水包油模型乳液的液滴尺寸分布和微观结构分析表明，挤压预处理使水解产物的乳化性能显著提高。在样品含量为2.5%（w/v）时，EPPIH（水解度为6.2%）能够产生稳定的乳液（含20%体积分数的葵花籽油），且液滴细小（d(32)=0.4μm，d(43)=1.6μm），而用对照花生分离蛋白和PPIH（水解度为0.9%）制备的等效乳液分别需要6.5%和5.5%（w/v）的样品量。通过对一些选定的PPIH和EPPIH的表面压力与样品浓度曲线以及饱和表面负载量（Γ(sat)）的研究发现，由于EPPIH中大多数不溶性蛋白质颗粒被酶水解而变得可溶，在酶解过程中，具有低Γ(sat)的表面活性肽的产生显著增加，这是EPPIH（水解度为6.2%）在均质过程中能够有效生成和稳定小乳液液滴、防止桥连絮凝的原因。这些结果表明，水解后的花生分离蛋白可作为一种高效的食品乳化剂，挤压预处理可显著提高其对蛋白酶的可及性。（C）2017爱思唯尔有限公司。保留所有权利。