Food Microbiology

Kei-apple (Dovyalis caffra) is an evergreen tree indigenous to Southern Africa. The fruit contains high concentrations of L-malic acid, ascorbic acid, and phenolic acids. Kei-apple juice was sequentially inoculated with Schizosaccharomyces pombe and Saccharomyces cerevisiae yeasts. A reference fermentation using only S. cerevisiae was included. The fermentation was monitored by recording mass loss. At the end of fermentation, twelve untrained judges conducted free choice aroma profiling on the fruit wines. The kei-apple juice and wines were analyzed for total titratable acidity, total soluble solids, pH, alcohol, L-malic acid, and phenolic acids. Total titratable acidity was ca. 70% lower in Kei-apple wines produced with Sc. pombe+S. cerevisiae than in kei-apple juice. Kei-apple wines produced with Sc. pombe+S. cerevisiae showed substantially lower concentrations of L-malic acid than kei-apple wines produced with S. cerevisiae only. Wines produced with S. cerevisiae only proved higher in phenolic acid concentrations than wines produced with Sc. pombe+S. cerevisiae. Chlorogenic acid was the most abundant phenolic acid measured in the kei-apple wines, followed by protocatechuic acid. Judges described the kei-apple wines produced with Sc. pombe+S. cerevisiae as having noticeable off-odours, while wines produced with S. cerevisiae were described as fresh and fruity. Kei-apple wines (Sc. pombe+S. cerevisiae and S. cerevisiae) were of comparable vegetative and organic character. Saccharomyces cerevisiae produced kei-apple wine with increased caffeic, chlorogenic, protocatechuic, and sinapic acids, whereas Sc. pombe+S. cerevisiae produced kei-applewines with increased ferulic, and p-coumaric acids and low L-malic acid.