Optimization of air-blast drying process for manufacturing Saccharomyces cerevisiae and non-Saccharomyces yeast as industrial wine starters

Sae-Byuk Lee, Won-Seok Choi, Hyun-Jung Jo, Soo-Hwan Yeo, Heui-Dong Park

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.