Evaluation of micro-perforated LDPE bags for reduction of postharvest moisture loss and shrivelling in Japanese plums

Plums produced in South Africa take up to eight weeks in shipping time to reach overseas markets. Significant weight loss and fruit with a shrivelled appearance is often a consequence of this extended shipping period. This leads to consignments being rejected, or requiring costly repacking, leading to significant financial losses for the industry. A range of HDPE and LDPE bags with different numbers of macro- and micro-perforations were evaluated for reduction of moisture loss and shrivelling on susceptible 'Laetitia', 'Sapphire' and 'African Delight™' plums from the Franschhoek growing area, during two consecutive seasons (2015/16 and 2016/17). Five treatment bags, with five replications/boxes treatment^-1, were evaluated for each cultivar. Compared to the HDPE macro-perforated shrivel sheet used currently, LDPE bags with micro-perforations (92, 72 and 4) decreased the fruit weight loss and shrivel in all cultivars, but only significantly in 'Sapphire'. 'Laetitia' and 'Sapphire' had a very low shrivel incidence in 2016/17 (3.54 and 6.82%), and even though the LDPE bags reduced shrivel incidence, no additional benefit was derived from using bags. 'African Delight™' had a higher shrivel incidence in season two (24%), and while the bags decreased the shrivel percentage by 22%, it was not reduced below the threshold value of 10%. LDPE bags with 72 micro-perforations could be a solution to reduce moisture loss and shrivelling in these plum cultivars, while maintaining fruit quality. LDPE bags with only 4 micro-perforations also reduced the moisture loss and shrivelling, but caused an increase in chilling injury.