Resistance during Spray drying and thermotolerance of microorganisms isolated from kefir grain

MARINA GOLOWCZYC, JOANA SILVA, ANALIA ABRAHAM, GRACIELA DE ANTONI AND PAULA TEIXEIRA

Lisboa, Portugal

Congreso; European Federation of Food Science and Technology (EFFOST); 2007

Kefir is a fermented milk beverage originating from the Caucasian mountains and commercially produced in Asia, Europe and America. The milk fermentation is achieved by the use of kefir grains, a cluster of microorganisms held together by a polysaccharide matrix. A vast variety of different species of microorganisms forming the kefir grains, comprising yeast and bacteria, have been isolated and identified. Several health promoting properties are associated to kefir consumption. The aim of this work was to study the thermotolerance and survival during spray drying of Lactobacillus plantarum CIDCA 83114, Lactobacillus kefir CIDCA 8348 and Saccharomyces lipolytica CIDCA 812 isolated from kefir grains. All microorganisms were grown in MRS broth at 30 ºC and cells were harvested in the stationary phase of growth. The heat treatment was performed at 55, 60 and 65ºC in skim-milk powder. Spray dried conditions were: outlet air temperature 70, 75, 80 and 85 ºC, inlet air temperature 180 ºC and atomizing air pressure 5 Bar. During the heat treatment and after spray drying, the survivors were enumerated in MRS agar by the drop count technique. The three microorganisms investigated varied considerably in their ability to survive to spray drying process. L. plantarum CIDCA 83114 showed the highest survival rate for all the outlet air temperatures studied. L. kefir CIDCA 8348 and S. lipolytica CIDCA 812 showed a decrease in survival with increased outlet air temperature. L. kefir CIDCA 8348 showed a reduction of 1 log CFU/ml at 80 and 85 ºC. S. lipolytica CIDCA 812 showed a higher loss of viability and no survivors were observed at 85 ºC. The thermotolerance L. kefir CIDCA 8348 was highest in all temperatures investigated. No correlation was observed between the thermotolerance and survival during spray drying.