AGRESTO FROM UNRIPE ORGANIC GRAPE WITH ANTIMICROBIAL ACTIVITY

Agresto is a seasoning obtained from unripe grape used with different food including vegetables and meat preparations. The characteristic sour note in this case is not due to the acetic acid but to other organic acids, mainly malic and tartaric. In Tuscany the interest of consumers stimulated the development of an experimental project to produce Agresto in the specific area of Amiata Mountain, with the aim of affirming the territorial specificities of a natural product derived from unripe grapes, obtained from local grapevine varieties, to enhance its use in gastronomy. Agresto samples were obtained following an ancient recipe from different Vitis vinifera varieties, including Sangiovese vines and local grape varieties grown in an ampelographic collection located in Cinigiano (Grosseto, Italy) and cultivated according to the organic farming method. Sensorial analysis on the different types of Agresto obtained was also performed. Agresto has been also examined for its beneficial properties related to its origin from grape and to the method of production. Tuscan Agresto is currently marketed in very modest amounts especially in “short chain” as a niche product although its use could expand. Chemical and microbial characterization of Agresto’s samples of different origins showed notable antioxidant properties, antiradical activity, and total polyphenol content. Chemical analysis of Agresto samples indicate elevated contents of organic acids, total phenols and catechins, expressing also specific sensory profiles. All samples have a good antiradical activity, with values ranging from 75 to 89%. This activity is higher than of Trolox, an analogue of vitamin E. The analysis of total polyphenol content (TPC) indicate that Agresto samples contained about 45 -50 mg GAE/ml of polyphenols. The antiradical activity of Agresto correlates with polyphenol content, suggesting to consider this product as a potential functional food. In order to obtain a deeper knowledge on Agresto's beneficial properties, its possible antimicrobial activity has been evaluated on Gram negative (Escherichia coli, Enterobacter aerogenes, Salmonella typhimurium) and Gram positive (Enterococcus faecalis, Staphylococcus aureus) bacterial strains, and the MIC (minimal inhibitory concentration) was determined. It was found growth inhibition of all the bacterial strains analyzed.