Implementing VIS-NIR spectroscopy as a rapid and non-intrusive technique for assessing anthocyanin and phenolic concentrations in Vitis vinifera L. Grenache whole grape berries

Wines made with grapes submitted to postharvest dehydration are often referred to as “passito” or “straw wines.” This distinct style of winemaking consists of a process of water loss that allows the berries to undergo a mild water stress and senescence process [1].

There is an urgent need in viticulture to adopt alternative herbicide-free soil management strategies to mitigate climate change, increase biodiversity, reduce plant protection products and improve soil quality while minimizing detrimental effects on grapevine’s stress tolerance and fruit quality. To propose sustainable solutions, adapted to different pedoclimatic conditions in Switzerland, we developed a multidisciplinary 4-year project, started in 2020. Objectives of the project are to a) evaluate the impact of green covers (spontaneous flora, winter cover crop and permanent ground cover) on environmental and agronomic parameters and b) develop subsequently innovative strategies for different viticultural contexts of Switzerland. The project is divided into 3 phases: 1) diagnosis, 2) on-farm and 3) on-station experiments. Phase 1) consisted in an assessment of 30 commercial vineyards all over Switzerland, where growers already use different herbicide-free soil management strategies. The most promising practices identified in this exploratory phase will be replicated in commercial vineyards across Switzerland (“on-farm”) as well as in a classical randomized block design in an experimental plot (“on-station”). For phase 1), measurements consisted in evaluation of soil status (compaction, structure, roots development), soil microbial diversity (metagenomics), plant diversity and biomass, vine physiology (water stress, vigor, leaf nitrogen) and berry quality (acidity, sugar, available nitrogen). Interestingly, the permanent ground cover resulted in a higher Shannon index thus a higher biodiversity as compared to the other itineraries. The winter cover crop increased vine nitrogen and vigor while deteriorating soil quality, leaving the soil more exposed and compacted likely due to more frequent tillage. The spontaneous flora led to higher berry sugar accumulation, less nitrogen and higher malic acid concentration putatively due to a higher water retention of the flora in a particularly wet vintage. Phases 2) and 3) are required to confirm those tendencies, over the 3 next vintages and different climatic conditions.

Methoxypyrazines (MPs) are readily extracted from grape berry and rachis during fermentation and can impart “green” and “herbaceous” sensory attributes to wine. Irrespective of whether MPs, including 3-isobutyl-2-methoxypyrazine (IBMP), 3-isopropyl-2-methoxypyrazine (IPMP), and 3-sec-butyl-2-methoxypyrazine (SBMP), are extracted from berry or other vine material, techniques for remediation of wine with overpowering sensory characters attributable to MPs suffer from poor specificity or produce undesirable sensory outcomes, meaning that alternative control approaches are needed.

Dans les Charentes, en réponse à une crise de production du vignoble destiné à la production de Cognac, un plan de diversification viticole pour des vins de pays de qualité est mis en place. Il nécessite une connaissance des sols et de leurs caractéristiques viticoles pour orienter le choix des types de vins et adapter l’itinéraire technique de production.

Pressing has a relevant impact on the characteristics of the must and subsequently on white wines produced [1]. Therefore, the adequate management of pressing can lead to the desired extraction of phenols and other grape compounds (i.e. Organic acids), aromas and their precursors, allowing the production of balanced wines [2]. This aspect is especially important to sparkling wine where the acidity and pH, and the content of phenols affect its longevity and the expected sensory character.