Gels additional whey proteins

Figure 3. Response surface contour plots (15) for cysteine (x,) and CaCh (Xi) addition to 10% whey protein dispersions at pH 7.0 on hardness (y,), cohesiveness (yi), springiness (ys), and compressible water (yj of gels prepared by heating at 100°C for 15 min...

Whey protein concentrates (WPC), which are relatively new forms of milk protein products available for emulsification uses, have also been studied (4,28,29). WPC products prepared by gel filtration, ultrafiltration, metaphosphate precipitation and carboxymethyl cellulose precipitation all exhibited inferior emulsification properties compared to caseinate, both in model systems and in a simulated whipped topping formulation (2. However, additional work is proceeding on this topic and it is expected that WPC will be found to be capable of providing reasonable functionality in the emulsification area, especially if proper processing conditions are followed to minimize protein denaturation during their production. Such adverse effects on the functionality of WPC are undoubtedly due to their Irreversible interaction during heating processes which impair their ability to dissociate and unfold at the emulsion interface in order to function as an emulsifier (22). 

Several proteins have been studied and reported to form nanotubes to date. However, the only food protein currently known to possess this ability is alpha-lactalbumin (Graveland-Bikker and de Kruif 2006). Alpha-lactalbumin is one of the key components in whey protein with an isoelectric point (pi) of 4—5. In addition, it s the main protein in breast milk (Lonnerdal and Lien 2003). Observed earlier as the micro-structured stiff gel by Ipsen et al. (Ipsen et al. 2001), self-assembly of alpha-lactalbumin into nanotubes is achieved by its incubation with a protease from Bacillus licheniformis (BLP) acting on the Glu-X and Asp-X bonds, in the presence of Ca ... 

It was further found that an upstream heat treatment also helps to improve the Tg effect in milk with the casein present in micellar form, in addition to integrating the whey proteins in the gel. The increased Tg effect in milk, which was heat treated at higher levels above pasteurisation level. The same applies for milk which was UHP treated, as shown by Lauber (2002). This can be explained by the heat inactivation of a so-called Tg-inhibitor substance present in milk (De Jong et al. 2003). BOnisch et al. (2006) also proved that the inhibitor substance is located in the milk serum and demonstrated the effect of heat treatment for systems, where only the miUc serum... 

Cold-set whey protein gels obtained by addition of calcium ions to preheated whey proteins have been used to deliver iron (Remondetto et al. 2002). By modulating the conditions of formation, gels with different microstructures (particulate or filamentous) were formed with different encapsulating properties. Filamentous whey protein gels were more efficient than particulate gels in delivering bioavailable iron to the intestine, as less iron was released at acidic but more at alkaline pH (Remondetto et al. 2004). 

Schorsch et al. (2001) examined the effects of denaturation of whey proteins in the presence and absence of casein micelles on gel properties. Heat treatment sequence was found to influence the acid gelation properties of casein-whey mixtures. Denaturation of whey proteins in the absence of casein micelles induced more rapid gelation on addition of acid. Gels made from these milks had a more particulate gel structure than gels made from casein-whey mixtures which were heated without prior denaturation of the whey proteins. 

Solutions of whey protein isolate (4%, 7.5%, and 11% w/w in demineralized water) were heated at 68.5°C for 3 hr. After cooling to ambient temperature, parts of the protein solutions of 7.5% and 11% were diluted to final concentrations of 4% by addition of demineralized water. Ethylbutyrate or diacetyl was added to all solutions to final concentrations of 150 ppm GDL was added to the solutions with final protein concentrations of 4%, 7.5%, and 11% (w/w), to a final concentration of 0.32%, 0.52%, and 0.86% (w/w), respectively. After addition of GDL the pH decreased slowly to a final value of 5.0, toward the pi of the protein (pH 5.1). Table 1 lists the protein concentrations of the five gels used during heating and gelation. 

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