Circular microbial biotechnology for improving colour and aroma in rosé wines produced in warm climates

Global rosé wine production is on the increase, but high temperatures in warm climates influence colour intensity and aromatic freshness, ultimately affecting sensory quality [1,2]. Applying non-Saccharomyces yeasts and lactic acid bacteria in combination with Saccharomyces cerevisiae in sequential inoculations offers a promising strategy to enhance colour expression and aromatic complexity during fermentation [3]. In this study, six pilot-scale fermentations (500 L each) were carried out using Nero d’Avola grape must, with co-inoculations of either Starmerella lactis-condensi MN412 or Candida oleophila YS209, with or without Lactiplantibacillus plantarum MLPKH45™, followed by sequential inoculation with S. cerevisiae NF213. Fermentation kinetics, microbial dynamics, CIELab colour parameters, and sensory profiles were monitored. Sequential inoculation accelerated fermentation compared to the control with S. cerevisiae, showing positive microbial interactions. All mixed fermentation trials showed significantly higher L values (up to 67.20 vs 57.67) and lower C values (17 vs 24.52), suggesting lighter hues and lower colour saturation. Total colour differences (ΔE) between treatments and the control reached up to 12.2, well above the visual perception threshold (ΔE > 2.7) [4]. Sensory analysis showed that sequential inoculations enhanced floral (up to 6.7) and red fruit notes (up to 6.5). The combination of C. oleophila YS209 + L. plantarum MLPKH45™, followed by S. cerevisiae, provided the best balance between colour intensity and sensory quality, achieving the highest overall score (7.5 vs 6.5 for the control). Overall, the results demonstrate that co-inoculation of non-Saccharomyces yeasts and lactic acid bacteria, coupled with sequential inoculation of S. cerevisiae, is an effective tool for modulating colour and aroma in rosé wines produced in warm climates. This approach supports more sustainable winemaking practices with reduced reliance on chemical additives.