Dead pepper is one of the most challenging issues in chili pepper farming, causing significant economic losses to farmers in recent years. In some cases, entire fields have been abandoned, forcing growers to switch to other crops. Understanding the causes of dead trees and how to prevent them is crucial for sustainable production.
One of the main causes is the spread of disease through infected seeds. Seeds act as a primary carrier for long-distance transmission of pathogens and are often the initial source of infection in new fields. If not properly quarantined, these seeds can spread diseases across regions. Additionally, improper disinfection practices can create favorable conditions for pathogen development.
Post-harvest rot is another major issue in fruit production, leading to substantial losses worldwide. According to rough estimates, between 20% and 30% of fruits suffer from post-harvest rot, with China experiencing even higher rates—up to 30% to 40%. In tropical regions, where environmental conditions are ideal for disease growth, this rate can rise as high as 50%.
Heat treatment has become a popular method for preserving fruits after harvest. As concerns over chemical residues grow, researchers are increasingly turning to non-toxic, pesticide-free methods. Heat treatment is now widely studied and applied in various fruit preservation systems.
The basic concept of post-harvest heat treatment involves exposing fruits to controlled high temperatures for a set period. This process helps reduce physiological metabolism, delay ripening, and extend shelf life. Common techniques include hot water immersion, steam treatment, and hot air exposure.
The use of heat treatment in fruit preservation began in the early 20th century, initially aimed at controlling fruit rot. In 1922, Fawcett reported using heat to control orange rot caused by anthracnose. However, due to the rise of chemical treatments, heat treatment was largely abandoned for about 30 years. With increasing restrictions on chemical preservatives, interest in heat treatment has revived.
In 1953, Akamine et al. demonstrated that papaya could be treated with hot water at 44–49°C for 20 minutes to control anthracnose. Since the 1980s, China has adopted similar methods for mangoes and bananas. Studies by Liu Xiujuan showed that soaking mangoes in warm water (52–55°C) for 5–10 minutes significantly reduced decay, extending the preservation period to over 15 days without affecting color or flavor.
Research into the mechanisms of heat treatment has expanded over the past few decades. Scientists have found that heat can inhibit the activity of enzymes like polygalacturonase (PG), which contribute to fruit softening. It also affects ethylene production, a key hormone in fruit ripening. At higher temperatures, ethylene synthesis is suppressed, delaying ripening and improving storage quality.
Heat treatment also helps reduce the risk of post-harvest diseases by killing or inhibiting pathogens. For example, treating fruits at 55°C for over 30 minutes can effectively kill anthracnose mycelia, while 60°C for the same duration can eliminate spores. These findings highlight the importance of tailoring heat treatment parameters to specific fruits and pathogens.
Beyond its biological effects, heat treatment can also improve fruit quality by reducing physiological disorders such as cold injury and skin blemishes. By enhancing the fruit's resistance to stress, it supports better post-harvest performance and marketability.
Overall, heat treatment offers a promising, eco-friendly solution to the challenges of fruit preservation, combining effectiveness with minimal environmental impact.
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