Role of selected yeasts in cheese ripening: an evaluation in aseptic cheese curd slurries

Yeasts are found within the surface microflora of many cheese types, but not much is known about their direct contribution to cheese ripening. The aim of this study was to investigate, on a laboratory scale, the direct influence of yeasts on cheese ripening by means of aseptic cheese curd slurries. Isolates of all species found in three smear ripened cheese varieties were tested with respect to changes in pH, proteolysis and aroma development. Most yeasts could be assigned to two groups. One group was characterised by the ability to ferment glucose, to utilise lactate and to increase pH values and by the fact that proteolytic activity was not shown. This resulted in alcoholic, acidic, fruity or fermented odours (Clavispora lusitaniae, Pichia jadinii and Williopsis californica). The second group was composed of non-fermenting species which utilised lactate, but the pH was not affected (Galactomyces geotrichum, Trichosporon ovoides and Yarrowia lipolytica). These yeasts were proteolytic yielding a cheesy aroma. Debaryomyces hansenii B comprised characteristics of both groups. (C) 1999 Elsevier Science Ltd. All rights reserved.