Deterioration in fruits and vegetables

[Virtual Presenter] Deterioration in fruits and vegetables is a major concern in the agricultural sector. Fresh produce is highly perishable and its quality can degrade rapidly after harvesting. In this presentation, we will explore the various factors responsible for this deterioration..

[Audio] By the end of this lecture, we will explore the various factors responsible for the deterioration of fruits and vegetables after harvesting. The role of biological factors in post-harvest damages will be examined, including the impact of microorganisms like bacteria and fungi on the quality and quantity of produce. Environmental factors that contribute to fruit and vegetable losses during post-harvest processing will also be discussed. Our learning objectives will provide a clear understanding of the key concepts and principles involved in maintaining the freshness and quality of fruits and vegetables throughout the supply chain.

[Audio] Fruits and vegetables provide essential nutrients like vitamins, minerals, fiber, and antioxidants, playing a significant role in preventing chronic diseases such as heart diseases, diabetes, and cancer. The World Health Organization recommends a minimum of 400 grams of fruits and vegetables per day for preventing chronic diseases..

[Audio] Despite their importance in human health, a significant portion of fruits and vegetables deteriorate before reaching consumers, leading to waste and economic losses. According to estimates, roughly one-third of all produced food is wasted globally, and fruits and vegetables have the highest wastage rates of any food type..

[Audio] The history of post-harvest deterioration dates back to the early 19th century when agricultural sciences first recognized that harvested fruits and vegetables were prone to spoilage. As industrialization progressed in the early 20th century, innovative solutions emerged to extend the shelf life of produce. These included 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. Enzymatic reactions within the fruit itself can cause over-ripening or spoilage. Insects can damage the exterior, leading to faster decay and compromised quality. Diseases caused by viruses, bacteria, or fungi can also lead to rot and spoilage. The rate at which a fruit breathes can affect its shelf life, while some fruits emit ethylene gas, which can accelerate the ripening process. Any physical damage can lead to faster deterioration due to microbial growth..

[Audio] Fruits and vegetables continue to respire even after they're harvested, using stored energy to break down complex materials into simpler compounds. This process releases carbon dioxide and water vapor, along with heat and usable energy..

[Audio] The respiratory quotient, or RQ, is a measure of how much carbon dioxide is produced compared to the amount of oxygen consumed during cellular respiration. In the case of many fruits, the vacuoles contain large stores of organic acids that can be used as substrates in the citric acid cycle. When these acids are completely oxidized, they produce more carbon dioxide than the amount of oxygen consumed. This results in an RQ greater than one..

[Audio] Fruits and vegetables can be classified based on their respiration rates. This classification helps us understand how quickly they break down after harvesting. The table shows different classes of respiration rates, ranging from very low to extremely high. We see that nuts, dates, and dry fruits have very low respiration rates, while asparagus, broccoli, and mushrooms have extremely high rates. This information is crucial in determining the shelf life of these commodities and planning their storage and transportation accordingly..

[Audio] Fruits and vegetables can be classified into two main categories based on plant factors affecting their respiration. These categories include environmental factors and plant factors themselves. Within the plant factors category, soluble sugars and the proportion of living cells are significant factors. Soluble sugars, particularly glucose, have a direct relationship with respiration, where the more soluble sugars present, the higher the rate of respiration. Additionally, the proportion of living cells also has a direct impact on respiration, as the more living cells there are, the greater the need for energy, leading to a higher rate of respiration. This is because living cells require a constant supply of energy, which respiration helps to liberate..

[Audio] The water content of a product plays a significant role in determining its respiration rate. Generally, the higher the water content, the faster the product will respire. Succulent products, which have a high water content, tend to respire more rapidly than non-succulent products. For instance, lettuce heads, which are highly succulent, degrade more quickly than potatoes, sweet potatoes, or peppers, which have lower water contents. This relationship between water content and respiration rate has important implications for the storage and handling of fruits and vegetables..

[Audio] Respiration rates can vary depending on two key environmental factors. The concentration of oxygen and carbon dioxide plays a crucial role in determining these rates. When there is more oxygen present, the respiration rate increases, whereas it slows down when there is less oxygen. This is because plants utilize oxygen as a source of energy during respiration. On the other hand, when there is more carbon dioxide, the respiration rate also increases. This is because plants release carbon dioxide as a byproduct of respiration..

[Audio] Transpiration is the main cause of deterioration in fruits and vegetables. As a result, we experience direct quantitative losses, which means a loss in weight. We also see a loss in appearance, with wilting and shriveling occurring. Furthermore, transpiration leads to textural quality loss, resulting in softening and a loss in crispness. Additionally, there is a loss in nutritional quality..

[Audio] Plant products differ in terms of tissue differentiation, which affects their ability to lose water through transpiration. Undifferentiated tissues with high water content generally tend to lose water more quickly than highly differentiated tissues with lower water content. For example, asparagus and spinach have high water content due to their undifferentiated nature, whereas mature cabbage heads, onions, and celery are examples of highly differentiated tissues with lower water content..

