Effect of various proteins on characteristics and synerisis of tzatziki

摘要

One of the main problems in tzatziki quality is the phenomenon of synerisis, which is observed when the gel structure collapses and water gets squeezed out. The aim of this project was to minimize synerisis and increase the shelf life of the product during storage at refrigerating temperatures without changing product texture and flavor. This was achieved by the addition of hydrophilic proteins that trap the water within the gel structure minimizing the synerisis effect. Low expressible moisture content prevents grow of microorganisms and, thus, improves the overall quality of the product. Firstly, different samples consisted of yogurt and solutions of albumin, whey proteins, sodium caseinate added in yogurt were prepared. The water content of the samples was that of a real tzatziki system (83% water). The samples of protein-yogurt-water solutions where prepared by adding proteins to yogurt solutions in ratios of 1% and 5% w/w. Measurements of water-holding capacity, moisture content and pH were taken and showed a reduction 5% to 10% of synerisis compared to the plain yogurt solution depending on the type and ratio of added proteins as well as the storage time. The used proteins were analyzed for water holding capacity, solubility and pH. The type and concentration of the added proteins were the factors investigated. Samples were characterized in terms of pH, synerisis, water holding capacity and storage stability. It was found that protein addition (i) improved water holding capacity, (ii) decreased the synerisis effect, and (iii) stabilized the pH of the samples during storage. The optimum conditions (protein type and ratio added protein/yogurt) that yield minimum synerisis without affecting significantly product texture and flavor were determined. Thus, proteins addition seems to be an effective way of producing a stable tzatziki gel system.