Bioscience Methods 2024, Vol.15, No.5, 207-215 http://bioscipublisher.com/index.php/bm 208 2 Post-Harvest Physiology of Loquat 2.1 Ripening process and physiological changes Loquat (Eriobotrya japonica Lindl.) is a non-climacteric fruit, meaning it does not continue to ripen significantly after being harvested. However, some cultivars exhibit ripening patterns similar to climacteric fruits, which complicates post-harvest management (Zhang et al., 2020). The ripening process in loquat involves several physiological changes, including a decrease in fruit firmness and an increase in sweetness and acidity balance, which are critical for consumer acceptance. During post-harvest storage, loquat fruit undergoes lignification, a process where lignin accumulates in the flesh, leading to increased firmness and reduced quality (Liu et al., 2019). This lignification is associated with the activities of enzymes such as phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD) (Cañete et al., 2015). 2.2 Key factors contributing to post-harvest losses Post-harvest losses in loquat are primarily due to mechanical damage, moisture loss, and decay caused by pathogens. Mechanical damage during harvesting and handling can lead to bruising, which accelerates deterioration. Moisture loss results in wilting, shriveling, and a decline in fruit texture and flavor, significantly reducing marketability. Pathogens such as anthracnose, canker, and purple spot are prevalent post-harvest diseases that contribute to decay and spoilage. Additionally, chilling injury (CI) during cold storage can cause browning and other disorders, further reducing the fruit's quality and shelf life (Lufu et al., 2020). 2.3 Sensitivity to external factors (temperature, humidity, etc.) Loquat fruit is highly sensitive to external factors such as temperature and humidity, which play crucial roles in its post-harvest physiology. Low-temperature storage is commonly used to extend shelf life, but it can also lead to chilling injury, characterized by lignification and browning of the flesh. Controlled atmosphere storage, hypobaric storage, and modified atmosphere packaging are some techniques used to mitigate these effects. High humidity levels can exacerbate moisture loss and decay, while optimal humidity conditions can help maintain fruit quality. The rate of respiration and ethylene production in loquat fruit is significantly influenced by storage temperature, with higher temperatures accelerating deterioration (Cai et al. 2006). Therefore, maintaining appropriate temperature and humidity levels is essential for minimizing post-harvest losses and preserving the quality of loquat fruit (Ding et al., 1988). 3 Traditional Post-Harvest Preservation Techniques 3.1 Cooling and cold storage Cold storage is a widely used method for preserving the quality of loquat fruit post-harvest. This technique helps in reducing the metabolic rate of the fruit, thereby slowing down the processes that lead to spoilage. However, loquat fruit is susceptible to chilling injury (CI), which can cause browning and other quality issues. Studies have shown that while cold storage can extend the shelf life of loquat, it can also lead to lignification of the flesh tissue, reducing the fruit's quality and economic value (Figure 1) (Zhang et al., 2022). To mitigate these effects, low-temperature conditioning (LTC) and heat treatments have been explored. These methods have been found to alleviate lignification and maintain the fruit's quality during storage (Su et al., 2023). Zhang et al. (2022) investigated the role of the antioxidant system in controlling reactive oxygen species (ROS) during the cold storage of loquat. The study highlighted the importance of enzymes such as superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX), among others, in mitigating ROS-induced chilling injuries. These enzymes work in concert to maintain redox balance and protect cellular structures by neutralizing ROS. Additionally, the involvement of the ascorbic acid-glutathione (AsA-GSH) cycle was noted, with components such as reduced and oxidized glutathione (GSH and GSSG) playing crucial roles. The interaction of these antioxidants helps prevent cellular damage, thus extending the shelf life of loquats under cold storage. The findings emphasize the significance of both enzymatic and non-enzymatic antioxidants in enhancing fruit resistance to cold-induced oxidative stress.
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