Whey proteins, adsorption

The carrier materials used for enzyme adsorption must have a highly porous character and a pore size distribution, which should facihtate a free diffusion of enzyme into the carrier. Furthermore, substrate and product should also be able to diffuse freely. This is especially important in the case of large protein substrates, where diffusion into the pore can be a problem (e.g. whey protein and casein). 

Courthaudon, J.-L., Dickinson, E., Matsumura, Y., Williams, A. (1991b). Influence of emulsifier on the competitive adsorption of whey proteins in emulsions. Food Structure, 10, 109-115. 

Khalloufi, S., Corredig, M., Goff, H.D., Alexander, M. (2009). Flaxseed gums and their adsorption on whey protein-stabilized oil-in-water emulsions. Food Hydrocolloids, 23, 616-618. 

Proteins that remain in whey after removing casein from milk are recovered as whey protein concentrates by precipitation with added polyphosphate or other polyvalent anionic compounds, ultrafiltration, ion exchange adsorption, gel filtration, or a combined acid and heat precipitation process. Whey protein concentrates are also manufactured by a combined process involving electrodialysis, concentration, lactose crystallization, and drying (Richert 1975 Morr 1979 Marshall 1982 Anon. 1982 Muller 1982B). 

Shimizu, M., Kamiya, T., and Yamauchi, K. 1981. The adsorption of whey proteins on the surface of emulsified fat. Agric. Biol. Chem. 45, 2491-2496. 

Interactions between proteins and polysaccharides give rise to various textures in food. Protein-stabilized emulsions can be made more stable by the addition of a polysaccharide. A complex of whey protein isolate and carboxymethylcellulose was found to possess superior emulsifying properties compared to those of the protein alone (Girard et al., 2002). The structure of emulsion interfaces formed by complexes of proteins and carbohydrates can be manipulated by the conditions of the preparation. The sequence of the addition of the biopolymers can alter the interfacial composition of emulsions. The ability to alter interfacial structure of emulsions is a lever which can be used to tailor the delivery of food components and nutrients (Dickinson, 2008). Polysaccharides can be used to control protein adsorption at an air-water interface (Ganzevles et al., 2006). The interface of simultaneously adsorbed films (from mixtures of proteins and polysaccharides) and sequentially adsorbed films (where the protein layer is adsorbed prior to addition of the polysaccharide) are different. The presence of the polysaccharide at the start of the adsorption process hinders the formation of a dense primary interfacial layer (Ganzelves et al., 2008). These observations demonstrate how the order of addition of components can influence interfacial structure. This has implications for foaming and emulsifying applications. 

Patino, J.M.R., Nino, M.R.R., and Sanchez, C.C. Adsorption of whey protein isolate at the oil-water interface as a function of processing conditions a rheokinetic study, /. Agric. Food Chem., 47, 3640, 1999. 

The preferential adsorption of caseinates over whey proteins was demonstrated by Britten and Giroux (1991b) and Hunt and Dalgleish (1994). a-la and P-lg showed similar affinity for adsorption at an interface (Dalgleish et al 1991). Dalgleish et al. (1991) also compared surface concentration of ovalbumin with that of P-lg and reported that p-lg had a much greater affinity for the interface. The egg yolk protein phosvitin also exhibited lower affinity for the interface compared with P-casein and p-lg (Dickinson et al., 1991). 

Hunt, J. A. and Dalgleish, D.G. 1994. Adsorption behaviour of whey protein isolate and caseinate in soya oil-in-water emulsions. Food Hydrocolloids 8 175-187. 

Figure 4.41 Production of whey protein isolate (WPI) by ion exchange adsorption (from...

It has been shown that, in mixtures of proteins in emulsions, formed at neutral pH and moderate tern peratures, there is generally no selectivity for the interface. For example, there is no preferential adsorption between the proteins when a mixture of P-lactalbumin and 6-lactoglobulin is homogenized with oil the amounts of protein which are adsorbed are strictly in proportion to their concentrations (104). The same is true when a mixture of sodium caseinate and whey protein is used as the surfactant in an emulsion (55). The only case where preferential adsorption has been tmly observed is when B-casein is used to displace adsorbed... 

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