Iranian Journal of Horticultural Science

Iranian Journal of Horticultural Science

Effects of Different Phenylalanine Concentrations on Selected Physiological and Biochemical Characteristics of 'Dargazi' Pear Fruit during Cold Storage

Document Type : Full Paper

Authors
Kamal Amini Khoshalani 1
Hamid Hassanpour 1
Karim Mandahakki 2
1 Department of Horticultural Sciences, Faculty of Agriculture, Urmia University, Urmia, Iran.
2 Department of Horticultural Sciences. Faculty Agriculture. Urmia University. Urmia. Iran
10.22059/ijhs.2025.384005.2220
Abstract
Pear fruit has a relatively short postharvest life due to its susceptibility to mechanical damage, moisture loss, and rapid deterioration during storage and transportation. This study investigated the effects of different concentrations of the amino acid phenylalanine on the postharvest quality and storage life of 'Dargazi' pear fruit during cold storage at 0 ± 1°C and 90–95% relative humidity. The experiment was conducted as a factorial arrangement based on a completely randomized design with two factors: phenylalanine concentration (3 and 6 mM) and storage duration (30, 60, and 90 days), with three replications. Fruit firmness, weight loss, titratable acidity (TA), juice pH, ascorbic acid content, total soluble solids (TSS), total phenolic content, total flavonoid content, malondialdehyde (MDA), electrolyte leakage, and the activities of ascorbate peroxidase (APX), phenylalanine ammonia-lyase (PAL), glutathione reductase (GR), and polyphenol oxidase (PPO) were evaluated. The results showed that treatment with 6 mM phenylalanine was the most effective in maintaining fruit quality during cold storage. Compared with the control, this treatment increased fruit firmness by 14.5%while reducing MDA content and electrolyte leakage by 69.8% and 16.6%, respectively. In addition, 6 mM phenylalanine significantly increased the activities of APX, GR, and PAL by 23.09%, 37.74%, and 30.35%, respectively. Overall, phenylalanine treatment enhanced antioxidant capacity, stimulated antioxidant enzyme activities, suppressed oxidative damage, and reduced membrane lipid peroxidation, thereby improving the storage performance of 'Dargazi' pear fruit.
Keywords
antioxidant activity
electrolyte leakage
membrane lipid peroxidation
pear fruit
phenylalanine
postharvest storage
Subjects

Extended Abstract

Introduction

Pear (Pyrus communis L.) is a commercially important fruit because of its desirable flavor, attractive appearance, and high antioxidant capacity. However, its postharvest storage life is limited due to its susceptibility to mechanical injury, moisture loss, and rapid deterioration during transportation and storage. Mechanical damage sustained during harvesting and handling often results in irreversible changes in fruit appearance, texture, and marketability. Numerous compounds have been investigated to delay fruit ripening and senescence and thereby extend the postharvest life of horticultural crops. Although many of these compounds have shown promising results under laboratory conditions, only a limited number have been adopted commercially because of safety concerns and regulatory restrictions. Among these compounds, the amino acid phenylalanine, a precursor of the phenylpropanoid pathway, has attracted considerable attention because of its ability to enhance the biosynthesis of phenolic compounds and improve the antioxidant defense system in plants.

 

Materials and methods

    This study investigated the effects of different concentrations of phenylalanine on the postharvest quality and storage life of 'Dargazi' pear fruit during cold storage at 0 ± 1°C and 90–95% relative humidity. The experiment was conducted as a factorial arrangement based on a completely randomized design with two factors: phenylalanine concentration (3 and 6 mM) and storage duration (30, 60, and 90 days), with three replications. Fruit firmness, weight loss, titratable acidity (TA), juice pH, ascorbic acid content, total soluble solids (TSS), total phenolic content, total flavonoid content, malondialdehyde (MDA), electrolyte leakage, and the activities of ascorbate peroxidase (APX), phenylalanine ammonia-lyase (PAL), glutathione reductase (GR), and polyphenol oxidase (PPO) were determined.

 

Results and Discussion

     Phenylalanine treatment significantly improved the postharvest quality of 'Dargazi' pear fruit during cold storage, with the 6 mM treatment showing the greatest effectiveness. Compared with the control, fruit firmness increased by 14.5%, while malondialdehyde (MDA) content and electrolyte leakage decreased by 69.8% and 16.6%, respectively. Furthermore, treatment with 6 mM phenylalanine significantly enhanced the activities of ascorbate peroxidase, glutathione reductase, and phenylalanine ammonia-lyase by 23.09%, 37.74%, and 30.35%, respectively.

The enhanced antioxidant enzyme activities were accompanied by increased accumulation of phenolic compounds and flavonoids, indicating activation of the antioxidant defense system. Consequently, oxidative stress was alleviated through reduced free radical accumulation and lower membrane lipid peroxidation, thereby preserving membrane integrity and improving fruit quality during storage. These findings suggest that exogenous phenylalanine effectively delays postharvest deterioration by enhancing antioxidant metabolism and maintaining cellular integrity.

 

Conclusion

    Exogenous application of phenylalanine effectively improved the postharvest storage performance of 'Dargazi' pear fruit by reducing chilling-induced damage, membrane lipid peroxidation, and electrolyte leakage while enhancing both enzymatic and non-enzymatic antioxidant defense systems. Among the tested treatments, 6 mM phenylalanine was the most effective in preserving fruit quality and extending storage life. These results indicate that phenylalanine has considerable potential as a safe and practical postharvest treatment for improving the storage quality of pear fruit.

 

Author Contributions

Kamal Amini Khoshalani: Conceptualization, Investigation, Data curation. Hamid Hassanpour: Project administration, Supervision, Conceptualization, Methodology, Formal analysis, Validation, Discussion, Writing, review and editing. Karim Manda-Hakki: Formal analysis, Discussion, Writing.

 

Data Availability Statement

The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.

 

Acknowledgements 

We appreciate and thank all those who were with us in this project, especially the officials of Horticulture

Laboratory, Faculty of Agriculture, Urmia University.

 

Ethical considerations

Not applicable.

 

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.

منابع

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Iranian Journal of Horticultural Science
Volume 56, Issue 3
Summer 2025
Pages 401-422

  • Receive Date 25 October 2024
  • Revise Date 02 March 2025
  • Accept Date 19 April 2025