| چکیده انگلیسی مقاله |
Introduction Physalis (Physalis peruviana L.), commonly known as Cape gooseberry or ground cherry, is a valuable member of the Solanaceae family. It is cultivated as a perennial crop in tropical regions and as an annual in temperate climates. The fruit is a spherical berry that can be consumed fresh, dried, or processed into jams and desserts. Physalis fruits are rich in minerals, vitamins, and phytochemicals known for their anti-tumor and anti-inflammatory properties, contributing to their reputation as a "superfood." Globally, demand for this crop is increasing due to its health benefits, including in Iran, although comprehensive data on its cultivation within the country remains limited. As a climacteric fruit, Physalis has a very short postharvest shelf life—typically no more than five days—highlighting the need for safe and effective postharvest treatments to preserve quality and extend its marketability. To improve the storability and maintain the postharvest quality of physalis, researchers are exploring natural and safe treatment options. One such promising compound is melatonin, a pleiotropic molecule derived from tryptophan and endogenously synthesized in plant, animal, fungal, and prokaryotic cells. In plants, melatonin functions as a regulatory agent involved in numerous physiological processes, particularly in response to stress. It interacts with plant hormones and reactive species like hydrogen peroxide (H₂O₂), nitric oxide (NO), and hydrogen sulfide (H₂S), contributing to improved antioxidant activity, delayed senescence, and better stress tolerance. Thus, melatonin represents a promising and eco-friendly strategy to improve the shelf life, sensory quality, and marketability of physalis fruit. The aim of the present study was to improve the shelf life and postharvest quality of physalis fruits through melatonin treatment for distribution in local markets. Materials and Methods Fully orange-colored physalis fruits with completely yellow calyxes were harvested from a commercial greenhouse in Pasargad, Fars province. The fruits were quickly transported to the lab, visually evaluated, washed with deionized water, and air-dried. The experimental design was a factorial arrangement based on a completely randomized design (CRD), consisting of 12 treatments with three replicates per treatment (20 fruits per replicate). The experimental factors included fruit immersion in four levels of melatonin solution concentration (100, 200, and 300 µM, with distilled water as the control) and sampling time at three levels (7, 14, and 21 days of storage). Following the preparation of melatonin solutions at different concentrations, sixty fruits were immersed in each solution for five minutes. The treated fruits were air-dried for 30 minutes, then packaged in polyethylene bags with 3% perforation and stored at 10 °C under 90 ± 5% relative humidity for 21 days. Assessments were carried out at weekly intervals. Results and Discussion Overall, postharvest treatment with melatonin led to a reduction in respiration rate and polyphenol oxidase (PPO) activity in the juice, as well as an improvement or maintenance of skin carotenoid content, total soluble solids (TSS), titratable acidity (TA), ascorbic acid, total phenols, phenylalanine ammonia-lyase (PAL) enzyme activity, and total antioxidant activity in the juice. After 21 days of storage and at the end of the experiment, the assessment of all these attributes revealed that fruits treated with 300 μM melatonin were superior in terms of nutritional value, appearance, and postharvest oxidative stress response mechanisms compared to the other experimental groups. There was no significant difference in total soluble solids and titratable acidity among the fruits treated with different concentrations of melatonin; however, fruits treated with the two higher concentrations of melatonin showed the lowest respiration rate and the highest ascorbic acid content in the juice. Furthermore, fruits treated with 300 μM melatonin exhibited higher levels of total phenols, PAL enzyme activity, total antioxidant activity, and skin carotenoids compared to all other experimental groups, while also showing the lowest PPO enzyme activity. Conclusions Treating physalis fruits with exogenous melatonin, especially at concentration of 300 μM, can significantly enhance their postharvest quality and storability by modulating various physiological and biochemical processes. This approach has the potential to improve the marketability and economic value of harvested physalis as a high-value horticultural crop. |