نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
In this study, the effect of preharvest application of arginine (0, 1, 2 and 3 mM), citric acid (0, 1, 2 and 3 mM), and their combined application on reducing chilling injury in ‘Meykhosh-e-Yazd’ pomegranate fruit was evaluated during cold storage at 4 ± 0.5 °C and 85–90% relative humidity for 120 days. The experiment was conducted on 10 year old Meykhosh pomegranate trees in a commercial orchard located in Ardakan, Yazd Province, Iran, using a randomized complete block design with three replications during the 2020 and 2021 growing seasons. The results showed that preharvest foliar application of arginine and citric acid had a significant effect on the qualitative attributes of pomegranate fruit. Arginine and citric acid treatments significantly increased vitamin C content (by 20–28%), titratable acidity (by 10%), total soluble solids (by 17–20%), and pH (by 10–15%). Conversely, arginine and citric acid significantly reduced electrolyte leakage (by 10–60%) and malondialdehyde content (by 15–20%) compared with the control, which may indicate an improvement in the integrity of fruit cell membranes. Among the treatments, 2 mM arginine, 3 mM citric acid, and the combination of 2 mM arginine + 3 mM citric acid showed better results for many of the evaluated traits. These findings confirm the beneficial role of arginine and citric acid in improving fruit quality and reducing chilling injury during storage of pomegranate fruit.
کلیدواژهها English
Extended Abstract
Introduction
Low-temperature storage is a critical postharvest strategy for preserving horticultural crops, effectively extending shelf life and maintaining nutraceutical quality. Pomegranate (Punica granatum L.), a fruit of high economic value endemic to subtropical climates, is highly susceptible to chilling injury (CI), which restricts the feasibility of cold storage. Extensive research has been conducted to mitigate CI using postharvest applications, including polyamines, salicyloyl chitosan, modified atmosphere packaging, 1-methylcyclopropene, and heat treatments. Recently, there has been growing interest in utilizing natural, eco-friendly compounds that are safe for both human consumption and the environment. Specifically, amino acids such as proline, phenylalanine, and arginine, alongside organic acids like oxalic, salicylic, cinnamic, and citric acid, have emerged as promising agents. Arginine, an essential amino acid, enhances tolerance to chilling stress by facilitating the biosynthesis of signaling molecules, such as polyamines, nitric oxide, proline, and agmatine. Citric acid, a weak organic acid, functions as an antioxidant that improves fruit yield and quality by neutralizing free radicals and serving as a precursor for the metabolic synthesis of arginine, proline, and thiamine.
Materials and Methods
This study was conducted as a factorial experiment in a randomized complete block design (RCBD) with three replications over two successive years. The experiment utilized 10-year-old pomegranate trees (cv. ‘Meykhosh’) located in a commercial orchard in Ardakan, Yazd, Iran. Foliar applications of arginine and citric acid (alone and in combination) were performed at three stages, at 20-day intervals prior to commercial harvest. The treatments included arginine (0, 1, 2, and 3 mM), citric acid (0, 1, 2, and 3 mM), and their combinations (Arg 1 mM + 1, 2, 3 mM CA; Arg 2 mM + 1, 2, 3 mM CA; and Arg 3 mM + 1, 2, 3 mM CA). Upon commercial maturity, fruits were harvested, transported to cold storage, and maintained at 4 ± 0.5 °C (85–90% RH) for 120 days. Biochemical indices, including total soluble solids (TSS), total titratable acidity (TA), pH, vitamin C (ascorbic acid), electrolyte leakage (EL) of arils and peel, and malondialdehyde (MDA) content of arils and peel, were evaluated.
Results and Discussion
Results indicated that while TSS content increased throughout the storage period, this increase was significantly suppressed in treated fruits. This rise in TSS during storage is likely attributed to fruit water loss or the breakdown of cell wall polysaccharides into simpler soluble sugars. Arginine and citric acid treatments attenuated this increase by reducing respiration rates and ethylene production. Similarly, vitamin C content declined during storage; however, the treatments mitigated this reduction by slowing metabolic processes. The pH of the fruit extract increased over time due to the respiration-driven degradation of organic acids; conversely, the applied treatments effectively maintained lower pH levels. TA content decreased throughout storage, with treated fruits exhibiting a slower rate of decline, highlighting a positive correlation between organic acid retention and treatment efficacy. Furthermore, MDA levels and EL increased during storage indicative of membrane damage but were significantly suppressed by the treatments. It appears these compounds inhibited lipid peroxidation of the cell membranes by neutralizing reactive oxygen species (ROS) and inhibiting lipoxygenase activity. Overall, arginine (2 mM), citric acid (3 mM), and their combination (Arg 2 mM + CA 3 mM) significantly reduced chilling injury compared to the control group.
Conclusion
The results demonstrate that postharvest biochemical and physiological degradation significantly diminishes the quality and marketability of pomegranate fruit during storage. The application of natural compounds, specifically arginine and citric acid, effectively preserved fruit quality by mitigating chilling injury and delaying senescence. These findings suggest that such treatments represent a sustainable and practical approach to enhancing the postharvest storage life of pomegranates.
Author Contributions
Zahra Sefidkouhi conceived and performed the experiments, and analyzed the data. M.A. Askari-Sarcheshmeh and M. Babalar supervised the research and provided scientific guidance. S.A. Salami acted as an advisor and provided expert feedback. E. Sadeghi assisted in the laboratory analyses. Zahra Sefidkouhi wrote the first draft of the manuscript. All authors contributed to the interpretation of the results, provided critical feedback, and reviewed and approved the final version of the manuscript.
Data Availability Statement
The authors declare that all the data supporting the findings of this research are available within the article.
Acknowledgment
This paper is published as a part of a PhD Thesis supported by the Faculty of Agriculture and Natural Resources, University of Tehran, Iran. The authors are thankful to the University of Tehran for providing the necessary facilities and supports.
Ethical considerations
This article does not contain any studies involving human and animal subjects.
Conflict of interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
