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How to keep fruits fresh?
1. Fruits to be refrigerated:

Grapes, apples, lotus seeds, guava, strawberries, cherries, pears and oranges. However, the temperature and humidity in the refrigerator are low, and the fruit is easy to lose water. Many people may have experienced it. Some fruits will wrinkle, dry and shrink if they are put into the refrigerator unpacked or refrigerated for too long.

Fruits that are easy to lose water in cold storage environment include pears, lotus plums, guava, cherries, longan and so on.

Avoiding water loss is the key to cold storage. This kind of fruit is afraid of losing water, but it also needs breathing. So you can wrap it in paper and put it in a plastic bag. Plastic bags prevent refrigerators from absorbing water from fruits, while paper helps to absorb water and prevent water from condensing to produce bacteria and molds. Remember that you don't have to prick the mouth of the plastic bag as long as it is slightly knotted. Keep it ventilated and don't suffocate the fruit.

2. Fruits stored at room temperature for several days before refrigeration:

Peach, sweet peach, banana, kiwi fruit, carambola, Sakyamuni, sweet persimmon, avocado, etc. Take temperature-sensitive fruits such as peaches, sweet peaches and plums as examples. The ideal storage temperature before ripening is 10 ~ 25.6℃. In summer, it should be ripened indoors in the shade, and it can be refrigerated after softening slightly.

Because the dangerous temperature of peaches and plums is 1.7 ~ 10℃, and the refrigeration temperature of refrigerator is 4℃, which is within the dangerous temperature range. If peaches and plums are refrigerated before they are fully ripe, they will destroy the fruit tissue and lose water.

When the temperature exceeds 29℃ in summer, peaches and plums will start to ripen irregularly, which will also cause harm.

Post-ripening refrigeration is the key to preservation. After-ripening fruits need to be cooked in a cool place indoors, and they still need to be refrigerated after ripening, otherwise the fruits will still be over-ripe and broken; Indoor temperature can be used to decide whether to refrigerate in autumn and winter.

How to judge whether the fruit is ripe?

The maturity of peach, plum, kiwi fruit, Sakyamuni, sweet persimmon and other fruits can be distinguished by hardness. Banana, carambola, avocado and other fruits are judged by their colors, which usually turn from green to yellow before they are mature, while avocado will turn black.

Take the delicate and difficult-to-manage ripe peach as an example. Li Jinyi, who has been doing fruit business for 30 years, shared a small step of skimming fat. After buying it, it needs to be kept at room temperature for about 2 days, and it can be put into the refrigerator for refrigeration if it softens slightly. Before eating, it will be thawed for 2-3 hours, with moderate hardness. However, peaches are also fruits that are afraid of losing moisture in refrigeration. They also need to layer paper and plastic bags to prevent the refrigerator from absorbing water.

In addition, tropical fruits, such as pineapple, banana, mango, papaya and so on. , are also afraid of cold, easy to catch a cold. If they need to be refrigerated after maturity, it is recommended to eat them as soon as possible within two days.

3. Fruits that cannot be put together with other fruits and vegetables:

Apple, Sakyamuni, pear, papaya, banana, etc. This fruit releases a gas called "ethylene" during ripening. Ethylene will accelerate the ripening and aging of fruits. If common vegetables and fruits are put together with this kind of fruit, it is easy to age and rot early.

In the fruit pile, if a fruit is bad, it should be picked out immediately, because the bad fruit will also start to release ethylene, which will make other fruits go bad one by one.

Separate packaging and placement are the key to preservation. This kind of fruit needs to be separated whether it is refrigerated or stored at room temperature. If it is refrigerated, it is recommended to put it in a plastic bag and make a summary at the mouth to avoid the released ethylene affecting the quality of other fruits in the refrigerator.

If the fruit is well preserved, you must first buy it wisely.

If you don't want to worry about saving fruit, the best way is to buy it in moderation, which can be small and varied, and eat it within one week. Of course, we should also choose the fruits that are abundant in the season, because they are the freshest and the quantity is much cheaper.

Big fruits sell well and are expensive. If you eat it yourself, it is recommended to buy small fruits, which are large in quantity and can be eaten several times. If it is post-ripened fruit, you can choose one that can be eaten on the first ripe day, and the other that is slightly greener can be left at home for 1 ~ 2 days.

