Physiological and biochemical characteristics of potato and its fresh-keeping packaging technology

After the potato is harvested, it is still an active organism, and it is still undergoing metabolism during storage, transportation and sales. This is the main factor affecting the storage and freshness of potatoes. After tuber harvest of potato, the dormancy and germination process is divided into three classes. The first class is known as the ripening period of the potato, which is the early stage of storage. The performance of the tuber has not been completely corked, and the water inside the tuber rapidly evaporates. As the respiration is vigorous and the water evaporation is significantly increased, the weight of the tuber is significantly reduced. The temperature is higher, and the water vapor accumulation causes the tuber. Rot. When about 20-35 days of ripening effect, the epidermis is fully corked, and as the evaporation intensity and respiratory intensity are gradually reduced, they go into a dormant state. The second class, known as the potato quiescent period, or deep dormancy, that is, the middle of storage. During this period, the respiration of the tubers slowed down and nutrient consumption was reduced to a minimum. If the temperature is appropriate, the dormancy period of the potato can be maintained for a long period of time, which is generally up to two months or up to more than four months. If you control the temperature, you can promote it to go through the dormancy period as needed, and you can also extend the forced dormancy. The third class is the late dormancy, also known as the budding period, that is late. At this point, the dormancy of the potato is terminated, and the respiration becomes more vigorous; at the same time, due to the accumulation of heat generated by the respiration, the storage temperature is increased, and the potato pieces are promptly germinated. At this time, the weight loss of the potato block is proportional to the degree of sprouting. During this period, if certain low-temperature conditions are maintained and the ventilation of the storage is strengthened, the concentration of O2 and 2 in the package will be kept within a certain range, so that the tuber will be in a state of forced dormancy and delayed sprouting, which is very important for increasing the preservation period of the potato. . Because the germination will cause a large amount of starch contained in the potato block tissue to transform and cause the appearance of wilting, at the same time, the potato germinating parts produce toxic substances, resulting in the loss of sales, processing, and even completely lose the value of food. Common Diseases in Potato During Storage and Physiological Diseases and Infectious Diseases. Physiological diseases are caused by the respiration of the tuber and the disorder of the material metabolism. The most important is potato black disease. Symptoms of the disease are: The dark part of the tuber becomes black gradually and it is covered with black spots. The reason is that the lack of oxygen in the storage environment, resulting in insufficient oxygen penetration into the organization and the accumulation of carbon dioxide gas, because the increase in tyrosinase activity due to potato chips, tyrosinase into melanin and black. When the potato block sprouts, the temperature is high, over-drying, causing damage and heavy pressure in the process of transportation and storage. Infectious diseases are the main diseases in potato storage. There are two kinds of ring rot and dry rot. The former is the potato block infected by ring-infested bacteria, and it has developed and spread. Symptoms are the appearance of recessed heald spots on the outer skin, which then penetrate into the mass of the block. In severe cases, it expands to the inside of the tuber, which is the most likely cause of the disease in a hot and humid storage environment. The optimum temperature for the development of this pathogen is 20-30C. The pathogenic bacteria invade the wound and cannot infect from natural channels. Therefore, to avoid injury during storage, and to maintain a lower temperature, you can reduce the chance of getting infected. The potato is infected with ring rot, and the lumps become pale, giving offensive gas and mucus. Then gradually the whole potato soft rot produced a lot of mucus. The disease is particularly acute when it rains for a long time. Failure to take precautions will eventually lead to complete rot. The latter is known as dry rot, also known as fulminosis. Symptoms are brown stems with white, pink, grayish-blue, and other colors attached to the mold. The tissue darkens and becomes porous, and the interior becomes empty. As a result, the entire tuber fleshy withered. Several important parameters of physiological and biochemical characteristics of potato are described below: (1) Respiration at 0-2 is 1.7-8.4Comg/kg-hour; (2) Temperature coefficient of respiration (representing 10C per temperature rise, breathing The increase in the number of times) is 0.5-10C which is 2.1 and 10-24C which is 2.2. After years of research and practice by experts, it is believed that the fresh-keeping conditions for potatoes are: late-maturing varieties, storage temperature 3-10C, relative humidity 85-90%, and storage period 6-8 months. Early maturing varieties have a