South Africa Wine Technical Yearbook 2025

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FIGURE 1. Main analytical parameters of the final FX10 , XAROM , KLIMA and OMEGA + KLIMA wines (dry wines post-MLF).

most S. cerevisiae strains in terms of ethanol yield and acidity modulation, resulted in the lowest lactic acid levels. In XAROM and KLIMA wines, higher lactic acid was associated with their ability to preserve/produce malic acid during AF, resulting in greater lactic acid levels post-MLF. In these strains, malic acid is produced from grape sugars, contributing to lower ethanol content. In the OMEGA + KLIMA treatment, the additional quantity of lactic acid (0.6 - 0.8 g/L) originated from L. thermotolerans metabolism of sugars, further decreasing ethanol and enhancing bioacidification.

The control treatment, FX10, had higher ethanol levels than both XAROM and KLIMA (Figure 1A), while the lowest ethanol content (< 0.5 % vol) was found in OMEGA + KLIMA co-inoculations. FX10 also showed the highest pH across both harvests (4.0), whereas pH values in the other wines were up to 0.2 units lower (Figure 1B). The TA of wines showed inverse trends; the lowest values in FX10, and the highest in OMEGA + KLIMA wines (Figure 1C). These differences were linked to variations in lactic acid concentration post-MLF (Figure 1D). FX10, representative of

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TECHNICAL YEARBOOK 2025