Fortification of yogurt with β-glucans from oyster mushroom

Abstract

Mushrooms are a good source of biologically active substances. Basidiomycete Pleurotus ostreatus is not only widely used in food, but also have immunomodulating, antitumor, antiradical, anti-inflammatory, hypocholesterolic, hypoglycaemic and other beneficial medical effects. It is considered that β-glucans play significant role in the biological activities of the oyster mushroom. The aim of this research was to study the effect of the addition of various β-glucan containing preparations obtained from the submerged biomass of P. ostreatus on the process of milk fermentation in the production of yogurt and properties of the finished product. A total of three preparations were obtained by successive ethanolic and aqueous extractions. Preparations were added to milk in different concentrations before the introduction of starter culture. A starter containing Streptococcus thermophilus and Lactobacillus delbuckii subsp. bulgariсus cultures was used for fermentation. The titratable and active acidity was controlled during the fermentation. Physicochemical, structural-mechanical properties (dynamic viscosity, viscosity loss factor, mechanical stability factor, structure recovery ratio) of the obtained samples were studied. The sensory properties of the products were also evaluated. Results show that the addition of preparations does not adversely affect the fermentation process. Structural-mechanical properties of yogurt samples fortified by β-glucan-containing preparations depend on the preparation and its concentration. Sensory evaluation showed that experimental samples differed not only from the control sample but also from each other. In order to exclude slightly negative effect of some of the introduced components on the sensory characteristics of the product, it is advisable to use thickeners and structure-formers, for example, pectin.