Obtaining Kefir Microcapsules in Powder Form by Spray Drying

Kefir is presented as gelatinous grains which, when inoculated in milk, produces a fermented milk acidified with probiotic activities. The reduction of water activity is a strategy to increase the shelf-life of food products and has been used to increase stability and viability of microorganisms. Obtaining Kefir powder can be a strategy to increase shelf life, reduce storage costs, and increase practicality in the marketing and the use of the product. Spray drying is a thermal process, which must be controlled because the viability of the microorganisms can be affected by numerous factors. This study aimed to obtain a fermented powder product from kefir grains that preserve characteristics and survival of microorganisms after dehydration by Spray Drying. The kefir was fermented in 12 and 25% (w/w) reconstituted skim milk powder and then dried. Grain growth, yield, moisture, nutritional composition, kefiran content and microbiological survival of the obtained powders were evaluated. The product was characterized by differential exploratory calorimetry (DSC) and Scanning Electronic Microscopy (SEM). After drying, the yield and kefiran content of the samples with initial 12% solids were higher than 25% and the moisture was lower. A high survival rate for acidic lactic acid bacteria in the powdered product (107 CFU/g) produced at 12% (w/w) was found. However, yeast did not survive the process. Microcapsules observed by SEM exhibited a rounded shape with a preserved surface, while DSC indicated a probable disruption above 50°C. The powder produced at 12% showed better fermentation characteristics, process yield, moisture of the final product and survival of microorganisms. The product contains equivalent to 50mg of kefiran/20g, indicating that in this fermentation and drying conditions, exopolisacarides have been preserved. The microcapsules produced by the Spray Dryer technique have a rounded shape with a preserved surface, without pores, however rough and varied in size. The technique used was efficient by generating intact microcapsules containing potentially probiotic live microorganisms.