Fruits and vegetables from the seed germination until flowering results are obtained from two aspects: First, the underground part, that is, relying on the developed root system to absorb water and inorganic components from the soil; Second, through the green part, which is mainly the use of light energy and absorption of leaves The inorganic ingredients together synthesize complex organic compounds, a process known as photosynthesis. After the fruits and vegetables are harvested, the supply of nutrients from the roots is completely interrupted, and the remaining parts of the ground cannot continue photosynthesis. However, after fruits and vegetables are harvested, they are still a living organism, and continue to undergo a series of physiological and biochemical changes, so that the unique flavors of fruits and vegetables are further fully revealed. They are more suitable for people's needs in terms of color and flavor. Respiration. This process continues and the fruits and vegetables soften and disintegrate. This is the ageing stage. We understand and understand these changes in fruits and vegetables and their requirements for the external environment, in order to effectively control the regulation and control of environmental conditions, to achieve freshness preservation, and extend the supply period, in order to obtain the best economic benefits. What are the physiological and biochemical changes after fruit and vegetable harvest? 1. Respiration Breeding Fruits and vegetables have an important sign of physiological activity for respiration. Respiration is the most important metabolic process after fruit and vegetable harvest, and it restricts and affects other physiological and biochemical processes. Respiration of fruits and vegetables is a series of enzymes that catalyze the gradual degradation of complex organic matter into simple substances such as carbon dioxide and water, while releasing energy to maintain normal life activities. It can be said that if there is no respiration, there will be no fruit and vegetable life, no fruit and vegetable life, no talk of storage and preservation. We understand that the purpose of fruit and vegetable respiration is to think of ways to take measures to control the respiration process of fruits and vegetables, reduce the consumption of stored nutrients, achieve freshness preservation, and extend the storage period. Factors affecting the respiration of fruits and vegetables include temperature, humidity, environmental gases, mechanical damage, and plant hormones. (1) The relationship between temperature respiration and temperature is very close. Generally speaking, in a certain temperature range, the respiratory intensity is increased by 1 time for every 10°C increase. If the temperature is lowered, the respiratory intensity is greatly reduced. The smaller the respiration intensity of fruits and vegetables, the slower the material consumption and the longer the shelf life. Therefore, the general measure for the storage of fruits and vegetables is to keep the temperature as low as possible and to keep the respiration of fruits and vegetables to a minimum. Lowering the storage temperature of fruits and vegetables can reduce the respiration and prolong the storage time. However, it is not that the lower the temperature, the better. There are certain limits. In general, the minimum temperature requirements for fruits and vegetables grown in tropical and sub-tropical areas or areas of origin are higher, and the lowest temperatures for fruits and vegetables grown in the north are lower. If the temperature is too high or too low, the normal life activities of fruits and vegetables will be affected, and even the normal after-ripening process will be hindered, resulting in physiological injury and death. Therefore, the optimum storage temperature must be selected during storage. The storage temperature should be constant because fluctuations in temperature will promote respiration and increase material consumption. If film packaging is used, dew condensation in the bag will increase, which is not conducive to the storage and preservation of fruits and vegetables. (2) Humidity In general, slight dryness is more moisturizing and inhibits respiration. Different types of fruits and vegetables, the reaction is not the same. For example, citrus fruits have increased respiration in the event of a relatively high relative humidity, resulting in a vigorous life activity of the skin tissue, causing edema disease (floating skin fruit). Therefore, these fruits must be dried slightly before storage. Bananas, on the other hand, do not perform normal postharvest action when their relative humidity is below 80%. (3) Atmosphere The atmospheric composition generally contains 21% oxygen, 78% nitrogen, and carbon dioxide. 