Fruit Ripening

[Audio] The process of fruit ripening involves significant changes that occur within the fruit itself from the time it is picked until it reaches its peak flavor and texture. We will explore these changes in this presentation..

[Audio] By the end of this lecture, you will gain insight into the transformations that take place during the ripening process. We will explore the changes that occur as fruits mature, as well as commercial practices used to facilitate this process. Additionally, we will discuss the ideal conditions necessary for optimal fruit ripening..

[Audio] Commercial practices aim to meet the market demand for ripe fruits and ensure consistent ripening of fruit batches. This becomes crucial during off-seasons when naturally ripened fruits are limited or unavailable, highlighting the importance of artificial ripening techniques in maintaining fruit availability. Throughout both on and off seasons, fruits undergo treatment with various artificial ripening agents to accelerate the ripening process. Controlled atmospheric storage chambers maintain specific conditions, including temperature and humidity, to facilitate the ripening process efficiently..

[Audio] Throughout history, growers have used various methods to speed up the ripening process. Some common techniques include burying fruits in pits, exposing them to smoke, or storing them with other fruits. Farmers would cut or slice figs to accelerate their ripening, while in China, pears were ripened by being exposed to high temperatures in enclosed spaces. These traditional methods ultimately led to the discovery of the role of ethylene gas in the ripening process..

[Audio] As unripe fruit produces ethylene, it induces or turns on genes responsible for producing enzymes. These enzymes then degrade parts of the fruit, leading to an increase in various compounds such as chlorophyll, acids, starches, pectins, and proteins. This degradation ultimately results in the ripening of the fruit..

[Audio] During the process of ripening, several changes occur within the fruit. Starch is converted into sugar, allowing the fruit to attain its full flavor and aroma, thereby becoming ripe and ready for consumption. Additionally, the fruit's color undergoes a notable alteration as a result of the ripening process. Fruits can be categorized based on their ripening behavior, with some exhibiting a climacteric pattern and others displaying a non-climacteric response..

[Audio] As polysaccharides break down, they become more soluble. This process is facilitated by enzymes like pectinesterase, cellulase, and beta galactosidase. These enzymes play a crucial role in degrading the cell walls, leading to significant changes in their structure. The loosening of the xyloglucan-cellulose network allows for increased water uptake, further weakening the cell walls. Major pectin degradation also occurs, resulting in demethylesterification, solubilization, and depolymerization. The loss of galactose and arabinose from the pectin molecules contributes to the weakening of the cell walls, ultimately leading to fruit softening..

[Audio] Starch is converted into sugar by the action of various enzymes such as alpha-amylase, beta-amylase, alpha-1,6-glucosidase, and phosphorylase during fruit ripening. This conversion generates more juice within the fruit, making it sweeter and more palatable. This is indeed one of the key characteristics of fruit ripening..

[Audio] Organic acids such as malic, citric, and quinic decrease during the process of ripening because of increased membrane permeability..

[Audio] As we continue discussing fruit ripening, let's examine how different fruits respond to the process. A list of various fruits, including kiwifruit, papaya, plum, and others, shows distinct reactions. Some fruits, like mebns, experience no significant changes, whereas others, such as imreze, undergo a noticeable increase in certain compounds. Papaya, for example, displays a few changes in its composition, with a slight decrease in water content and a corresponding increase in acid levels. Gh*cose exhibits a more dramatic transformation, with a significant reduction in its original form and the appearance of new compounds. Traces of these changes are also visible in ircrea, where we observe a few alterations in its chemical makeup. Tardo, however, displays little to no change throughout the ripening process. These variations in response to ripening highlight the unique characteristics of each fruit type..

[Audio] During the process of fruit ripening, degradation of chlorophyll pigment occurs, resulting in either anthocyanins or carotenoids being produced. Carotenoids, in turn, have their own biosynthetic pathway, where lycopene serves as the precursor to beta-carotene..

[Audio] As fruits mature, the interaction of various compounds such as sugars, organic acids, phenolics, and volatile compounds, along with esters, aldehydes, and ketones, leads to the formation of new flavors. The specific combination and concentration of these compounds can vary greatly depending on the type of fruit, resulting in the diverse range of flavors experienced when eating different fruits..

