Bruise measurement of fresh market apples caused by repeated impacts using a pendulum method

This paper presented an approach using a pendulum method to measure bruise damage of apples to overcome the limitation of the drop test on impact control on a specific fruit zone. Conditions included three impact energies (0.011, 0.042, and 0.094 J) and four repeated series (1, 3, 5, and 10) across three surface zones (top/stem shoulder, middle/cheek, and bottom/calyx shoulder) on large and small fruit. A full factorial experimental design was performed to investigate the effects of these factors on bruise damage. Twelve smaller areas separated from each zone of a pair of large/small apples and twelve treatments between the three impact energies and four repeated impact series corresponded to each other to reduce errors caused by the variance of specimens. Impact parameters (impact force and contact time), bruised area (BA), volume (BV), and susceptibility (BS, the ratio of BV to impact energy) were counted/calculated, respectively. It was demonstrated that the apple surface zone and repeated impact series could significantly affect bruise sizes and susceptibility to bruising. Results indicated that the impact force clearly increased with increased impact series before five impacts, but the increment decreased successively for every single impact, and the same was true for BA and BV, while the contrary was true for BS. More repeated impacts with lower intensity were more likely to reduce BA and BV compared to fewer impacts with higher intensity. The contact time decreased from the top to the bottom zone at both 0.011 and 0.042 J impacts. The fruit zone near the stem was more susceptible to causing smaller bruise sizes at a 0.042 J impact.