Comparison of the skin resistance of several grape varieties in relation to their physico-chemical properties

Abstract

Context and purpose of the study – The purpose of this study is to compare the skin resistance (SR) of the grapes with physico-chemical propertiess using a stong dataset and multidimentional statistical analysis .

A recent study has shown the role skin resistance plays against pest invasion but skin resistance could be a useful agronomic parameter, for example in the choice of the type of winemaking, by influencing the quantity of juice during crushing and maceration.

Material and methods – In this study we have used a hundred samples belonging to different vineyards of south of France (Aude) totaling twelve different grape varieties: Cinsault, Petite Arvine, Bourboulenc, Syrah, Carignan,  Viognier, Cabernet Franc, Mauzac, Mourvedre , Merlot, Grenache N and  Marselan.  Each sample consists of fifty berries. For each berry of a sample, a skin resistance test was carried out (Penelaup Robot). For each sample twenty four physico-chimical variables were measured with traditional methods (Dubernet Laboratories):  citric acid, gluconic acid, malic acid, tartric acid,   total acidity, volatile acidity IRTF, amino nitrogen ,  ammoniacal nitrogen IRTF, assimilable nitrogen IRTF, calcium, copper, delta C13 IRTF, iron, glucose + fructose IRTF, glycerol IRTF, magnesium, manganese, volumic mass IRTF, phosphorus, potassium, sodium, % Vol IRTF, zinc and pH IRTF.

Results – Thanks to our strong dataset, the results of this work demonstrate firstly a significant difference of the skin resistance depending on the grape variety and secondly that the skin resistance is a single parameter which cannot be directly explained by other physico-chemical variables.

We plan to complement the dataset with sensory analysis of the corresponding wines for each sample.