The use of Cold Setting Whey Proteins to enhance the Gelation Properties of Foods.

Abstract

The main objective of this project was to produce dried, denatured, whey protein-based powders, which on reconstitution in food formulations show an increased ability to bind water in the presence of added salts, especially in the ambient temperature range. To achieve this, a number of secondary objectives were set to observe the behaviour of the whey protein system. These included the effects of salt on increases in viscosity during the heating process, the requirement for pH adjustment during processing and the ability of the pre-treated whey protein to interact with fat. The main conclusions were as follows: * It was shown that, compared to a commercial 75% whey protein concentrate, a preheated whey protein ingredient (cold-setting whey protein) improved the consistency of surimi and a cold-set dessert system. * For cold-setting applications, the whey proteins need to withstand heating without gel formation. For example, as the protein concentration was increased, the salt concentration had to be decreased and pH increased to prevent the initiation of gelling during processing. When the salt concentration was increased, a lower heat treatment was needed to prevent viscosity increase. However, lower heat treatment resulted in a lower degree of protein unfolding and weaker cold-set gels. This example implies that only certain whey sources are suitable starting materials for cold-set applications. * Model oil-in-water emulsions were studied using whey proteins pre-treated at different homogenisation and heating conditions to evaluate the potential of cold-setting whey proteins in yoghurt, mayonnaise and sauces. It was found that with these pretreatments, emulsion viscosity increases were observed at very low whey protein concentration (< 1%), when salt was added after emulsion formation, indicating that cold-set whey proteins are much more effective gelling agents than normal whey protein ingredients. For this reason, they have potential in acidified dairy products such as yoghurt. * Pre-heated whey protein dispersions are also capable of binding and stabilising calcium phosphate. This property can be exploited in the stabilisation of calcium-fortified milkbased beverages. * The commercial production of cold-setting whey protein ingredients will depend on the ability to retain whey protein solubility during processing. A number of mechanisms exist to achieve this but, in all cases, very exact control of the process is required. * Because low salt levels prevent the aggregation and gelling of denatured whey proteins, whey protein isolate is an ideal starting material for the production of these ingredients, but due to the high cost, de-mineralised whey was chosen instead as the starting material. Careful consideration has also to be given to the processing equipment and the economics involved. * The development of whey protein ingredients especially for cold-set end uses is a product specific exercise. General guidelines were developed in the current work, but further work with industry partners will be necessary before commercial success is achieved.