Antimicrobial and Antioxidant Activity of Green Tea-Derived Metabolites in Yogurt and Cheese Formulations

Abstract

The use of bioactive compounds derived from plants species in dairy products is a promising solution to develop functional foods with a new antioxidant and antimicrobial activity. The metabolites in green tea (Camellia sinensis) are catechins and other metabolites derived from the phenolics, some of which may interact with the dairy components and processing conditions and alter the stability and function of the metabolites. The present study aimed to develop the enriched green tea metabolite yogurt and green tea metabolite cheese and compare them with regard to their antioxidant, antimicrobial, physicochemical, microbiological and sensory properties during the refrigerated storage for 30 days. A green phenolic tea extract was prepared and its phenolic and flavonoid content and major catechines (EGCG, EGC, ECG and EC) were characterized. The yoghurt and cheese were fortified with different levels of the extract and the control products (no green tea) were added to the products. In the case of refrigerated storage, the formulated products were tested for their pH, titratable acidity, moisture content, texture, colour, phenolic retention, antioxidant activity, antimicrobial activity, microbial viability and sensory acceptability. Green tea addition resulted in the increase of phenolic contents and flavonoids contents and an increase in the antioxidant activity (DPPH assay, ABTS assay and FRAP assay) was significant. Fortified products showed the concentration dependent antimicrobial activity against selected foodborne and pathogenic bacteria as well. As the concentration of the green tea was increased, however, the color, flavor and astringency of the tea also increased in size, suggesting that there is a balance between the bioactive functionality and sensory acceptability of the green tea. The stability of the green tea metabolites was found to be different in the two dairy products; but the dairy matrix of the product significantly affected the stability and functionality of the metabolites of the green tea. The moderate supplementation was suitable in terms of the antioxidant and antimicrobial properties, physicochemical stability, microbial compatibility and sensory properties.