Abstract
Wine yeast (Saccharomyces cerevisiae D8) and non-Saccharomyces wine yeasts (Hanseniaspora uvarum S6 and Issatchenkia orientalis KMBL5774) were studied using air-blast drying instead of the conventional drying methods (such as freeze and spray drying). Skim milk—a widely used protective agent—was used and in all strains, the highest viabilities following air-blast drying were obtained using 10% skim milk. Four excipients (wheat flour, nuruk, artichoke powder, and lactomil) were evaluated as protective agents for yeast strains during air-blast drying. Our results showed that 7 g lactomil was the best excipient in terms of drying time, powder form, and the survival rate of the yeast in the final product. Finally, 7 types of sugars were investigated to improve the survival rate of air-blast dried yeast cells: 10% trehalose, 10% sucrose, and 10% glucose had the highest survival rate of 97.54, 92.59, and 79.49% for S. cerevisiae D8, H. uvarum S6, and I. orientalis KMBL5774, respectively. After 3 months of storage, S. cerevisiae D8 and H. uvarum S6 demonstrated good survival rates (making them suitable for use as starters), whereas the survival rate of I. orientalis KMBL5774 decreased considerably compared to the other strains. Air-blast dried S. cerevisiae D8 and H. uvarum S6 showed metabolic activities similar to those of non-dried yeast cells, regardless of the storage period. Air-blast dried I. orientalis KMBL5774 showed a noticeable decrease in its ability to decompose malic acid after 3 months of storage at 4 °C.
Highlights
Wine is one of the oldest fermented foods in history and is produced as a result of complicated interplay between the metabolic reactions of various microorganisms such as yeast and lactic acid bacteria (Zagorc et al 2001)
5–10% skim milk solutions were mixed with centrifuged yeast cells and the mixed cells were air-blast dried at 37 °C for 2 h until dried cells were obtained in the appropriate powdered form
When 10% skim milk was mixed with the dried yeast cells, the viable count of S. cerevisiae D8, H. uvarum S6, and I. orientalis KMBL5774 increased to approximately 0.89, 0.71, and 1.03 log cfu mL−1, respectively
Summary
Wine is one of the oldest fermented foods in history and is produced as a result of complicated interplay between the metabolic reactions of various microorganisms such as yeast and lactic acid bacteria (Zagorc et al 2001). High malic acid content lowers the quality of Korean wine due to high acidity, which has resulted in the poor competitive value of indigenously manufactured wine against imported wine (Kim et al 1999; Lee et al 2016). For this reason, isolating and utilizing indigenous yeasts instead of imported yeast starters are necessary to make Korean wine competitive. Hong and Park (2013) described that wine fermented by H. uvarum S6 (previously SS6) showed slower fermentation rate but had higher organic acid content and sensory evaluation scores compared to wine fermented by S. cerevisiae W-3. Hong and Park (2013) described that wine fermented by H. uvarum S6 (previously SS6) showed slower fermentation rate but had higher organic acid content and sensory evaluation scores compared to wine fermented by S. cerevisiae W-3. Seo et al (2007) and Kim et al (2008) reported that I. orientalis KMBL5774 could degrade malic acid during alcohol fermentation, and co-fermentation with I. orientalis KMBL5774 and S. cerevisiae W-3 resulted in better color, flavor, and taste compared to the fermentation using only S. cerevisiae W-3
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