Study of the effect of black seed extract on some physicochemical, microbiological and sensory properties of the manufactured yogurt

Abstract

The study aimed to fortify milk prepared for the manufacture of yogurt with different concentrations of aqueous extract of black seed to develop non-traditional therapeutic dairy products with health benefits.Yogurt was produced from whole milk fortified with 0%, 1% and 2% of aqueous extract of black seed, which represent as C, T1 and T2 , treatments respectively. The results indicated that the fortified yogurt treatments maintained a moisture content close to that of the control treatment (C), while after 21 days of storage at a temperature of (5±1) 0 C, a slight decrease in the moisture content was observed for all treatments.No significant differences were observed in the pH value and the total acidity of all the studied treatments immediately after manufacturing.An improvement was observed in the values of the rheological tests that included testing the viscosity and water retention capacity of T1 treatment compared to the control treatment (C).The process of fortification with the aqueous extract also led to a variation in the total numbers of the starter bacteria, as the treatments T1 and T2 excelled in the growth and activity of lactic acid bacteria compared with the control treatment (C), while the results showed that the yogurt treatments fortified by the aqueous extract were free of coliform bacteria, Psychrophiles bacteria, yeasts and molds, starting from one day after manufacture until the expiry of the 21-day storage period.The results of sensory evaluation also indicated the superiority of the yogurt treatments fortified with aqueous extract, especially the T1 treatment with a concentration of 1%, as it obtained the highest scores and excelled in all sensory attributes compared with the control treatment (C).