The effect of Enterococcus faecium subsp. faecium strains on chemical, microbial and sensory properties of doogh during storage

In this study, the effect of different inoculum concentrations of E. faecium subsp. faecium strains on chemical, microbial and sensory properties of doogh was evaluated during two months of storage at 4 and 25°C. As compared with the control samples, samples containingstrain 1 of E. faecium subsp. faeciumand strain 2 of E. faeciumsubsp. faeciumat concentrations of 106 and 108 cfu/ml showed that decreasing of pH and increasing of acidity in the first month of storage.Also, inoculated samples of doogh with E. faecium subsp. faecium strains showed a significant decrease (p˂0.05) in the enumeration of molds and yeasts, coliform and mesophilic microorganisms at both storage temperatures (4 and 25°C). Among the samples, inoculated doogh sample with strains of E. faecium subsp. faecium with concentration of 108 cfu/ml was more effective in reducing the unwanted microbial load. Samples of inoculated doogh with concentration of 108 cfu/ml at 4 °C had an acceptable shelf life up to 50 days, while it was 40 days for the same control sample counterpart. Sensory evaluation showed that inoculated doogh samples were more acceptable than control doogh samples stored at 4°C. Generally, the E. faecium subsp. faecium strains, due to more decreasing of pH and higher acidification, reduced microbial load, and have a positive effect on sensory properties then can be used as a co-culture in the production of fermentation dairy products.