Deterioration in fruits and vegetables

[Virtual Presenter] The welcome message was about starting the lecture on the topic of "Deterioration in Fruits and Vegetables", which would cover the various factors contributing to the spoilage of these essential food items..

[Audio] The factors responsible for the deterioration of fruits and vegetables after harvesting include biological factors, such as microorganisms like bacteria and fungi, which cause damage to these perishable crops. Environmental factors also play a significant role in contributing to post-harvest losses..

[Audio] Fruits and vegetables are indeed cornerstones of a balanced diet, providing us with essential nutrients like vitamins, minerals, fiber, and antioxidants. These nutrients play a significant role in preventing chronic diseases such as heart diseases, diabetes, and cancer. In fact, the World Health Organization recommends consuming a minimum of 400 grams of fruits and vegetables daily to prevent these diseases..

[Audio] Despite their significance in human health, a substantial proportion of fruits and vegetables deteriorate before reaching consumers, resulting in waste and economic losses. Estimates suggest that approximately one-third of all produced food is wasted globally, with fruits and vegetables having the highest wastage rates of any food type.

[Audio] The concept of post-harvest deterioration dates back to the early 19th century, as scientists recognized that harvested fruits and vegetables were susceptible to spoilage. New techniques emerged in the early 20th century to extend the shelf life of produce, including cold storage, controlled atmosphere storage, vacuum storage, use of preservatives, sensor technology, nano-technology in packaging, coatings made from nanoparticles, and the application of artificial intelligence and machine learning algorithms..

[Audio] Biological factors significantly contribute to the deterioration of fruits and vegetables. Natural enzymes within the fruit can cause over-ripening or spoilage through enzymatic reactions. Insects can infest the exterior of the fruit, leading to faster decay and compromised quality. Diseases caused by viruses, bacteria, or fungi can result in rot and spoilage. The respiration rate of the fruit can impact its shelf life, with some fruits emitting ethylene gas that accelerates the ripening process. Any physical damage to the fruit can lead to faster deterioration due to microbial growth..

[Audio] The most significant biological process affecting the deterioration of harvested fruits and vegetables is the oxidative breakdown of complex materials into simpler compounds. This process involves the conversion of carbohydrates and acids into carbon dioxide, water, and heat, accompanied by the production of energy. As the stored food remains alive after harvesting, its living cells continue to respire to secure energy. This process is essential for the survival of the cells, but it also contributes to the deterioration of the fruit or vegetable..

[Audio] The respiratory quotient, or RQ, measures how much carbon dioxide is produced compared to the amount of oxygen consumed during cellular respiration. Many fruits store large amounts of organic acids in their vacuoles, which can be used as substrates in the citric acid cycle. When these acids are fully oxidized, they produce more carbon dioxide than oxygen, resulting in an RQ greater than one. Glucose, on the other hand, produces an equal amount of carbon dioxide and oxygen, yielding an RQ of one. Fatty acids, when oxidized, produce less carbon dioxide than oxygen, resulting in an RQ less than one..

[Audio] Fruits and vegetables can be classified based on their respiration rates into different categories. The classification ranges from very low to extremely high. The very low category includes nuts, dates, dry fruits, and vegetables, which have a respiration rate of less than 5 milligrams of carbon dioxide per kilogram per hour at 5 degrees Celsius. This group also includes commodities such as apple, citrus, grape, garlic, onion, and potato, which have a moderate respiration rate between 5 and 10 milligrams per kilogram per hour. The moderate category further divides into three subcategories: low, moderate, and high. The low category has a respiration rate between 5 and 10 milligrams per kilogram per hour, while the moderate category has a rate between 10 and 20 milligrams per kilogram per hour. The high category has a respiration rate above 20 milligrams per kilogram per hour. Finally, there are two extreme categories: very high and extremely high. The very high category has a respiration rate between 40 and 60 milligrams per kilogram per hour, while the extremely high category has a rate above 60 milligrams per kilogram per hour. These categories include commodities such as strawberry, raspberry, cauliflower, avocado, snapbean, green onion, Brussels sprouts, asparagus, broccoli, mushroom, pea, spinach, and sweet corn..

