Quality and bioaccessibility of total phenols and antioxidant activity of calçots (Allium cepa L.) stored under controlled atmosphere conditions

Calçots are the floral stems of the second-year onion (Allium cepa L.) resprouts with economic importance in Spain, where they are usually consumed roasted. The effect of two controlled atmospheres (CA) of 2.0% O2 + 3.5% CO2 (CA1), 1.0% O2 + 2.0% CO2 (CA2) and air at 1 °C for 60 d on the physicochemical, nutritional and sensory quality of calçots were studied. In addition, the total phenolic content (TPC) and the antioxidant activity (AA) of roasted calçots were evaluated after an in vitro gastrointestinal (GI) digestion. Both CA regimes reduced the respiration rate of the stored product without causing physiological disorders. The TPC and AA of calçots increased during storage. Storage for 60 d in CA2 resulted in the highest AA by DPPH assay, whereas calçots stored in air for 60 d showed the highest TPC and AA by FRAP assay. Calçots stored in air for 30 d and fresh harvested sample presented the highest total flavonoids values. After 30 d of storage, calçots stored in CA had a higher liking degree than calçots stored in air. The AA of digested calçots decreased drastically after in vitro GI digestion in comparison to the non-digested samples. However, TPC increased after digestion. Roasted calçots stored in CA1 for 30 d showed the highest TPC and AA retention in the intestinal phase. CA could be a postharvest strategy for the storage of calçots.

This research was carried out with the financial support of ACCIÓ (Generalitat of Catalonia, RD14-1-004), ‘Cooperativa de Valls’, ‘Cooperativa de Cambrils’ and PGI ‘Calçot de Valls’. This work has been supported by the Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement (FI-DGR 2015) and CERCA Programme of Generalitat de Catalunya. Dr. Aguiló-Aguayo thanks to the Ministry of Economy and Competitiveness from the Spanish Government for the FPDI-2013-15583. Dr. Plaza thanks the National Institute for Agronomic Research (INIA) for a DOC-INIA research contract.