The influence of seasons and ripening time on yeast communities of a traditional Brazilian cheese

The occurrence and effects of the dry and rainy seasons on yeast populations in traditional Serro Minas cheese, one of the most popular cheeses produced from raw milk in Brazil, were studied over the course of 60 days of ripening. Enzymatic activity exhibited by these yeast isolates was also studied. A total of 19 yeast species were identified via sequence analysis of the Dl/D2 domains of the large subunit of the rRNA gene. Fourteen yeast species were obtained from cheese produced during the dry season, and fifteen species were obtained from cheese produced during the rainy season. High diversity indices for the yeast species were determined for cheese manufactured during both seasons (average H-D' = 1.7 and H-R' = 1.5, respectively). The predominant species in Serro Minas cheese included Debaryomyces hansenii, Kodamaea ohmeri and Kluyveromyces marxianus. D. hansenii 28.12 showed low lipolytic and high proteolytic activity. K. marxianus 83F and 60P demonstrated lipolytic and beta-galactosidase activity, respectively. K. ohmeri 88A displayed low lipolytic and beta-galactosidase activity. Maximal lipase, beta-galactosidase and protease activity was observed at 20 degrees C and pH 6.0, 30 degrees C and pH 7.0 and 50 degrees C and pH 6.0, respectively. Considering that D. hansenii 28.12, K. ohmeri 88A and K. marxianus 60P together showed protease, lipase and beta-galactosidase activity in this study, further research on the possibility of including these yeasts as part of a starter culture and research on their effects on the sensory properties of Serro Minas cheese merit more study. (C) 2015 Elsevier Ltd. All rights reserved.