The source of yeasts in New Zealand wines

Abstract

The source and nature of yeasts responsible for the natural fermentation of grape must in New Zealand have been examined. Kloeckera apiculata was the dominant species during the first stage of fermentation, but was later replaced by Saccharomyces cerevisiae, with lesser proportions of Saccharomyces chevalieri and Saccharomyces rosei. No fermenting yeasts were recovered from green grapes but most isolates from ripe grapes were of K. apiculata and S. cerevisiae. Tt was thought that the source of the fermenting species was the winery itself and previous season's pomace, in which they were found to be common; they were very rare in vineyard soil and were not recovered from fragments of bark and twigs of vines collected in winter. The vector by which fermenting species reached the ripening grapes was probably insects.