Valorizzazione dei sottoprodotti dell'industria enologica: sostanze polifenoliche, la loro attività antiossidante e innovazione di prodotto (alimenti funzionali).

In this thesis of Doctorate various scientific aspects will be examined in order to answer at the following perspective: - to improve the extraction and the recovering of antioxidant compounds from vegetable by-products as the grape pomace; - to study the esterase activity in Saccharomyces cerevisiae which come from the grape pomace and find out the relationship with the polyphenols shapes esterificated of the same vegetable material; - to estimate in vitro the antioxidant and antimicrobial activity of a commercial extract with high level of catechine obtained from grape seeds; - to study and evaluate the feasibility to produce frozen functional bread, adding phenolic antioxidant substances with antiradical action obtained from the grape seeds. The vegetable by-products often are a cost for processing because they have to be disposed. The exploitation of these waste vegetables, as functional components added in the processed food, can represent now an important sector which could be improved. We can consider the thesis of Doctorate divided mainly in two parts: the first part of the thesis is related with the best choice of the vegetable by-product on which to estimate the presence of substances i. e. polyphenols which can have antioxidant effects. Besides, in the specific case of the grape pomace, if the normal microflora present on it with its enzymes, could modify the structure of polyphenols and increase their antioxidant properties. The obtained results show that the grape pomace, as it is or exhausted, of the grape variety "Raboso Piave" contain appreciable amounts of polyphenols with high antioxidant activity; also the results show that the combination of acidified water and ethanol seems to be the best solution, in economical point of view, as solvent to be use for extraction. The use of synthetic substrates such as esters of naphthol and fluorescein allowed us to characterize 9 yeast strain of Saccharomyces cerevisiae isolated from the grape pomace of grape variety "Prosecco" on the basis of their esterase activity. From the spectrophotometrical and eletrophoretical analysis of the cytoplasmic extracts appeared clear, with some exceptions, that doesn't exist important differences between the 9 yeast strains. These data represent a focal point for future investigations of the yeast esterase affinity with natural substrates, such as esterified anti-oxidants, and on the possible modification of their characteristics through in vitro and in vivo tests. In the second part of the thesis we used commercial extracts derived from vegetable by-products of the oenological industry like the grape seeds. This because our aim was to deep investigate on the antioxidant and antimicrobial potentialities of the phenolic molecules present on these substances, as well as the effects of their adding to a common food as the bread. Therefore, we employed extracts standardized in composition, microbiologically sure and of possible food use. The two tests in vitro, set upped and evaluated exactly with a commercial extract, evidenced that they can be useful in order to understand the potentialities and the limits of studied active compounds. The simplicity of the execution of the test on slab allows testing at the same time several extracts, facilitating the phase of initial selection. The in vitro assay with cultured bovine lymphocytes, even if it is needed other investigations, could represent the dynamic intracellular ratio between antioxidant and prooxidant activity and constitute an additional tool for the characterization of several antioxidants. In the case of the preparation of a functional food, the utilized methodology permitted us to obtain a frozen bread that contains phenolic substances, of which the antiradical activity remained unchanged also after 65 days of storage at -18°C. At the end of this period the frozen bread after cooking shows: good and "appetizing" taste, lightly golden colour; optimal consistency. The real feasibility of this process has been positively evaluated on pilot scale. Because actually the people is looking for the interactivity food-health, there is a growing demand from consumers of food that has the normal nutritive function and that can help the body against the daily stress too. In this respect the firm, which collaborated with us to realize the functional bread, is evaluating the possibility to insert this product in its trade business. The proposal of a new kind of functional frozen bread finds out the assumption in the general ascertainment that the application of the freezing at the bread is a technology in fast growing in the bakery sector. The success of this technology comes from the possibility that it offers to better programme the production timing of the firm. In short, the production of new functional frozen bread can surely constitute a new marketing instrument in the market's niche of functional products, widely diffuse at the level of GOD (Great Organized Distribution), and improve the nutritional characteristics of the diet also in fast-food restaurants. However, the healthy of the consumer has to be always more important than the economical interest and any healthy "asserting" has to be necessary supported by good scientific grounding.