Using hazelnut skin as a source od dietary fibre and antioxidant in fresh pasta.

Dietary fibre is the edible part of carbohydrates that cannot be digested but partially or totally fermented in the human intestine. Among dietary fibres cereal brans and whole grain rye are the principal ones used as additional ingredients in the production of pasta. Except for these dietary fibre sources, hazelnut skin obtained by brushing after roasting process is another source characterized by some phenolic compounds with antioxidant property as well as dietary fibre then it can be named antioxidant dietary fibre (AODF) (Saura-Calixto, 1998). Nowadays it is used as bedding for horses or as antioxidant source by pharmaceutic industry but it was not yet used by the food industry. Therefore the aim of this study was to evaluate the use of different percentage of hazelnut skins as an additional source of dietary fibre and antioxidant content in fresh pasta. Hence, four different skins from Tonda Gentile Trilobata (TGT), Tombul, San Giovanni and Georgia hazelnut varieties were used as replacement of the flour at three different percentage (5%, 10% and 15%) in the production of fresh pasta. The fresh pasta was subjected to the nutritional label and fibre content analyses to evaluate the possibility to use the claim “source of fibre” or “high in fibre” as reported by the Regulation (CE) 1924/2006. The fresh pasta was also subjected to the total phenolic content analysis (Folin-Ciocalteau method) and to the evaluation of the antioxidant capacity determined by using DPPH and ABTS methods. The cooked fresh pasta was also subjected to the texture and the sensory analyses. From the results obtained it was possible to underline that the claim “source of fibre” can be used for all the samples while the claim “high in fibre” only for those where the flour was substituted with an amount higher than 5%. Concerning the total phenolic content was observed an increase of the content, correlated to the addition of the hazelnut skin percentage. In particular, the fresh pasta made with the Georgia hazelnut skin was the sample with the highest total fenolic content in all the percentage used. Instead, after the cooking of pasta where the total phenolic content decreased, the pasta obtained by using the TGT hazelnut skin showed the highest content. Regarding the antioxidant capacity, the values increased in correlation with the percentage used. In particular, among the samples the pasta made with 15% of TGT hazelnut skin showed the highest value before and after the cooking process. The texture analyses underlined a decrease of the work value from the samples with 5% to 15% of hazelnut skin maybe due to the spherical obstruction of the hazelnut skin that led to the destruction of gluten reticulum. Instead the sensory analysis highlighted that among the fresh pasta tasted, the most appreciated by consumers were those made by using the 5% of hazelnut skin. The results obtained had shown, for the first time, that hazelnut skin could be used as ingredient in functional food with an appreciation by the consumer. Keywords: fresh pasta, hazelnut skin, dietary fibre, antioxidant capacity References: Saura-Calixto, F. (1998). Antioxidant dietary fiber product: A new concept and a potential food ingredient. Journal of Agricultural and Food Chemistry, 46, 4303-4306.