[Audio] During the process of ripening, significant changes occur in the development of fruits. These changes involve various biochemical reactions that affect the composition and structure of the fruit. The ripening process can be influenced by factors such as temperature, humidity, and ethylene production. As fruits mature, they undergo physical transformations, including changes in color, texture, and size. Some fruits may also develop new flavors, aromas, and pigments..

[Audio] The primary objective is to meet the market demand for ripe fruits and ensure consistent ripening of fruit batches. This becomes particularly essential during off-seasons when naturally ripened fruits may be limited or unavailable, emphasizing the critical role of artificial ripening techniques in maintaining fruit availability. Throughout both on and off seasons, these fruits undergo treatment with various artificial ripening agents to accelerate the ripening process. The controlled atmospheric storage chambers maintain specific conditions, including temperature and humidity, to facilitate the ripening process efficiently..

[Audio] Calcium carbide is a widely used chemical to speed up the ripening process. However, it's essential to note that it contains toxic substances like arsenic and phosphorus, which can pose serious health risks. When calcium carbide comes into contact with moisture in the air, it produces acetylene gas, acting as a ripening agent. Unfortunately, this process may also impact the nervous system by limiting oxygen supply to the brain..

[Audio] Ethylene is a natural plant hormone that plays a crucial role in the ripening process. As fruits mature, they naturally produce ethylene, which triggers a series of biochemical reactions that ultimately lead to the breakdown of cell walls, the conversion of starches into sugars, and the degradation of chlorophyll, resulting in the characteristic changes we see during ripening. Now, what if we could accelerate this process by exposing unripe fruits to a small amount of ethylene? This is exactly what's done in commercial practices, where a controlled atmosphere is created to mimic the natural ripening process. And the good news is that this method has been widely accepted and regulated by authorities worldwide, including the F-D-A--, which permits its use under specific guidelines. By using artificial ethylene, we can ensure a safer and more efficient way to ripen our fruits, while maintaining their quality and nutritional value..

[Audio] The hormone ethylene initiates the ripening response. In unripe fruit, the physical condition is characterized by being green, hard, and sour with a meaty texture. The chemical cause of this condition is due to the presence of chlorophyll, pectin, and acid. As the ripening process begins, enzymes such as hydrolase, pectinase, kinase, and amylase are produced. These enzymes break down various components of the fruit, leading to changes in its physical condition. Ripe fruit is typically soft, neutral in taste, and has a sweet aroma..

[Audio] Measure to control ripening helps to increase the shelf life of fruits by regulating temperature. The rate of ripening increases with an increase in temperature. Storing fruits at low temperatures immediately after harvest reduces the rate of respiration and ethylene production. However, storing fruits in low temperatures below the optimum level can result in cold injury and spoilage of fruit quality..

[Audio] The natural atmosphere is ideal for the production of ethylene. However, lowering the oxygen content or increasing the carbon dioxide concentration within the storage cabinet slows down ethylene synthesis. Moreover, decreasing the oxygen level below 5% and increasing the carbon dioxide concentration between 3-10% delays ripening by inhibiting ethylene production, thereby extending the shelf life of fruits..

[Audio] Potassium permanganate is a good ethylene absorbent, which means it can effectively remove ethylene from its surroundings. One way to utilize this property is by using potassium permanganate-coated newspaper as a packaging material. When placed at the bottom of a container holding fruits, it can delay the ripening process. By absorbing ethylene, the coated newspaper helps to reduce the concentration of this gas around the fruits, thereby slowing down the ripening process..

[Audio] Ensuring top-quality products is one advantage of delaying the ripening process. By allowing fruits to mature naturally, consumers receive better value for their money. Additionally, this approach opens up new market opportunities and reduces post-harvest losses..

[Audio] Fruits undergo a complex process called ripening, which involves numerous physiological, biochemical, and organoleptic changes. This process ultimately leads to the development of a soft, edible, and ripe fruit with desirable quality attributes. During ripening, the cell walls of fruits undergo significant modifications, primarily affecting starch, pectin, cellulose, and hemicellulose, which are the main types of polysaccharides involved. Additionally, various biochemical changes take place, including chlorophyll degradation, the synthesis of anthocyanins and carotenoids, decreases in acidity, and the development of volatile compounds. Ethylene, a plant hormone, regulates fruit ripening..