| چکیده انگلیسی مقاله |
Background and objectives: Kefir is one of the oldest traditional beverages produced by lactic-alcoholic fermentation of milk. On the other hand, milk whey, a by-product of the cheese-making industry, has high contents of valuables nutrients. However, it is usually discarded in Iran, which causes contamination of the environment around the milk processing plants, specially surface and underground waters. Whey fermentation by isolated kefir starter cultures could be a sensible solution towards solving this problem. In the present study, various ratios of starter culture of kefir grain were used for production of a fermented beverage using whey as the substrate. Materials and methods: Acidic whey was used to produce a fermented beverage. Culture media were prepared using various ratios of lactic acid bacteria, yeasts, and acetic acid bacteria isolated from kefir strains and used in the production of the beverage. Keeping constant the incubation time (24 h ) and temperature (25ºC), substrate (pasteurized whey), inoculation rate (3% – 5%), and mixing rate (90 rpm), samples of the beverage with various ratios of the cultures were produced and analyzed for sugar, fat, protein, riboflavin, alcohol, carbon dioxide, dry material and ash. Three different essences, namely, those of Mentha paprika, Anethum graveolens, and Thymus vulgaris were added to the beverage samples, which were then tested for organoleptic properties. Results: Beverage samples were produced using an inoculation rate of 3% individual starter cultures and mixed cultures of Lactobacilli, Coccci, and yeasts. After finding the best ratio in each case, inoculation rates of 3% and 5% were used. Based on organoleptic and chemical (acidity and carbon dioxide) properties, out of the 61samples produced 8 were judged to be desirable. Conclusion: Based on the results it can be concluded that, with regard to color, flavor and aroma, the beverage with Mentha paprika essence is the most desirable. Also, results showed that beverage samples produced with 3% (v/v) lactic acid and acetic acid bacteria and 2% yeast culture (v/v) were the best with respect to quality and acceptability. |