Improvement of post-harvest quality of Balady lime fruit with Aloe vera gel and tea tree oil against green mold disease caused by Penicillium digitatum

Abstract

Penicillium digitatum Sacc is a common postharvest pathogen affecting lime fruits. It causes significant losses in postharvest lime production. An emerging alternative to chemical control is the use of environmentally friendly such as edible and biodegradable films and packaging. The goal of the current study was to test different concentrations of Aloe vera gel (5, 15, 25, 50, 75, and 100% v/v), tea tree oil coating (0.5, 1, 2.5, 5, and 10% v/v), and their combination for controlling P. digitatum in vitro. The results revealed that specific concentrations of Aloe vera gel (75% and 100% v/v), tea tree oil (2.5, 5, and 10% v/v), and Aloe vera gel (25%) + tea tree oil (1%) v/v showed the highest inhibitory effect against the pathogen. The most effective concentrations of Aloe vera gel (75%), tea tree oil (2.5%), and Aloe vera gel (25%) + tea tree oil (1%) were evaluated against the green mold disease of lime under natural infection through storage period (0, 7, 14, 28 days). Compared to the control group, all edible layers demonstrated a significant delay and reduced in disease severity percentage throughout the storage periods. However, coating lime fruits with a combination of Aloe vera gel (25%) + tea tree oil (1%) successfully prevented the green mold disease of lime fruits over 28 days. The impact of these coatings was evaluated on lime fruit quality maintenance (weight loss, firmness, juice weight, total soluble solids, total acidity, pH, vitamin C, lipid peroxidation content, total phenols, total flavonoid, and total protein) over 28 days of storage during the 2021 and 2022 seasons. All treatments improved fruit quality through the storage period compared with untreated fruits. Treated lime fruits with Aloe vera gel (25%) + tea tree oil (1%) exhibited slight reductions in weight loss and juice weight compared to alternative treatments as an average of the two successive seasons. Simultaneously, this treatment improved fruit firmness, vitamin C levels, total phenols, total flavonoid, and total protein when contrasted with other treatments as an average of the two studied seasons. These findings show that the combination of Aloe vera gel and tea tree oil coatings enhances the shelf life and maintains the quality of lime fruits. They can also be used as an environmentally acceptable, chemical-free alternative treatment to preserve the postharvest quality of lime fruit.