1 week, 5 days ago

Everything is not absolute, so is this sentence. 

No matter what kind of fruit, it has its best storage temperature. For example, the best storage temperature of mango mentioned by the subject is 10 ℃ ~ 13 ℃. In the storage of fruit, if the temperature is higher than the optimal storage temperature, the fruit is prone to deterioration and decay, and lower than the optimal storage temperature, the fruit is vulnerable to cold damage. Chilling injury refers to the damage of fruit caused by low temperature storage above freezing point. Common chilling injury phenomena such as banana and mango are easy to turn black when stored at low temperature, apple and pear are easy to appear water stains when stored at low temperature, kiwi fruit will appear skin browning and lignification when suffering chilling injury. 


 
 chilling injury of kiwifruit. The picture is from Jiangtao Suo et al. Characteristics of learning induced alignment in kiwifruit with different sensitivities to low temperatures [J]. Postharvest biology and technology, 2018, 135: 8-18. 
 
 
 therefore, 
 no matter whether it is tropical fruit or not, as long as the storage temperature is not within the optimal storage temperature range, it is not suitable. 


The main topic mentioned that mango has been stored at 35 ℃ or above for 2 days in the south, which is far beyond the optimal storage temperature. It is not surprising that mango has deteriorated and rotted. After that, the subject put the mango in the refrigerator for a week (generally 0 ~ 4 ℃), although it is not in the best storage temperature range, but the result is "almost intact". Is mango immune to cold damage? 

Of course not. From the experiments done by the subject, we can see that: first, compared with the corruption and deterioration caused by high temperature storage, the chilling injury to the fruit is at most a "slight injury"; second, the chilling injury to the fruit takes a certain time, and the chilling injury effect caused by a few days or even a week or two is not obvious. 


 people who propose that "tropical fruits can't be refrigerated" should consider the result of low temperature and cold damage, but ignore the phenomenon that high temperature storage will accelerate the deterioration. In this respect, the saying "tropical fruits can't be refrigerated" is actually questionable. 


Generally speaking, the best storage temperature of tropical fruits is about 5 ~ 15 ℃, which is higher than the refrigerated temperature. If the room temperature at home is more than 30 degrees, then let the saying "tropical fruits can't be put in the refrigerator" go to hell, and quickly put the fruits in the refrigerator; but if the room temperature at home is more than 10 degrees, it's better to put the fruits in a cool place indoors than in the refrigerator. In addition, 
 immature fruits are more sensitive to low temperature and more vulnerable to cold damage, while the fruits with high maturity have strong cold resistance. 
 therefore, the refrigerator is only suitable for storing mature fruits. If not, it is better to put them outside the refrigerator. 


. The picture is from Susan Lurie et al. Chilling investment in peach and nectarine [J]. Postharvest biology and technology, 2005, 37:195-208. 
 
 
 to solve the main problem. Let's see how to store fruit more scientifically. Before analyzing, let's understand two concepts. 

From the perspective of mature physiological characteristics, fruits can be divided into respiratory climacteric and non respiratory climacteric types. The so-called 
 respiration climacteric fruit 
 refers to the fruit with rapid increase of respiration rate and large amount of ethylene production when the fruit is mature. Their fruits have obvious stages of development and maturity, which often give people the feeling of "suddenly ripe". The common respiratory climacteric fruits are 
 banana, kiwi fruit, mango, persimmon, tomato, apple, pear, peach 
 and so on. 


 non respiratory climacteric fruit 
 refers to fruit that does not have obvious respiratory rate peak and ethylene peak during fruit ripening, and their fruit has no obvious stage in development and ripening, which is basically synchronous, that is, the ripening process is relatively gentle without sudden changes. Common non respiratory climacteric fruits are 
 grapes, oranges, strawberries, cherries 
 and so on. 


. For example, the breath leaping fruit banana, even if it is picked green and hard, not fully mature fruit, but put in the house for a few days or use ethylene to urge, it can also become sweet and delicious mature fruit. But grapes, oranges and other non respiratory climacteric fruits are not the same. If their fruits are picked when they are not mature, that is to say, no matter how much ethylene is used, they can't be ripened. The sour ones are still sour and astringent, and the unsavory ones are still unsavory. They won't ripen and turn sweet after a long time, but will go bad and rot. 


 this means that respiratory climacteric fruits can be picked before they are fully mature, while non respiratory climacteric fruits can only be picked after they are mature on the fruit branches. This tells us that the "life span" of respiratory climacteric fruits will be longer, because we can put immature fruits in the house to let them mature slowly, rather than respiratory climacteric fruits, because they are mature when they are bought back, if not eaten in time, they will soon go bad, so the shelf life is relatively shorter. 

So, before we use storage fruit, we need to think about the type of fruit. 

If it's respiratory climacteric fruits, generally speaking, they are more sensitive to cold (tropical fruits are even worse), no matter whether they are mature when they are bought back, as long as the temperature at home is not too high, it's unnecessary to put them in the refrigerator; if the temperature at home is too high (room temperature in summer), mature fruits can be put in the refrigerator, and immature fruits should not be put in the refrigerator, because For immature fruits are more vulnerable to cold damage, which will not only lead to quality decline, but also make them lose the ability of later ripening, it is suggested that they should be put into the refrigerator after ripening. 

If it is a non respiratory climacteric fruit, generally speaking, they are more tolerant to cold, and they are mature when they are bought back. It is recommended to refrigerate them in the refrigerator in time to reduce the respiration of the fruit, so as to extend the shelf life.

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