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Roma tomatoes (`Sunoma') were hand-harvested at the mature-green color stage and treated with 100 μL·L-1 ethylene for 60 h at 20 °C and 90% RH. Tomatoes at breaker ripeness stage (<10% red coloration) were sorted by weight (about 100 g) and half of the fruits were treated with 1-methylcyclopropene (1-MCP; 1 μL·L-1 for 24 h at 22 °C). After 1-MCP treatment, individual fruits were subjected to double impacts over the marked locular surface with force equivalent to a 40-cm height drop using a pendulum impactor. In non-1-MCP treated fruit, impacts increased the maximum respiration rate by 27% (to 39.1 mL·kg-1 per h) and ethylene production by 24% (to 5.5 μL·kg-1 per h). Treatment with 1-MCP decreased relative production of both CO2 (56%) and ethylene (54%) over non-1-MCP treated fruit, while the ripening period (as measured by softening and color development) was extended 2.5 times, to about 8 d. Fruits treated with 1-MCP had increased TTA (about 40%; 0.58% citric acid equivalent), decreased pH (5%), and no difference in soluble solids content (3.7 °Brix); double impacts did not affect these values. Double impacts accelerated the onset of polygalacturonase (PG) activity by about 100% (to 99.8 mol·kg-1 per min*10-5 D-galacturonic acid) at day 6 over non-impacted control fruit. 1-MCP treatment delayed the onset of increased PG activity by 10 d over non-1-MCP treated fruit. Although 1-MCP alleviated the impact-induced increase in PG activity, PG activity recovered to rates similar to those of non-1-MCP treated fruit during the final 4 d of ripening.
Roma tomatoes (‘BHN 467’) were hand-harvested at mature-green color stage and treated with ethylene (100 μL·L−1 at 20 °C and 90% relative humidity) until reaching breaker (<10% red), pink (30%–60% red), or light-red ripeness stage (60%–90% red). Individual fruit at each ripeness stage were subjected to double impacts over the locule using a pendulum-impact device with a force equivalent to two 40-cm drops, followed by ripening at 20 °C. Fruit exhibited most noticeable increases in respiration and ethylene production within 1 hour and 1 day after impact, respectively. After 24 hours, respiration rates increased 40%–60% regardless of ripeness stage, while ethylene production in impacted breaker-stage fruit increased 3-fold (to 6.7 μL·kg−1·h−1). Fruit impacted at breaker stage softened 2 days earlier compared with non-impacted breaker fruit. Fruit impacted at all ripeness stages had higher electrolyte leakage and polygalacturonase (PG) activity during ripening than non-impacted fruit. After 6 days, electrolyte leakage in fruit impacted at light-red ripeness stage was 23% higher than non-impacted fruit; PG activity in breaker fruit increased 40% at 10 days over non-impacted fruit. No changes were observed for soluble solids content, total titratable acidity, pH, or sugar/acid ratio from impacts, independent of ripeness stage.