03%, and some other trace gases. In the composition of the environmental gases, carbon dioxide and ethylene released from fruits have a significant impact on the respiration of fruits and vegetables. Properly reducing the oxygen concentration in the storage environment and appropriately increasing the carbon dioxide concentration can inhibit the respiration of fruits and vegetables, thereby delaying the ripening and aging process of fruits and vegetables. In addition, lower temperatures and low oxygen, high carbon dioxide will also inhibit the synthesis of ethylene in fruits and vegetables and inhibit the impact of existing ethylene on fruits and vegetables. (4) Mechanical Injury Fruits and vegetables may suffer from extrusion, impact, and puncture during harvesting, grading, packaging, transportation, and storage. In this case, the respiration intensity of fruits and vegetables is increased, which will greatly shorten the storage life and accelerate the ripening and aging of fruits and vegetables. Fruit and vegetables that are mechanically damaged are also susceptible to decay caused by infestation by pathogens. Therefore, avoid mechanical damage to fruits and vegetables during harvesting, grading, packaging, transportation, and storage. This is an important prerequisite for long-term storage of fruits and vegetables. (5) Chemical regulatory substances mainly refer to phytohormone substances, including ethylene, 2.4-D, naphthaleneacetic acid, abscisic acid, cyanogen, chlormequat, B9, and the like. The total effect of phytohormones, auxin and kinetin on fruits and vegetables is to inhibit the respiration and delay ripening. The total effect of ethylene and abscisic acid is to promote breathing and accelerate ripening. Of course, the response of various plant hormones is also very diverse due to the different concentrations and types. 2. Transpiration A series of physiological and biochemical changes in organisms are carried out using water as the medium, ie in the presence of water. Water is constantly changing during the growth and development of fruits and vegetables. On the one hand, the roots of fruits and vegetables continuously absorb water from the soil; on the other hand, the water in the body continuously evaporates from the aboveground parts, especially the leaves. Moisture constantly absorbs the transfer and transpiration, which also promotes the absorption and transfer of nutrients by fruits and vegetables. However, the harvested fruits and vegetables cut off the water source but did not stop the water from transpiration. In this way, fresh fruits and vegetables will therefore lose weight, cause direct losses, and will also cause the fruits and vegetables to lose their luster, shrink, and lose high value. If the relative humidity in the storage environment is not controlled and adjusted, there will also be certain physiological diseases, such as dry citrus, apple splits, dried stems of pears, and certain microbial diseases. The factors affecting the transpiration of fruits and vegetables are: (1) Variety characteristics: The thickness of the skin of different varieties is different. The size of the cuticle, fruit fat, and lenticels on the skin is also different, and thus has different transpiration characteristics. (2) Maturity: Overall, as the maturity of fruits and vegetables increases, the transpiration rate decreases. This is because with the maturity of fruits and vegetables, the growth and development of the peel tissue is gradually improved, and the stratum corneum and wax layer are gradually formed, and the transpiration of fruits and vegetables becomes smaller. However, after some varieties are harvested, there is a tendency for transpiration to progress with the progress of ripening, such as papaya and bananas. (3) Temperature: The transpiration of fruits and vegetables is closely related to the temperature. High temperature promotes transpiration and low temperature inhibits transpiration, which is one of the important reasons for the low temperature in all aspects of storage and transportation. (4) Relative humidity: The relative humidity in the storage environment is the direct cause of the transpiration of fruits and vegetables. The management of humidity in storage is a very important factor. The greater the relative humidity in the storage environment, the less likely the moisture in fruits and vegetables to evaporate. Therefore, the use of water spray, spray and other methods to maintain a high relative humidity in the warehouse can inhibit the transpiration of fruits and vegetables in order to facilitate preservation. (5) Wind speed: The transpiration of water vapor covers the surface of fruits and vegetables to form an evaporation surface, which can reduce the difference in vapor pressure and play a role in inhibiting transpiration. If the wind blows off the water vapor film, it will promote transpiration. (6) Packaging: Packaging has a very significant impact on the evaporation of moisture in fruits and vegetables during storage and transportation. Compared to wooden boxes and baskets, corrugated cartons that are commonly used today have a small amount of fruit evaporated in cartons. If the carton is lined with a plastic film, the evaporation of water can be greatly reduced. Fruit wrapping, plastic film bags, wax coating, and preservatives all have the effect of preventing or reducing evaporation of water.
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