New perspective for the use of citrus by-productus in food and nutraceutical industries

Abstract

Aim of the study: Citrus is the most produced tree fruit crop in the world. Almost 33% of the Citrus fruits are industrially processed for juice production, however, a great amount of Citrus wastes including peels, segment membrane and seeds are produced. Referring to the concept of circular economy, the present research project aimed to investigate a model for the reuse of C. × clementina Hort. by-products, in order to propose their utilization for the development of functional drink useful in prevention and treatment of prediabetes condition, hyperglycaemia and hyperlipidaemia. Materials and methods: The chemical profile of C. × clementina Hort. (Clementine di Calabria, PGI) juice and extracts was evaluated using HPLC-DAD and HPLC-UV. For determination of antioxidant activity four different in vitro tests (DPPH, ABTS, -carotene bleaching test and FRAP), were performed. The in vitro hypoglycaemic potential was tested by the inhibition of -amylase and -glucosidase enzymes. The lipase inhibitory activity was also assessed. Results: Juice obtained from fruits collected in Corigliano Calabro (JF) was characterized by a higher content of bioactive compounds with consequent higher bioactivity as confirmed by PCA. For this reason, JF was chosen as a matrix to be enriched with C. × clementina leaves and peel extracts. Hesperidin, tangeritin, sinensetin, and quercetin-O-glucoside were the most abundant constituents in all investigated samples. Considering that the content of coumarins is strictly regulated in foods, the absence of these phytochemicals represents an additional value for the potential industrial application of our samples. Among applied extraction techniques, ultrasound-assisted maceration resulted the most promising procedure to obtain extracts characterized by the highest of bioactivity in terms of antioxidant and enzymes inhibition. Indeed, leaves (from Corigliano Calabro) hydroalcoholic ultrasound-assisted maceration and peels (from Cetraro) ethanol ultrasound-assisted maceration were chosen as phytocomplex to be added to JF at different concentrations (20, 15, 10, and 5% w/v of extracts). Generally, the increase in phytochemicals content and bioactivities were significantly higher in juices enriched with leaves and leaves + peels (1:1) extracts. In order to estimate the effect of pasteurization process on our functional drink we have decided to pasteurize the 20% w/v enriched juice samples. As expected, the process decreased the bioactivity of samples in comparison to unpasteurized juice. Nevertheless, enrichment with Citrus by-products, especially with leaves extract, resulted in an increase of total phytochemicals content and bioactivity compared to the pasteurized control juice. Conclusion: On the basis of obtained data regarding the interesting bioactivity of enriched juices and comforted by sensory analysis data we can propose C. × clementina by-products as a promising source of bioactive compounds useful for formulation of functional drink or foods for preventing diseases associated to oxidative stress with particular reference to hyperglycaemia and hyperlipidaemia conditions. Moreover, the high antioxidant potential of these extract allows us to propose their use as food additives able to extent the shelf-life of different foods products. The obtained data encourage researchers to continue their work to assess the impact of functional juice on pathological models, and evaluated its bioaccessibility, bioavailability as well as possibility of hypovitaminoses due to fat reduction.