[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 periderm, consists of two main components: the epidermis and the periderm tissue. The epidermis is made up of a single layer of living cells, and it's covered with a layer of wax that helps to slow down transpiration. This means that plant products with cutinized epidermis tend to shrink less rapidly during storage compared to those with non-cutinized epidermis..

[Audio] Fruits and vegetables with well-developed and non-injured periderms tend to lose water more slowly and remain fresh for a longer period when stored compared to those with poorly developed, badly injured, or bruised periderms. The periderm serves as an outer covering for various types of fruits and vegetables, including apples, pears, citrus fruits, root vegetables, potatoes, and sweet potatoes..

[Audio] High storage temperatures induce a higher rate of transpiration and shrinkage in stored fruits and vegetables compared to lower temperatures. This results in more rapid water loss, leading to wilting and shrinkage. Conversely, low storage temperatures lead to slower rates of transpiration and less shrinkage..

[Audio] Ethene, or ethylene, is a colorless gas with a sweetish odor and taste. It's a highly reactive substance, having asphyxiant and anaesthetic properties, and is even flammable. This gas was first discovered in 1796. Interestingly, ethylene has been found to have physiological effects on crops, and its production was first identified in relation to ripening apples by Gane in 1934. While all fruits produce small amounts of ethylene during their development, climacteric fruits tend to produce significantly more of this gas than non-climacteric ones. Furthermore, research has shown that a threshold level of ethylene, measured at 0.001 micro litres, is required to induce ripening in these fruits..

[Audio] Fruits and vegetables differ significantly in their capacity to generate ethylene gas, which has a vital function in their ripening process. This classification system groups commodities based on their ethylene production rates, spanning from very low to very high levels. The table reveals that certain fruits like passion fruit, sapota, and cherimoya exhibit extremely high ethylene production rates, whereas others such as asparagus, cherry, and strawberry display very low rates. Recognizing these disparities is crucial for optimizing storage conditions and prolonging the shelf life of diverse fruits and vegetables..

[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. Ethylene concentrations tend to rise before the onset of ripening, particularly in fruits such as bananas, tomatoes, and honeydew melons. This phenomenon is characterized by an initial increase in respiratory activity. However, ethylene levels do not precede the increase in respiration in fruits like apples, avocados, and mangos..

[Audio] Ethylene plays a significant role in the ripening process of fruits. Its effects vary depending on the type of plant tissue and the levels of oxygen and carbon dioxide present. Not only does ethylene influence the ripening, flavor, and color formation of fruits, but it also contributes to disease tolerance, chilling injury, sprouting, growth, texture, respiration, nutrient content, abscission, senescence, and toxin formation in plants. Furthermore, ethylene causes the de-greening of bananas and oranges, as well as the bleaching of green colors in leafy vegetables like celery, cabbage, and broccoli. As an initiator of fruit ripening or a contributor to the ripening process, ethylene's impact 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 to destroy ethylene using potassium permanganate, which is a strong oxidizing agent. We can also manipulate the environment around the produce to reduce ethylene levels. For instance, storing ripe and unripe produce in separate rooms can help prevent cross-contamination of ethylene. Additionally, using ultraviolet radiation, manipulating the C-O-2 and O2 atmosphere, and applying chemicals like AgNO3, silver thiosulfate, and calcium nitrate can all help control ethylene production..

[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. There are three main types of mechanical damage that can affect fruits and vegetables. Firstly, roller bruising can occur when fruits and vegetables rub against another surface during handling and transportation. This can cause damage to the fruit's surface. Secondly, impact bruising can occur when products drop onto a hard surface during filling and handling of packages. Although this damage may not be visible on the surface of the product, symptoms can appear internally. Finally, compression bruising can occur when fruits and vegetables are squeezed into a smaller space, causing damage to the product..

[Audio] Physiological breakdown occurs when produce is exposed to an undesirable temperature. Freezing injury, chilling injury, heat injury, and physiological problems caused by very low oxygen atmospheres can occur. These injuries can cause defects such as sunburn, bleaching, scalding, uneven ripening, and excessive softening, ultimately leading to loss of texture, structure, and microbial damage..

[Audio] Fungi and bacteria, including yeast and mold, are responsible for the most common symptom of deterioration in fruits and vegetables. These microorganisms take advantage of the succulent nature of the produce, making it easy for them to invade and cause damage. Fungal pathogens like Alternaria, Botrytis, Diplodia, Phomopsis, Rhizopus, Penicillium, and Fusarium, as well as bacterial pathogens like Erwinia and Pseudomonas, are known to cause extensive damage. While microorganisms may consume small amounts of the food, they often damage the produce to the point where it becomes unacceptable due to rotting or other defects. This can result in both loss of quantity and quality. In cases where the disease penetrates deeply, the infected produce may become unusable, while superficial damage can lead to skin blemishes that reduce the value of a commercial crop..