Physico-mechanical evaluation of the aptitude of berries of red wine grape varieties to resist the compression in carbonic maceration vinification

On the market there is an increasing interest of consumers in the wines produced by carbonic maceration technique. The peculiarity of these wines is owing to the chemical and physical phenomena related to the anaerobic metabolism that occurs in the uncrushed grapes under carbon dioxide atmosphere. To maximize these phenomena, high resistance of the grapes to splitting is required during the intracellular fermentation step. This work constitutes the first contribution to the evaluation of the varietal aptitude to resist the rupture under compression load. By texture analysis tests, twenty-three red winegrape varieties were studied, and the differentiating power of the mechanical variables of the whole berry and skin was assessed by univariate and multivariate analysis. The relationship among the instrumental berry hardness and other physical and mechanical properties was also investigated. Although all of the double compression parameters of the whole berry and the puncture ones of the skin contributed to the varietal differentiation, Principal Component Analysis highlighted that those of the whole berry showed higher discriminating power. The berry volume, skin break force and thickness, berry gumminess and springiness were positively correlated with the berry hardness, whereas the berry weight, skin break energy and Young’s modulus, berry cohesiveness, chewiness and resilience were negatively correlated. Furthermore, the skin break force and energy, and the berry cohesiveness and gumminess, were the more strongly and significantly correlated parameters with the berry hardness. The results obtained suggest that the manufacture of carbonic macerated wines should be planned considering the berry hardness, and it represents a new variable that should be considered in selecting which is the most appropriate winegrape variety to elaborate carbonic macerated wines.