High CO Reduces Spoilage Caused by in Strawberry Without Impairing Fruit Quality.

High CO (> 20 kPa) conditions are beneficial for suppressing spoilage caused by in strawberry fruit; however, these conditions are often accompanied by discoloration, off-flavors, and faster softening. Stepwise increments of CO concentrations have been proposed to alleviate injuries in fruits caused by high CO. In this study, we investigated whether stepwise increments of CO, up to 30 kPa and under a reduced O concentration, are beneficial for reducing fungal spoilage without inducing CO injury symptoms in strawberry fruit. Based on recommended settings (5-10 kPa O with 15-20 kPa CO), we first selected optimal O and CO concentrations that best-reduced spoilage caused by in red ripe "Sonsation" strawberry fruit. We found that higher O (10 kPa) and CO (20 kPa) concentrations were most beneficial for prolonging strawberry fruit shelf life. Subsequently, we studied the performance of red ripe "Arabella" strawberry fruit stored at 5°C under different controlled atmosphere (CA) conditions (10 kPa O with either 0, 20, or 30 kPa CO). The CO concentrations were achieved either within 8 h or in a stepwise manner within the first 4 days of storage. As a control, 21 kPa O and 0 kPa CO were used. Following storage for up to 11 days, the spoilage incidence was assessed at 12°C for 5 days. The application of high CO (20 and 30 kPa) combined with 10 kPa O greatly suppressed fruit spoilage during storage and subsequent shelf life. High CO suppressed respiration as well as maintained a higher pH and firmness in treated fruit. The level of total sugars did not change, but during storage, a substantial part of sucrose was converted into glucose and fructose, especially under high CO conditions. High CO did not affect ascorbic acid and anthocyanin levels. The stepwise increments of CO did not result in beneficial effects compared to the static application of high CO. Our results show that "Arabella" strawberry fruit are highly tolerant to elevated CO and can be stored under 30 kPa CO to prolong the shelf life.