Microbial resources for improving the sustainability in oenology

Abstract

Sulphur dioxide has long been considered an irreplaceable additive due to its numerous significant positive effects during winemaking and beyond. However, the association between sulphur dioxide and health-related issues and the consequent awareness of consumers for products without synthetic additives has led to explore new ways to ensure the quality of wine. Moreover, the general increase of the wine pH related to climate change inevitably reduces the effectiveness of sulphur dioxide. The search for alternatives is becoming even more challenging as consumers’ preferences are increasingly leaning towards green consumerism, clean labelling and environmental sustainability. One of the proposed alternatives is bioprotection that consists in the inoculation in must or wine of selected microorganisms having specific activities, with the aim of replacing sulphur dioxide. Many studies have been focused on the antimicrobial activity of microorganisms, however, the available research regarding their antioxidant activity is certainly more limited. The aim of this study was to investigate the antioxidant effects of Metschnikowia pulcherrima and Lacticaseibacillus casei during the production of Pinot Grigio, with the former inoculated during pre-fermentative maceration and the latter at the end of alcoholic fermentation. In the control, 2 g/hL of sulphur dioxide were added during the pre-fermentative steps. The antioxidant effect of M. pulcherrima has been associated to its ability to consume oxygen very efficiently, reducing its availability for the oxidation processes. Regarding Lcb. casei N87, the strain used in this study has the capability to switch from fermentation to aerobic respiration metabolism when provided with heme and menaquinone. The effect of the growth of this strain under respiratory conditions has been advantageously studied in the production of Cheddar-type cheese, wheat sourdough fermentation and fermented sausages (Reale et al., 2016a,b; Camprini et al., 2023). At the end of fermentation, the amount of polyphenols was found to be similar in the two experimental conditions. However, during storage the samples inoculated with the bioprotective cultures presented a higher concentration of polyphenols, demonstrating the effectiveness of these strains in the protection of these potentially oxidizable compounds. This study shows that the use of bioprotective cultures coupled with respiration-based technology may be effectively exploited to protect must and wine from oxidation, allowing the reduction of the use of sulphur dioxide. However, further studies will be needed to investigate the effects of bioprotective cultures on other wine parameters and grape varieties associated with different winemaking processes.