Changes in Constituents during the Growth of Saccharomyces servazzii and Debaryomyces hansenii

Abstract

Changes in pH, and ethanol and reducing sugar contents during the growth of Saccharomyces servazzii and Debaryomyces hansenii in YM broth (yeast and malt extract) were studied under two different fermentation conditions; fermentation in air and fermentation in an atmosphere composed of 2% oxygen and 98% nitrogen gas. In addition, volatile constituents released in the head space gas by S. servazzii were analyzed by gas chromatography and mass spectrometry. During the fermentation, reducing sugar was utilized by the growing yeasts, the pH of the broth dropped and ethanol was formed. However, ethanol production by D. hansenii was low. The growth of both yeasts was faster in the fermentation in air than that in the artificial gas containing 2% oxygen. As the fermentation advanced, pH of growing broth of D. hansenii rose slowly. In the early stages of the fermentation, the growth of S. servazzii was faster than that of D. hansenii. In the advanced stage, however, cell number of D. hansenii excelled that of S. servazzii. Volatile constituents released during growth of S. servazzii were mainly composed of acetaldehyde, ethyl acetate, ethanol, n-propanol, iso-amyl acetate and iso-amyl alcohol.