storage temperature of 10-13C, a relative humidity of 85-90%, and a storage period of 6-8 months. In addition, the residual oxygen content in the package must not be less than 10%, and it must not allow water vapor to condense on the surface of the potato. At present, potato packaging technology in the world mainly consists of Japan's dehydration and fresh-keeping packaging technology and U.S. ultra-high gas permeable membrane packaging technology, as well as the refrigerated modified atmosphere packaging technology as well as films and radiation. Among them, although there are great advantages in the cold air-conditioning packaging technology, due to the need for cooling equipment and the existence of cold barriers and cytoplasmic ice-blocking obstacles, the promotion of use is limited. The fresh-keeping packaging technology under normal temperature conditions will be developed. Japan's dehydration and fresh-keeping packaging technology uses highly absorbent polymers and activated carbon placed in a bag-like mat to absorb moisture released from the potato's respiration function to regulate moisture, while absorbing respirable ethylene and other gases. , And to absorb the odor of corruption, to prevent condensation; the other is the use of SC film, which also has the function of absorbing ethylene and water vapor, can prevent condensation, but also can adjust the concentration of O2T and CO2 in the package, also has A certain amount of antiseptic effect. The SC film has good transparency and low price, and can prevent the potato from frizz and decay due to moisture evaporation and microbial action. The SC film has good flexibility, is not easily broken, can be used stably for a long time, and has good preservation effect. Ultra-high gas permeability membranes studied in the United States can allow enough oxygen to pass through and avoid anaerobic conditions from occurring, thus achieving optimal atmosphere control and maintaining freshness. The best storage temperature of potato is 1-3C, and the normal temperature is above 18C. Therefore, it is not possible to achieve this requirement by merely using the thermal insulation of corrugated board. Therefore, we can perform some treatment on the insulation of corrugated board. The methods adopted by advanced countries in the world include: reflected radiation from composite vapor deposition film on the outer surface of the carton; use of foamed styrene in the middle of the corrugated cardboard board to increase heat insulation (reduce the number of heat conduction parameters); the other is to use a cooling agent. The coolant is usually a gel liquid of alkane and petroleum hydrazine and sealed in a film bag or blown plastic container. It absorbs heat from the surrounding environment, lowers the temperature, and keeps the fresh potato package at a certain moisture level. Extend the preservation period. And it can be used repeatedly, it can also adjust the amount of cooling agent, made of adjustable fresh-keeping packaging refrigerator. Potatoes are also treated in some ways to improve the effect of fresh potato packaging. Such as: (1) radiation treatment. According to tests conducted by US experts, the application of 60 Cobalt isotopes to potatoes can significantly increase the storage period of potatoes. The safe radiation dose is generally 1-20000 roentgens, and the germination rate is reduced by more than 90% (from 21.4% to 1.05%). The damage and decay were reduced to 1-2% (control was 4.1%); and the preservation temperature could be significantly increased, generally increased by about 10C, and even at room temperature (20C-26C), a good preservation effect could be obtained. The radiation treatment can cause the synthesis of auxin in the growth point of potato tubers to be destroyed and the respiration is weakened. (2) coating treatment. That is, the potato is treated with a solution (coating solution) containing a film former, a preservative, etc. to form a film-like substance on the surface of the potato tuber, which can increase the microbial infection and physiological diseases of the potato and produce good results. . Preservatives commonly used in potato processing include phenomulamine, thiabendazole, and ethyl naphthalate. (3) Strictly select ticks and timely harvest. In order to improve the fresh-keeping packaging effect of potatoes, appropriate harvesting time should be established. For example, autumnal potatoes should be harvested in early November before the onset of early frost, and can not suffer frost. Harvesting should be carried out after the soil is properly dried. The newly harvested potato pieces are soft and tender. They should be put on the ground for 1-2 hours until the surface is slightly dry. The summer sunshine should not be allowed to dry for a long time. In the shade. Before storage, the bad potato pieces such as lesions, insect bites, damage, rain, freezing, and open cuts, as well as pittings, etc., should be strictly excluded. (4) Packaging materials, packaging containers and warehouses. There are a large number of microorganisms that cause potato spoilage. The invasion of microorganisms will affect the preservation and storage effect. Therefore, we must do a good job in packaging and warehouse disinfection, which is an important measure of anti-corrosion damage.


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