The effects of partial hydrolysis on the functional properties of almond protein isolate(API)were investigated by treating the isolate with alcalase enzyme(2.4U/g)and a subsequent polymerization of API was studied using the enzyme,transglutaminase(121U/g).The result obtained showed that partial hydrolysis could induce structural changes in almond protein,mainly reflecting at the molecular weight,duration of hydrolysis,and the active site of the enzymes.On comparing the two enzymes’ability to react on API,enzyme alcalase resulted in producing hydrolysates with the highest protein solubility of 89.38%,surface hydrophobicity of 62.68,and foaming expansion of 31%at the 60th minute of hydrolysis and produced lower molecular weight peptides.Although alcalase API hydrolysates improved the protein’s functionality,the enzyme failed to increase the substrate’s emulsion and foaming stabilities.On the other hand,transglutaminase enzyme produced higher molecular weight peptides and excelled in enhancing the stability of emulsion and foam along with the elevation of%degree of hydrolysis.
In this study,heat-denatured and alcalase-hydrolyzed whey and soy protein films/coatings containing marjoram essential oil(MEO)and thyme extract(TE)were investigated comparatively in terms of physicochemical and functional properties.Heat-denaturated high protein solutions produced self-standing,smooth,transparent and viscoelastic films in the presence of glycerol.Enzymatic hydrolysis provided transparency,elasticity and extensibility to the films of low protein solutions.The addition of MEO and TE triggered hardness and brittleness especially in hydrolyzed high protein films and remarkably changed film color,thickness and viscosity possibly affecting surface adherence of films.Heat denatured films exhibited higher water vapor permeability(WVP)than alcalase-hydrolyzed ones.The lowest hardness was obtained in hydrolyzed low protein films with considerable adhesiveness.Hydrolyzed protein solutions coated to cheese provided better protection against moisture loss and MEO added films caused elevated hardening of cheese.MEO and TE incorporated in film matrices were seemed to suppress mycelial growth and sporulation of Aspergillus niger.This study presented valuable new findings on functional protein films produced by enzymatic hydrolysis as an alternative to heat treatment.
以蓝圆鲹(Decapterus maruadsi)分离蛋白为原料,采用碱性蛋白酶对其进行限制性酶解,研究水解度(degree of hydrolysis,DH)对分离蛋白酶解产物溶解性、持油力、乳化性与起泡性等功能特性的影响。结果表明,碱性蛋白酶酶解产物的相对分子质量显著下降。酶解可有效提高分离蛋白的溶解性,其溶解度随DH增加而增加。与对照组相比,分离蛋白经酶解后,产物乳化性与起泡性均显著提高,并呈现先升高后降低的趋势。不同DH酶解产物在pH值为4.0时的乳化性和起泡性最低;当pH值为10.0时,DH5(DH=5%)的乳化性最高((100.9±0.7)m2/g);当pH值为7.0时,DH5起泡性最高((227.3±3.8)%)。除DH20外,其他组的持油力均有显著提高,其中DH5的持油力最高,达3.50 g/g(油/蛋白)。结果表明,一定程度的水解可以显著提高蓝圆鲹分离蛋白的功能特性。本研究为鱼蛋白在食品蛋白配料中的应用提供了一定理论参考。
