How to tailor heat-induced whey protein/κ-casein complexes as a means to investigate the acid gelation of milk—a review

Abstract

The heat treatment of milk greatly improves the acid gelation of milk and is therefore largely applied in yoghurt manufacture. During the heat treatment, soluble and micelle-bound whey protein/κ-casein complexes are produced in milk. The complexes and their physico-chemical properties have been held responsible for the early gelation point, the increased final firmness and for the serum retention capacity of the acid gels made of heated milk. They are suspected to bring new functionalities to the casein micelles and to help the formation of interactions when building the gel network. In order to investigate the type of interactions that the complexes can affect throughout the acid gelation of milk, an original strategy would be to control the physico-chemical properties of the whey protein/κ-casein soluble complexes and to use them as vectors to modify the possible interactions in the milk. In that perspective, the different physico-chemical properties of the whey protein/κ-casein soluble complexes that are thought to significantly affect the acid gelation behaviour of the casein micelles are listed. Then, the physical, chemical and biological means that could possibly be applied to the formation of complexes in order to modulate each of the targeted property are reviewed and evaluated. In order to open a large choice for future investigation, these methods were found in a larger literature resource than milk, including other protein systems like model whey protein solutions or non-dairy globular protein systems. The food-compatible

Changing the isoelectric point of the heat-induced whey protein complexes affects the acid gelation of skim milk

“…In line with this hypothesis, Morand, Guyomarc'h, and Famelart (2011a) further proposed that the role of the heat-induced whey protein/k-casein complexes in affecting the interactions in acidified skim milk could be investigated using model soluble complexes with modified interaction properties as a means to modify the colloidal interactions between the casein micelles.…”

Increasing the hydrophobicity of the heat-induced whey protein complexes improves the acid gelation of skim milk

“…Changes in the size and thiol/disulfide distribution of the heatinduced whey protein complexes are likely to affect acid gelation (Donato & Guyomarc'h, 2009;Morand et al, 2011a). Therefore, these properties were measured for all the control and modified samples to anticipate possible bias.…”

“…Heat-denatured whey protein complexes can be used in place of the whey protein/k-casein complexes (Morand, Guyomarc'h, Pezennec, & Famelart, 2011b;O'Kennedy & Kelly, 2000;Schorsch, Wilkins, Jones, & Norton, 2001) and may be used as vectors to modify the acid gelation behaviour of skim milk (Morand, Guyomarc'h, & Famelart, 2011a).…”

Current ways to modify the structure of whey proteins for specific functionalities—a review

“…When heating model solution of whey protein isolates at 15 or 20 g.kg, Morand et al (2011b) found that the hydrodynamic diameter of the resulting aggregates decreased from over 400 nm to ∼100 nm when κ-CN was added prior to heating. The presence of as less as 5% w/w of the total protein as κ-CN is sufficient to divide the size of the aggregates by about twofold (Morand et al 2011a). On the other hand, whey proteins reciprocally protect κ-CN (glycosylated and unglycosylated forms) from extensive fibrillation (Fig.…”

“…2); β-LG has a higher effect than α-LA. Hence, either the whey proteins or the κ-CN assemble into large structures (μm scale) when heated in isolated form, but assemble into small aggregates (0.1-μm scale) when heated together Morand et al 2011a). Equally, the shape of the co-aggregated whey protein and κ-CN is intermediate between branched, fractal aggregates of whey proteins and elongated fibrils of κ-CN (Leonil et al 2008).…”