Impact of gaseous ozone treatment on storability and quality of onion (Allium cepa L.) during bulk storage

Abstract

The increased storage life while maintaining the quality of the onion bulbs is crucial in the agriculture sector as it directly affects the marketability of the commodity. In the present investigation, gaseous ozone treatment was applied to a stored batch of 500 kg onion bulbs. During bulk onion storage, the fungal count increased from 4.28 ± 0.06 to 6.79 ± 0.23 log CFU/g, 2.86 ± 0.35 to 6.05 ± 0.12 log CFU/g and 2.87 ± 0.34 to 5.62 ± 0.27 log CFU/g, while the bacterial count increased from 1.90 ± 0.12 to 6.58 ± 0.32 log CFU/g, 1.15 ± 0.17 to 6.05 ± 0.18 log CFU/g and 1.19 ± 0.17 to 5.33 ± 0.04 log CFU/g for untreated, single-treated and periodically treated bulbs, respectively. This indicated that the ozone treatment controlled and reduced microbial count throughout storage. For a storage period of 120 days, periodic ozone treatment reduced rotting by 55.52 % compared to the untreated bulbs, while single treatment lowered rotting by 30.67 %. The change in pyruvic acid content with the storage period was significant for the treated and untreated bulbs. At the end of the storage period, it was found to be 12.61 ± 0.33 μmol/g F.W. for the untreated sample, 12.03 ± 0.60 μmol/g F.W. for the single treated sample, and 11.24 ± 1.01 μmol/g F.W. for periodically treated samples. Ascorbic acid content decreased with an increased storage period for all treatments, while phenols, flavonoids, anthocyanin content, and antioxidant activity increased significantly. Periodic ozone treatment is a viable fumigation method for extending shelf life and preserving bulb quality during storage.