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

Calcots are the floral stems of the second-year onion (Allison cepa L.) resprouts with economic importance in Spain, where they are usually consumed roasted. The effect of two controlled atmospheres (CA) of 2.0% O-2 + 3.5% CO2 (CA1), 1.0% O-2 + 2.0% CO2 (CA2) and air at 1 degrees C for 60 d on the physicochemical, nutritional and sensory quality of calcots were studied. In addition, the total phenolic content (TPC) and the antioxidant activity (AA) of roasted calcots 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 calcots increased during storage. Storage for 60 d in CA2 resulted in the highest AA by DPPH center dot assay, whereas calcots stored in air for 60 d showed the highest TPC and AA by FRAP assay. Calcots stored in air for 30 d and fresh harvested sample presented the highest total flavonoids values. After 30 d of storage, calcots stored in CA had a higher liking degree than calcots stored in air. The AA of digested calcots decreased drastically after in vitro GI digestion in comparison to the non-digested samples. However, TPC increased after digestion. Roasted calcots 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 calcots.