Heat-Induced Whey Protein Gels: Effects of pH and the Addition of Sodium Caseinate

Abstract

The effects of pH (6.7 or 5.8), protein concentration and the heat treatment conditions (70 or 90°C) on the physical properties of heat-induced milk protein gels were studied using uniaxial compression, scanning electron microscopy, differential scanning calorimetry, and water-holding capacity measurements. The systems were formed from whey protein isolate (10-15% w/v) with (5% w/v) or without the addition of caseinate. The reduction in pH from 6.7 to 5.8 increased the denaturation temperature of the whey proteins, which directly affected the gel structure and mechanical properties. Due to this increase in the denaturation temperature of the β-lactoglobulin and α-lactalbumin, a heat treatment of 70°C/30 min did not provide sufficient protein unfolding to form self-supporting gels. However, the presence of 5% (w/v) sodium caseinate decreased the whey protein thermo stability and was essential for the formation of self-supporting gels at pH 6.7 with heat treatment at 70°C/30 min. The gels formed at pH 6.7 showed a fine-stranded structure, with great rigidity and deformability as compared to those formed at pH 5.8. The latter had a particulate structure and exuded water, which did not occur with the gels formed at pH 6.7. The addition of sodium caseinate led to less porous networks with increased gel deformability and strength but decreased water exudation. The same tendencies were observed with increasing whey protein concentration.

Protein-Based Structures for Food Applications: From Macro to Nanoscale

“…Macro or bulk protein gels are generally evaluated according to their sol-gel transition, thermo-reversibility, and gel strength (Fazani Cavallieri et al, 2010;Picone et al, 2011;Tarone et al, 2013;Chen et al, 2017a;Queirós and Lopes-da-Silva, 2017). The sol-gel transition is used to determine the gelling temperature at specific conditions being useful not only to produce macrogels but also to use this information in the top-down particles production.…”

“…WPI gels can also be induced by extrinsic factors that can modulate their microstructure, water holding capacity, rheological, and textural properties. The use of different salts (e.g., NaCl and CaCl 2 ) (Bryant and McClements, 2000;Kuhn et al, 2010), acidification (e.g., organic acids, glucono-δ-lactone, and HCl) (Picone et al, 2011;Queirós and Lopes-da-Silva, 2017;Wijaya et al, 2017), and enzymes (Spotti et al, 2017) were reported.…”

Propriedades Mecânicas De Géis Simples E Mistos Por Redes Neurais Artificiais

“…Todos os dados experimentais foram baseados em artigos científicos de um mesmo grupo de pesquisa, os quais utilizaram o mesmo equipamento e mesma metodologia para análise das propriedades mecânicas dos géis (Ribeiro et al, 2004;Braga et al, 200;Perrechil et al, 2009;Picone et al, 2011).…”

“…Apesar do grande número de estudos sobre a gelificação de proteínas com ou sem a presença de polissacarídeos e das propriedades mecânicas dos géis (Braga et al, 2006;Perrechil et al, 2009;Picone et al, 2011), existem poucos trabalhos que desenvolveram modelos matemáticos que correlacionem o seu comportamento mecânico-estrutural e os modelos encontrados para esse tipo de sistema complexo são ainda muito limitados (Perrot et al, 2011;Foucquier et al, 2012).…”

The Effect of Processing Parameters and Methylcellulose on Texture and Consumer Acceptability of a Non-Melting Dairy Protein Gel

“…Fine stranded gels are transparent, have thin strands that can be branched to form the network in the gel, and are created by heating proteins that are far from the isoelectric point with low ionic strength (Fennema, 2007). Heat-treated whey protein gels adjusted to a pH of 7 and 3 produced fine stranded gels (Walkenström and Hermansson, 1996;Picone et al, 2011) . Coarse-stranded gels contain small sphere particles that make the gel turbid.…”