In order to produce fruit juice drinks with good quality and fresh taste, we must do a good job in the storage of raw fruits before fruit processing. We will explain the storage of fruits in detail from the following aspects:
(1) The storage tolerance of variety fruits is the internal factor determining the storage of fruits. Not only different kinds of fruits have different storage tolerance, but also the storage tolerance of the same kind of fruits varies from variety to variety. Berries have poor storage resistance because of their tender, juicy and nutritious fruits. Among the kernel fruits, the apple pericarp is tough, with obvious keratinized pericarp in front, so it is relatively resistant to storage; Peach and apricot are relatively poor in storage resistance because they mature in summer. Citrus sweet orange has good storage resistance, while wide peel orange is easy to rot due to the infection of Penicillium and chloromycetes. Among the different varieties of the same kind of fruit, the fruit of late maturing varieties has a long growth and development period, the temperature in the mature period gradually decreases, the fruit grows dense and solid, and has a certain hardness and elastic skin tissue, which is conducive to the fruit to resist mild impact, corrosion and microbial infection. The enzyme activity in the fruit of late maturing varieties is often synthesis greater than hydrolysis, It has a large accumulation of nutrients, a strong oxidation system, good adaptability to low temperature, can ensure normal metabolism during storage, and has a strong ability to resist microbial infection. When the fruit is mechanically damaged or infected by microorganisms, the respiration of late maturing fruit species is sharply strengthened, which is conducive to positive self-defense reaction. Early maturing varieties grow and mature at high temperature. After maturity, if they are stored at high temperature, the nutrition consumption is too fast, and bacteria are easy to invade and cause decay; If stored at low temperature, it is prone to physiological disorders, wrinkled skin and hair. The activity of oxidation system and anaerobic system of early maturing varieties is weak, and anaerobic respiration is relatively significant, which is easy to cause the accumulation of some harmful metabolites. Early vegetable varieties grow rapidly, and their tissues are relatively loose and soft. When they are affected by mechanical damage or microbial infection, their aerobic respiration changes very little, or even inhibited, and their self-defense response is weak. Therefore, late maturing varieties with storage resistance are generally selected for fruit processing.
(2) Fruit maturity in the process of fruit growth, development, maturity and senescence, once the fruit reaches the edible maturity stage, the respiration will soon enter the decline stage. The fruit will senescence, its storage resistance will decline and its quality will deteriorate. Therefore, the fruits used for processing and storage should be picked at the harvest and maturity period, so that the fruits are more resistant to storage. The fruit maturity is low, the development of its surface protective tissue is not perfect, the water holding capacity is poor, and the fruit is easy to lose water. At the same time, the fruit has strong vitality, vigorous respiration and metabolism, consumes more nutrients and has more weight loss. Therefore, the fruit is picked prematurely. The fruit not only does not have the inherent flavor of the variety, but also has more mildew during storage and transportation. On the contrary, when harvested too late (except citrus), many climacteric fruits mature, fall off and decay quickly on fruit trees. This kind of fruit has no value of processing and storage.
(3) Low temperature with proper storage temperature is an important means to ensure safe storage. On the premise of not disturbing and destroying the normal metabolic function of the slow surface of the fruit, the lower the temperature, the longer the storage life. The fruits to be stored in the cold storage shall be stored in the warehouse in time, and the warehouse temperature shall be adjusted to the appropriate low temperature range as soon as possible, so as to maintain the storage resistance of the fruits as much as possible. The storage temperature is adjusted and controlled according to the physiological characteristics of various fruits. Some fruits require a small temperature change during storage, because the temperature fluctuation can stimulate the hydrolase activity in the fruit, promote respiration and increase consumption. Under the storage environment of 0 ℃, the enzyme activity is inhibited and the hydrolysis becomes slow accordingly. Suitable low temperature can inhibit the water evaporation of fruits and the harm of microorganisms. When the storage temperature is low, for example, the moisture content in the air remains unchanged. With the decrease of temperature, the saturated water pressure decreases, the relative humidity increases, and the humidity saturation difference also decreases. Therefore, the evaporation moisture of the fruit to the surrounding air decreases. At the same time, many harmful bacteria and fungi grow slowly at low temperature and will not harm the fruits that maintain normal metabolic function.
(4) Mechanical damage. For fruits with stabbing, falling, bumping, crushing, insect injury and other injuries, the respiration will be greatly enhanced, and the protective layer of the fruit and the tissue structure at the damage will be damaged, which will lead to the invasion of microorganisms, strengthen the water evaporation of the fruit and increase the production of ethylene. Obviously, this is extremely unfavorable to storage. Moreover, stabbing, falling, bumping and squeezing fruits are often not easy to be found, resulting in hidden dangers. After microbial infection and decay, it will spread to other fruits. Therefore, in order to improve the quality of processed and stored fruits, appropriate measures should be taken before harvest. After harvest, from sorting to container, packaging, transportation and storage, attention should be paid to ensure that the fruits are not mechanically damaged and avoid the damage of appearance and internal quality caused by various injuries.
(5) The dormant spores of microorganisms and the hyphae and spores of fungi are very fine and widely exist in air, water, soil, containers and tools. Some of these microorganisms are specific, parasitic on one or several fruits, while others are facultative or saprophytic. Once they adhere to the fruit, they reproduce quickly. Although the fruit has the ability of self-defense, it is limited. When there are many microorganisms, the fruit will rot and deteriorate. Therefore, chemical disinfection and sterilization should be carried out for storage places, containers and tools to control the harmful effects of microorganisms to a low level. At the same time, fruit soaking (washing) with fruit chemicals or wrapping fruits with paper can reduce the chance of microbial infection. It is not suitable to use one for chemical agents. Because microorganisms will adapt quickly and gradually produce drug resistance, which will reduce the storage effect. Rotten fruit should be specially treated. It's best to bury it deeply and burn it. Don't litter it, otherwise the fruit diseases caused by microorganisms will spread quickly.