Search

Food industry produces a large amount of onion wastes. Due to the high amount of bioactive compounds in onion by-products an idea for their reuse, could be use them as source of high-value functional and health ingredients. In this study, outer dry layers of coppery onion "Ramata di Montoro" were used as source of bioactive compounds. Firstly, the chemical profile of secondary metabolites of exhaustive extract, obtained by ultrasound assisted extraction was established by UHPLC-UV-HRMS/MS analysis. Subsequently, the supercritical fluid extraction was used as alternative and green method to recover flavonoids from onion skin. Main parameters such as pressure, temperature and composition of solvent modifier were optimized in order to improve the extraction efficiency of SFE technique, by using a response surface Box-Behnken design., (Copyright © 2018 Elsevier Ltd. All rights reserved.) more...

This work reports preliminary results on the potential of a metal oxide sensor (MOS)-based electronic nose, as a non-destructive method to discriminate three "Tropea Red Onion" PGI ecotypes (TrT, TrMC and TrA) from each other and the common red onion (RO), which is usually used to counterfeit. The signals from the sensor array were processed using a canonical discriminant function analysis (DFA) pattern recognition technique. The DFA on onion samples showed a clear separation among the four onion groups with an overall correct classification rate (CR) of 97.5%. Onion flavour is closely linked to pungency and thus to the pyruvic acid content. The e-nose analysis results are in good agreement with pyruvic acid analysis. This work demonstrated that artificial olfactory systems have potential for use as an innovative, rapid and specific non-destructive technique, and may provide a method to protect food products against counterfeiting., (Copyright © 2013 Elsevier Ltd. All rights reserved.) more...

Food waste is a serious problem for food processing industries, especially when it represents a loss of a valuable source of nutrients and phytochemicals. Increasing consumer demand for processed food poses the problem of minimizing waste by conversion into useful products. In this regard, onion (Allium cepa) waste consisting mainly of onion skin is rich in bioactive phenolic compounds. Here, we characterized the flavonoid profiles and biological activities of onion skin wastes of two traditional varieties with protected geographical indication (PGI), the red "Rossa di Tropea" and the coppery "Ramata di Montoro", typically cultivated in a niche area in southern Italy. The phytochemical profiles of exhaustive extracts, characterized by ultra-high-performance liquid chromatography coupled with ultraviolet (UV) detection and high-resolution mass spectrometry, revealed that flavonols and anthocyanins were the characteristic metabolite classes of onion skins. Quercetin, quercetin glucosides and their dimer and trimer derivatives, and, among anthocyanins, cyanidin 3-glucoside, were the most abundant bioactive compounds. The potential of onion skins was evaluated by testing several biological activities: ABTS/oxygen radical absorbance capacity (ORAC) and in vitro alpha-glucosidase assays were performed to evaluate the antioxidant and anti-diabetic properties of the extracts and of their main compounds, respectively, and proliferative activity was evaluated by MTT assay on human fibroblasts. In the present study, by observing various biological properties of "Rossa di Tropea" and "Ramata di Montoro" onion-dried skins, we clearly indicated that this agricultural waste can provide bioactive molecules for multiple applications, from industrial to nutraceutical and cosmetical sectors. [ABSTRACT FROM AUTHOR] more...