[Audio] Fruits and vegetables can be broadly categorized into two main categories when it comes to plant factors affecting their respiration. These categories include soluble sugars and the proportion of living cells..

[Audio] The water content of a product plays a crucial role in its respiration rate. Succulent products tend to have higher water contents, which means they respire more rapidly compared to non-succulent products. For example, lettuce heads with their high water content deteriorate faster than potatoes, sweet potatoes, or peppers with lower water contents. This difference in respiration rates can lead to varying degrees of spoilage and loss of quality..

[Audio] The concentration of oxygen and carbon dioxide plays a crucial role in determining the respiration rate of fruits and vegetables. When there is an increase in oxygen levels, the respiration rate also increases, and conversely, when oxygen levels decrease, the respiration rate slows down. Similarly, changes in temperature have a direct impact on the respiration rate. As temperature rises, the respiration rate increases, and as it falls, the respiration rate decreases..

[Audio] Transpiration is the primary reason behind the deterioration of fruits and vegetables. As a result, we experience direct quantitative losses, which manifest as a reduction in weight. Furthermore, transpiration leads to a decline in appearance, characterized by wilting and shriveling. Additionally, the texture of the produce deteriorates, resulting in softening and a loss of crispness. Moreover, transpiration also causes a loss in nutritional quality..

[Audio] Plant factors significantly influence the rate of transpiration in fruits and vegetables. The degree of tissue differentiation plays a crucial role in this process. Plants with highly differentiated tissues typically have lower water content compared to those with non-differentiated, succulent tissues. Under similar environmental conditions, tissues with higher water content lose water more quickly than those with lower water content. For example, asparagus and spinach exhibit high water content, whereas mature cabbage heads, onions, and celery display low water content due to their highly differentiated tissues. This difference in tissue structure affects the rate of transpiration, resulting in varying losses of water from different plant products..

[Audio] Well-developed and non-injured periderm loss water less rapidly and keep longer in storage than those products with a poorly developed or badly injured or bruised periderm. The outer cover of fruits and vegetables, also known as the epidermis and periderm, plays a crucial role in protecting them from external factors. The epidermis, which is a single layer of living cells, helps to regulate transpiration, or water loss, through the skin. This is achieved through the presence of a waxy layer on the epidermis, which slows down transpiration. Furthermore, plant products with cutinized epidermis tend to shrink less rapidly during storage compared to those with non-cutinized epidermis. This highlights the importance of the outer cover in maintaining the integrity and freshness of fruits and vegetables..

[Audio] Fruits and vegetables have an outer covering called the periderm, which helps to reduce water loss and keeps the product fresh for a longer period if it is well developed and non-injured. On the other hand, a poorly developed or badly injured or bruised periderm allows water to escape more quickly, resulting in a shorter shelf life. The periderm plays a crucial role in protecting the inner tissues of the fruit or vegetable from external factors like moisture, temperature, and light. Apples, pears, citrus fruits, root vegetables, potatoes, and sweet potatoes all have a periderm that serves this purpose. By understanding the importance of the periderm, we can better appreciate how it impacts the storage and handling of these perishable commodities..

[Audio] Temperature plays a significant role in inducing a higher rate of transpiration and shrinkage in stored fruits and vegetables compared to lower temperatures. This means that if the storage temperature is high, the produce will lose more water through transpiration, leading to shrinkage and potential damage. On the other hand, low temperatures tend to slow down this process..

[Audio] Ethene, or more commonly known as ethylene, is a colorless gas with a sweetish odor and taste. It's a highly reactive substance, exhibiting asphyxiating and anaesthetic properties, and is even flammable. But what's truly remarkable about ethylene is its impact on crops. It's been found to have physiological effects on plants, and was first identified as a volatile chemical produced by ripening apples back in 1934. Interestingly, all fruits produce small amounts of ethylene during their development. However, climacteric fruits those that undergo a rapid ripening process produce significantly more ethylene than non-climacteric fruits. And there's a specific threshold level of ethylene required to induce ripening, which is surprisingly low at just 0.001 micro litres..

