Natural wax coating mitigates chilling injury in plum fruits

Plum is one of the most important and widely cultivated fruit in the world, rich in anthocyanins, flavonoids, vitamins, minerals, and other nutrients that contribute to its appeal as a healthful fruit for humans.

Simultaneously, as the climacteric fruit, its harvest period typically occurs during the summer months.

Additionally, due to the vigorous respiratory metabolism at room temperature, the fruit is prone to spoilage.

Plum is a cold-sensitive fruit

Studies have demonstrated that low-temperature storage can prolong the freshness and quality of plums; however, being cold-sensitive fruits, and chilling injury symptoms such as browning and water-soaked or even pulp flocculence of the flesh may occur at inappropriate low temperatures, which can affect the quality and flavor. 

Low-temperature storage has been employed as an essential means to extend the freshness period of fruit, which is safe and effective with a long storage period. The study of the causes of chilling injury in fruit and how to reduce the occurrence of chilling injury has been the focus of postharvest research.

Causes of chilling injury

Chilling injury is frequently associated with abnormal physiological responses such as membrane damage, oxidative stress, and abnormal respiration in fruit.

Mitochondria are intricate and essential cellular organelles that generate reactive oxygen species (ROS). Damage to mitochondria can disrupt the balance of the antioxidant system, producing excessive superoxide anion and exacerbating the damage to the cell membrane.

Mitigation of chilling injury

Researchers frequently employ both physical in addition to chemical methods to mitigate and reduce chilling injury to fruit.

Studies have indicated that the utilization of exogenous hormones, such as melatonin and methyl jasmonate, in pre-harvest and post-harvest fruit, can effectively mitigate ROS production, slow down the onset of lipid peroxidation, and maintain the integrity of the cellular membranes and improve the cold tolerance of postharvest fruit, thus reducing the occurrence of chilling injury.

The use of physical measurements such as modified atmosphere storage and film treatment is also a method to reduce the symptoms of chilling injury. Its principle is to maintain the appearance quality of fruit and regulate fruit respiration through the formation of a protective layer, and as a barrier between the fruit and the atmospheric environment, to maintain a high activity of reactive oxygen scavenging enzymes in the fruit, and ultimately to reduce the incidence of chilling injury in the fruit. 

These studies advocate the enhancement of fruit membrane system resistance and the creation of a protective barrier for fruit as effective means to reduce the incidence of chilling injury in fruit.

The plant wax layer, a defense line

The plant wax layer is the primary line of defense between plants and the environment, which effectively preventing ultraviolet burns, pests, and microorganisms from invading but also protects plants from environmental stress.

The existence of the natural wax layer of the fruit itself plays a specific protective role during storage. There are variations in the composition and structure of the wax components of different species and varieties of plants, which creates differences in storage quality during postharvest storage, especially under low-temperature storage conditions.

The composition and structure of the wax layer can be altered, and this alteration affects weight loss and decay during storage (Yang et al., 2023). Overall, epidermal wax is a key determinants of fruit quality and storage performance.

Epidermal waxes and the occurrence of fruit chilling injury

However, no researches have been concentrated on the relationship between epidermal waxes and the occurrence of fruit chilling injury in plums.

Therefore, the present study was conducted to observe the epidermal morphology and organelle structure of the plum epidermis from the morphological point of view and to investigate the association between wax composition and chilling injury by using gas chromatography-mass spectrometry (GC-MS) to investigate the wax composition of the epidermis of the fruit.

The study aims to establish a theoretical foundation for addressing the industrial issue of the occurrence of chilling injury in postharvest low-temperature storage of plums.

Abstract

The occurrence of chilling injury is closely related to changes in wax. In this study, we investigated the relationship in plum fruit between wax presence (CK) and removal of epicuticular wax (REW) based on micromorphology and metabolomics.

The results showed that wax reduced the incidence of chilling injury in plum fruit and slowed down the rate of loss of fruit firmness, and that the abundant wax structure not only protected the epidermal cells but also inhibited high-intensity respiration of the fruit.

The correlation analysis between wax components and chilling injury illustrated that triterpene components were positively correlated with the occurrence of chilling injury.

In summary, the present study revealed that wax components were involved in regulating chilling injury in plums, which provides a research idea to delay and reduce the occurrence of chilling injury in plums.

Sources

Revealing the crucial role of cuticular wax components in postharvest chilling injury of plums (Prunus Salicina Lindl.)
Xuan Wan, Xin Lin, Yun Zhang, Dengcan Luo, Junsen Peng, Hua Huang, Xiaochun Ding & Xiaoqing Dong
Scientia Horticulturae Volume 338, 1 December 2024, 113843

Picture

Huerta del Corneja, Cultivo de ciruelas pasas
https://huertadelcorneja.com/cultivo-de-ciruelas-pasas/