Postharvest quality and pH of Fusarium inoculated redripe tomatoes stored under controlled atmospheres

Tomato (Lycopersicon esculentum Mill. cv. BHN 91) fruit were hand harvested at the pink stage of maturity and stored red-ripe at 12.5, 20, and 30°C in air, 3% O 2 + 5% CO 2 , and 0.5% O 2 + 20% CO 2 for up to 16 days. Half the fruit were inoculated with Fusarium solani. Control fruit retained the best appearance in 3% O 2 + 5% CO 2 at both 20 and 30°C. Inoculated fruit at 12.5, 20 and 30°C in air or 3% O 2 + 5% CO 2 remained acceptable for approximately 12, 3, and 2 days, respectively, but deteriorated more rapidly than those in 0.5% O 2 + 20% CO 2 as temperature and time increased. Off-odours were present in all 0.5% O 2 + 5% CO 2 treatments by days 12, 9, and 5 at 12.5, 20, and 30°C, respectively. Subjective evaluations tended to remain higher for 0.5% O 2 + 20% CO 2 even though internal firmness and physical integrity were inferior, and symptoms of anaerobiosis were presumed. A significant time- and temperature-dependent increase in pH of locular and pericarp tissue and supernatant pH occurred in inoculated regions of fruit held in air by day 12, 6 and 3 at 12.5, 20, and 30°C, respectively. In contrast, reduced acidity occurred at 9 and 5 days in 3% O 2 + 5% CO 2 at 20 and 30°C, respectively. Generally, increased pH followed a trend with air >3% O 2 + 5% CO 2 > 0.5% O 2 + 20% CO 2 . Titratable acidity in control fruit declined regardless of atmosphere when held at 12.5°C. Initial locule and supernatant pH was sufficiently low to be considered safe, but the pericarp pH of 4.63 approached the food safety threshold, and exceeded 4.7 with storage. Subsequently, food service establishments should beware of potential contamination when holding ripe fruit due to possible decay and metabiosis, anaerobiosis occurring in dressings, and decreased acidity with ripening.