[Audio] Fruits and vegetables exhibit varying levels of ethylene sensitivity, which affects their rate of ripening and spoilage. This classification system categorizes commodities based on their ethylene production rates at 20 degrees Celsius. The very low category includes products such as asparagus, cherry, and strawberry, which produce less than 0.1 milliliters of ethylene per kilogram per hour. These fruits tend to have longer shelf lives and are more resistant to spoilage. On the other hand, very high ethylene producers like passion fruit, sapota, and cherimoya have shorter shelf lives and are more prone to rapid ripening and spoilage..

[Audio] Ethylene plays a crucial role in the ripening process of certain fruits. It binds to specific receptors, forming a complex with copper, which ultimately triggers ripening. Interestingly, ethylene concentrations tend to rise before the onset of ripening, particularly in fruits such as bananas, tomatoes, and honeydew melons. This phenomenon is often referred to as the initial respiratory increase. On the other hand, ethylene levels do not typically rise before the increase in respiration in fruits like apples, avocados, and mangos..

[Audio] Ethylene plays a crucial role in various physiological processes in plants, including ripening, flavor development, and color formation in fruits. Its effects vary depending on the type of plant tissue and the levels of oxygen and carbon dioxide present. Moreover, ethylene is involved in several other biological processes such as disease tolerance, chilling injury, sprouting, growth, texture modification, respiration, nutrient content changes, abscission, senescence, and toxin formation. Interestingly, ethylene can cause de-greening in certain fruits like bananas and oranges, and it can bleach the green color of leafy vegetables like celery, cabbage, and broccoli. As an initiator or contributor to the ripening process, ethylene's impact on plant physiology cannot be overstated..

[Audio] Ethylene is a natural plant hormone that plays a significant role in the ripening process of fruits and vegetables. To control ethylene production, we have several options available. One method is to absorb it using materials such as activated charcoal, activated carbon, hydrated aluminum silicate, or zeolite. This can be done by placing these materials in the storage room where the produce is kept. Another approach is.

[Audio] Mechanical damage is one type of deterioration that can occur in fruits and vegetables. This type of damage is caused by physical forces, such as rubbing, vibration, dropping, or compression, during handling and transportation. There are three main types of mechanical damage that can occur. Firstly, roller bruising can occur when fruits and vegetables rub against each other or against a surface during handling and transportation. This can cause damage to the surface of the produce. Secondly, impact bruising can occur when products fall onto a hard surface during filling and handling of packages. Although this damage may not be visible on the surface of the produce, symptoms can appear internally. Finally, compression bruising can occur when fruits and vegetables are squeezed into a smaller space, causing damage to the produce..

[Audio] Physiological breakdown occurs when produce is exposed to an undesirable temperature. This can result in various types of injuries, including freezing injury, chilling injury, heat injury, and very low oxygen atmospheres. Freezing injury occurs when a commodity is stored at a temperature below its freezing point, while chilling injury occurs when it is stored at a temperature below its optimal storage temperature. Heat injury, on the other hand, results from exposure to direct sunlight or extremely high temperatures. These conditions can cause defects such as sunburn, bleaching, scalding, uneven ripening, and excessive softening. Additionally, very low oxygen atmospheres during storage can also cause physiological problems, leading to loss of texture, structure, and microbial damage..

[Audio] Fruits and vegetables are prone to pathological breakdown, which is the most frequent indication of deterioration. This phenomenon is primarily triggered by the actions of microorganisms such as bacteria and fungi, including yeast and mold. The juicy nature of these products renders them vulnerable to invasion by these organisms. Several fungi, such as Alternaria, Botrytis, Diplodia, Phomopsis, Rhizopus, Penicillium, and Fusarium, as well as bacteria like Erwinia and Pseudomonas, are notorious for causing substantial harm. Although microorganisms might consume limited quantities of food, they frequently damage the produce to the extent that it becomes unacceptable due to rotting or other imperfections. This can result in both a reduction in quantity and quality. When decay penetrates deeply into the product, it becomes unusable, whereas superficial damage can lead to skin blemishes that decrease the value of a commercial crop..