Caratterizzazione microbiologica e chimico-fisica di bevande fermentate tailandesi (Fervida) prodotte a livello domestico in Italia. Microbial and physico-chemical characteristics of Thai fermented vegetables drinks (Fervida) of Italian domestic production

In recent years, the use of fermented drinks, called Fervida, obtained at home using three ingredients: a vegetable (fruit or vegetable, aromatic herb or root), water and a sweetener in proportion 3:5:1. is spreading in Italy. Fermentation is natural, probably produced by different microorganisms deriving from the ingredients. As there are no data at the moment, the aim of the work was to study the microbial and physico-chemical characteristics of these drinks. Fervida, ready to drink, were initially studied, produced with a basic sugar solution added with different vegetables (Oregano, Ginger, Red Rice, Citrus fruits plus Kiwi and Turmeric) and left to ferment for over an year at room temperature. Then it was studied the production process of two Fervida obtained with Oregano and Citrus + kiwi and the influence of the type of sugar (cane or beet) on the sensory quality of two Gala Apple Fervida, fermented for three months. The results showed that Fervida studied were produced following the activity in sequence of three different microbial groups: yeasts, lactic bacteria and acetic bacteria. This is demonstrated by the presence of a low pH (<3) and different aliquots of ethanol, lactic and acetic acid. The microorganisms were isolated and identified and belonged to the genera Saccharomyces, Zygosaccharomyces, Pichia, Gluconobacter and Lactobacillus. Yeasts predominate in the initial stages of fermentation, then they are replaced by lactic bacteria and finally by acetics. By prolonging the conservation, the organic acids produced (acetic and lactic acid) inactivate the microorganisms responsible for the production of these drinks.