Desenvolvimento de uma cultura iniciadora para produção de kefir

The kefir is a fermented milk with sweet sour taste, self-carbonated, with low alcohol content, resulting from the metabolic activity of microorganisms present in kefir grains, a complex and specific mixture of bacteria and yeasts surrounded by a polysaccharide matrix. The traditional method of obtaining the kefir cultures by successive reinoculation grain is simple, but with no possibility of control which results in an irregular production. The objective of this study was to isolate and identify microorganisms in kefir grains to be used in the development of a starter culture capable of producing a standardized milk beverage with the typical characteristics of traditional kefir. Three methods for production of kefir were compared: the traditional method used as a control and two methods using the selected starter culture by simultaneous fermentation and subsequent fermentation, respectively. For comparison, the resulting beverages were submitted to physical-chemical, microbiological and sensory determinations. The different methods used in the manufacture of kefir significantly influenced aspects of viscosity and syneresis of products. The traditional technique resulted in a product with lower acidity, while the products developed with starter culture led to shorter fermentation time. The counts of yeasts and lactic bacteria averaged 6.39 and 9.99 log10 colony forming units (CFU). mL-1, respectively. Intentions to purchase products produced by starter culture were similar between them, while the traditional kefir received the highest percentage of negative intention to purchase (73%). The technique of preference mapping showed good correlation with the analyses done by the average tests (Tukey) and frequency analyses, indicating that the samples of starter culture were the most accepted. The method by simultaneous fermentation was considered the most appropriate method for the manufacture of kefir, due to its higher viscosity, lower syneresis and consumer preference for consistency. In conclusion, the starter culture developed in this work can be used to produce kefir as it has led to a product with physical-chemical, microbiological and sensorial characteristics similar or superior to traditional kefir.