4.7 Article

Interfacial and foaming properties of soy protein and their hydrolysates

Journal

FOOD HYDROCOLLOIDS
Volume 23, Issue 8, Pages 2149-2157

Publisher

ELSEVIER SCI LTD
DOI: 10.1016/j.foodhyd.2009.03.015

Keywords

Foam; Soy protein; Hydrolysates; Air-water interface; Surface pressure; Dilatational rheology

Funding

  1. CYTED [105PI0274]
  2. CYCYT [AGL2007-60045]
  3. Junta de Andalucia [PO6-AGR-01535]
  4. Universidad de Buenos Aires
  5. Agencia Nacional de Promocion Cientifica y Tecnologica
  6. Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina

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The objective of the work was to study the impact of soy protein hydrolysis on foaming and interfacial properties and to analyze the relationship between them. As starting material a sample of commercial soy protein isolate was used (SP) and hydrolysates were produced by an enzymatic reaction, giving hydrolysates from 0.4% to 5.35% degree of hydrolysis (DH). In this contribution we have determined foam overrun (170), stability against liquid drainage and foam collapse, and the apparent viscosity of foams produced by a whipping method. The surface properties determined were the adsorption isotherm and surface dilatational properties of two hydrolysates (2 and 5.35% DH, HI and H2 respectively). The hydrolysis of soy proteins increased the surface activity at bulk concentrations where SP adopts a condensed conformation at the monolayer. At concentrations where it adopts a more expanded conformation a very low degree of hydrolysis (H1) also promoted the enhancement of surface activity. However, at 5.35% degree of hydrolysis (H2) the surface activity decreased. Moreover, H2 presented lower surface activity than HI at every bulk concentration. The hydrolysis increased the elastic component of the dilatational modulus and decreased phase angle of films at bulk concentrations below that corresponding to the collapse of So monolayer(2% bulk protein). SP hydrolysis increased foam overrun and the stability against drainage that could be related to increased surface activity of protein hydrolysates. However, the collapse of foams was promoted by hydrolysis and could be ascribed to a decrease of the relative viscoelasticity (higher phase angle) of surface films. The results point out that a low degree of hydrolysis (2-5%) would be enough to improve the surface activity of SP, decrease foam drainage and maintaining a considerable viscoelasticity of the surface films to retard foam collapse. (C) 2009 Elsevier Ltd. All rights reserved.

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