Bruise damage susceptibility of pomegranates (Punica granatum, L.) and impact on fruit physiological response during short term storage

Bruise damage resulting from excessive impact and compression forces between the point of harvest and consumption is a major quality problem in fresh fruit marketing. This study investigated the susceptibility of three pomegranate (Punica granatum, L.) fruit cultivars (‘Acco’, ‘Herskawitz’ and ‘Wonderful’) to drop impact bruising. Impact threshold required to bruise fruit was investigated by determining the probability of bruise occurrence (PBO) from the population of the fruit of three pomegranate cultivars impacted at minimal drop heights (0.1, 0.15, 0.2 m). The effect of temperature on bruise susceptibility and fruit physiological response was studied by impacting fruit equilibrated at 5 and 20 °C from three higher impact (drop heights) levels above threshold (0.2, 0.4 and 0.6 m) followed by storage for 10 d to monitor fruit weight loss and respiration rate. Minimum drop impact level at which bruising was first observed and the associated PBO were 0.1 m (PBO; 0.44), 0.15 m (PBO; 0.5) and 0.15 m (PBO; 0.75) for ‘Wonderful’, ‘Herskawitz’ and ‘Acco’, respectively. ‘Wonderful’ pomegranate fruit had the lowest impact threshold, with the highest value of PBO (0.44) and lowest impact energy (371.87 mJ). Bruise susceptibility at higher impact levels above threshold (measured in bruise volume and bruise area) was cultivar dependent; in the order of ‘Wonderful’>‘Herskawitz’>‘Acco’. The measure of pomegranate fruit sensitivity to bruising measured as bruise susceptibility (mm³mJ⁻¹) and specific bruise susceptibility (mm³ mJ⁻¹ g⁻¹) that took into account the impact energy and fruit mass suggested that ‘Acco’ was the most sensitive cultivar to impact bruising followed by ‘Herskawitz’. Fruit stored in cold (5 °C) condition had larger bruise size (bruise volume and bruise area) than those stored at ambient (20 °C) temperature. Weight loss and respiratory activity were significantly reduced both in non-bruised control and bruised fruit stored in cold (5 °C) temperature. Conversely, at ambient storage, the highest respiration rate and percentage weight loss were recorded in bruised ‘Herskawitz’ and ‘Acco’ fruit, which increased with the level of impact bruising and storage temperature. These findings provide an evidence-based understanding of the bruise damage susceptibility of pomegranates and could be used to develop a postharvest handling tool for the investigated pomegranate cultivars.