Valorization of wine-making by-products for developing innovative fruit jellies

The attention to the environmental impact of industrial by-products, along with the development of new foods containing high levels of fibres, have become growing research topics. In the last years some food applications of grape skins (GS) have been investigated, nevertheless no study has been carried out on food products having a ‘gel-like’ structure. The aim of this study (which is part of the wider ‘AGER project 2010-2222’) was to acquire new knowledge on food applications of some wine-making by-products, interesting for their high fibre and antioxidants contents. GS were processed into powders and used for the production of innovative fruit jellies. Four different recipes were studied; for each one, the starting mixture (Mix), the concentrated mixture (Cmix), the fresh fruit jelly (t0) and the fruit jelly after 23h (t23) and 26h (t26) at 50°C were evaluated. The addition of GS determined a significant (P<0.05) increase in the antioxidant activity (around 160%; ferric ion reducing ability power assay) and total phenolic compounds (around 140%; Folin-Ciocalteu assay) of the jellies, evidencing clear nutritional advantages. The GS fruit jellies also exhibited a lower L* and a slightly higher b* and Chroma values. The texture of the samples was also investigated, by a penetration test. Small penetration peaks (F1 and F2) were detected for fresh jellies, while F1 and F2 were 4-6 times higher and well defined after 23h and 26h at 50°C. The GS incorporation thus clearly modified the micro- and macro-structure of the jellies, conveying both structuring and nutritional properties. This research showed that GS can be successfully used to develop innovative foods having a gel-structure, opening the possibility to use GS also in the confectionery industry. This new application could also contribute to reduce the environmental impact due to the accumulation of wine-making by-products.