Pomegranate arils ('Wonderful') tolerance to low O₂ stress during active modified atmosphere storage: based on real time respiration rate

Successful characterization of the relationship between the respiration rate (RR) and low O₂ limit (LOL) is critical for optimizing the modified atmosphere packaging (MAP). It is well documented that low O₂ atmosphere helps to reduce RR; however, it could lead to stress from the accumulation of end products from glycolysis. Therefore, the study investigated the response of pomegranate arils exposed to low O₂ atmosphere (2.5 kPa O₂ + 18 kPa CO₂ + 79.5 kPa NO₂) and identified the low O₂ limit at 5 and 10°C. The aim was achieved by using real-time RR data, respiration quotient (RQ) and tentatively identified volatile organic compounds (VOCs). Changes in VOCs were considered to determine either fermentative volatiles emitted due to the shift from aerobic to anaerobic respiration. The headspace gas evolution showed that, changes in gas composition were significantly affected by the storage temperature and storage duration, however, minimum change was observed at 5°C. Respiration quotient was 1.0 at 5°C, and a sharp increase of 3.0 was observed at 10°C. Response of the arils to low O₂ stress was observed with shifts in VOCs composition, especially those involved in anaerobiosis. Ethanol, acetaldehyde, and hydrazine, methyl-complexes were emitted under low O₂. Low O₂ tolerance limit at the studied temperatures was then estimated as 2.18-2.28 kPa at 5 and 10°C, respectively.