Factors contributing to increased bruise expression in avocado (Persea americana M.) cv. 'Hass' fruit

Mesocarp bruising is an important postharvest problem of avocado fruit. Bruise expression may be influenced by inherent fruit characteristics, and pre-and postharvest handling practices and conditions. In this supply chain focused study, the putative effects on avocado cv. 'Hass' bruise expression and severity of fruit maturity, temporal duration before or after impact injury, fruit firmness, and fruit holding temperature were examined. Mesocarp bruising in ripening fruit decreased in a linear fashion with advancing fruit harvest maturity over 20 weeks. Bruise severity increased progressively in fruit kept for up to 5 weeks before impact injury and also for those kept for up to 7 days after injury. Hard green mature stage fruit did not express bruising at <= 100 cm drop height (similar to 1.36 J energy absorbed). However, softening, firm ripe, and soft ripe stage fruit impacted from 50 cm (similar to 0.8 J energy absorbed) developed progressively greater levels of bruising. Keeping fruit at temperatures of 2.5 degrees C and 5 degrees C as compared with 20 degrees C at the time of impact resulted in less bruise expression. Similarly, fruit kept at post-impact temperatures of 2.5 degrees C and 5 degrees C as compared with 7.5 degrees C, 10 degrees C, and 20 degrees C also resulted in less bruise expression. Fruit kept at 5 degrees C for the first 8 h after impact and then at 25 degrees C for 40 h developed less bruising than fruit kept at 25 degrees C for 8 h after impact and then at 5 degrees C for 40 h. Overall, it is proposed that harvesting fruit at >= 23% dry matter concentration, passing them quickly through the supply chain such that bruising has less time to express, and keeping the fruit 'at' or ` below' 5 degrees C in the supply chain could reduce bruise expression levels in ripening 'Hass' avocado fruit.