Short-term gaseous treatments preserve firmness and fruit quality in raspberries stored at low temperature: Impact on the expression of cell wall remodeling genes.

Short-term gaseous treatments with 15 % and 20 % CO2 for 2.5 d were analyzed for their effects on the quality of Regina raspberries from two harvest dates (June and September) and stored at 1 °C. The study examined key quality attributes, including titratable acidity, soluble solids content, pH, weight loss, total decay, and fruit mechanical properties. Additionally, oxidative stress markers like malondialdehyde and hydrogen peroxide were assessed, along with the expression of genes associated with cell wall modification, including EXP4, EXP12, XTH9, XTH22, PL4, PL20, PG, PE1 and PE3. The results indicated that low-temperature storage under atmospheric conditions led to an increase in the maturation index, along with total decay, increased oxidative stress markers, and loss of firmness. Both gaseous treatments positively influenced these parameters. In June-harvested raspberries, both treatments reduced the oxidative stress markers and total decay, while 20 % CO2 enhanced mechanical properties and reduced maturation index levels. In contrast, in September-harvested fruit, both CO2 treatments were more effective in controlling oxidative stress, total decay, weight loss and the increase in maturation index, while also maintaining mechanical integrity. The analysis of gene expression showed that short-term gaseous treatments affected the regulation of cell wall-related genes, delaying or preventing the increase in PG, PE1 and EXP4, which are associated with fruit softening, regardless of the harvest date. These findings suggest that short-term CO2 treatments present a promising approach for preserving the quality of raspberries during storage, improving both their physical and biochemical properties.