High-Temperature Semi-Dry and Sweet Low Alcohol Wine-Making Using Immobilized Kefir Culture

Low alcohol wines (≤10.5% vol) represent novel wine products steadily gaining the commercial market interest. Considering the technological advancements of immobilized systems in association with the drastic reduction of industrial operational costs in high-temperature wine-making in regions with tropical climate or hot summer periods, the aim of the present study was to assess the fermentation efficiency of both wet and freeze-dried immobilized kefir culture on natural supports in low alcohol wine production at high temperatures (>30 °C). Immobilized kefir culture was evaluated and compared to free cells in repeated batch fermentations for 3 months, indicating high operational stability, and found suitable for simultaneous alcoholic and malolactic low alcohol wine fermentation at temperatures up to 45 °C. High ethanol productivity [up to 55.3 g/(Ld)] and malic acid conversion rates (up to 71.6%), which could be adopted by the industrial sector, were recorded. Principal Component Analysis (PCA) revealed that the state of the cells rather than the nature of kefir culture affected significantly the content of minor volatiles determined by Head Space Solid-Phase Microextraction (HS-SPME) Gas Chromatography–Mass Spectrometry (GC/MS) analysis. Notably, all new products were of high quality and approved by the sensory panel. The results suggested a high industrial potential of the proposed technology in semi-dry low alcohol wine-making at 37 °C and in developing novel wine products with a sweet (liquoreux) character at 45 °C.