Twelve methods of fruit storage and preservation

Fruit is fresh food, and it will rot easily after harvest. In order to prolong the shelf life, researchers from all over the world have invented a variety of new preservation technologies, and now they have introduced 10.

Preservation carton

This is a new type of carton developed by Japan Food Distribution System Association in recent years. The researchers used a kind of "rectorite" (a silicate rock) as an additive for paper pulp. Because this kind of stone powder has a unique good adsorption effect on various gases, and its price is cheap, it does not need low-temperature and high-cost equipment, especially it has a long-term preservation effect, and the weight of fresh fruit will not be reduced, so merchants love to use it, which is more suitable for long-distance storage and transportation.

Microwave preservation

This is a fresh-keeping method for a Dutch company to sterilize fruits at low temperature. After being heated to 72℃ by microwave for a short time (120s) and then put into the market at 0~4℃, the processed food can be preserved for 42~45 days without deterioration. It is very suitable for supplying "seasonal fruits" in the off-season and is favored by people.

Edible fruit preservative

Edible fruit and vegetable preservative is a translucent emulsion made of sugar, starch, fatty acid, polyester, etc., which covers the surface of fruits to form a sealing film to prevent oxygen from entering the fruits and vegetables, prolong the ripening process and play a fresh-keeping role. The shelf life of fruits can be extended to more than 200 days. The most valuable thing is that the edible fruit and vegetable preservative can also be eaten with fruits and vegetables.

Temperature control storage method

Temperature controlled storage can be subdivided into simple storage, cold storage and freezing point control. Burying, piling, cellar storage and ventilation storage are all simple storage methods. The fresh-keeping utilization rate of refrigerated fruit is lower than the freezing point of fruit tissue, which reduces the respiratory metabolism of fruit, the incidence of pathogenic bacteria and the decay rate of fruit, and realizes the storage and fresh-keeping of fruit. It is the main form of modern fruit storage. However, in the preservation of frozen fruits, attention should be paid to controlling the temperature according to the different habits of fruits to prevent chilling injury and freezing and avoid the loss of edible value of fruits. At present, the technology of controlling freezing point storage and preservation has been popularized in Japan, which can keep fruits fresh at freezing point humidity. 4, the source of storage and preservation method

Storage and preservation method of origin

The preservation method of origin storage is a traditional fruit preservation method in China. The cellars in Sichuan, caves in Hubei and caves in the Loess Plateau are all good treasures. The fruit preservation method in producing area has the advantages of low investment, simple management, local storage and low energy consumption, supplemented by mechanical refrigeration, room temperature two-phase dynamic air conditioning and other technologies, and has been widely used in daily life.

New film preservation

This is a disposable moisture-absorbing and fresh-keeping plastic packaging film developed in Japan. It consists of two translucent nylon membranes with strong water permeability, and the natural paste and syrup with high osmotic pressure are filled between the membranes, which can slowly absorb the water oozing from the surface of fruits and meat and achieve the effect of preservation.

Pressurized preservation

It is a method of making food by pressure, which was successfully developed by the Institute of Food Science of Kyoto University in Japan. After pressure sterilization, the fresh-keeping time of fruits can be prolonged and the fresh taste can be improved. But acid can't work under pressure, so it is ideal to keep the fruit in the best condition.

Ceramic fresh-keeping bag

This is a kind of fruit fresh-keeping bag with far infrared effect, which was developed by a Japanese company. The inside of the bag is mainly coated with a very thin layer of ceramic material, so the infrared ray released by the ceramic can have a strong "resonance" movement with the moisture contained in the fruit, thus promoting the fresh-keeping effect of the fruit.

Microbial preservation method

Ethylene can promote the aging and ripening of fruits, so it is necessary to remove ethylene in order to keep fruits fresh. Scientists isolated a kind of "NH- 10 strain" through screening and research. The strain can be made into "ethylene remover NH-T" to remove ethylene, which can prevent grapes from browning, loosening and falling off during storage, prevent tomatoes and peppers from losing water, changing color and softening, and has obvious fresh-keeping effect.

Vacuum preservation method

It is a new fruit storage method with good fresh-keeping effect, convenient management, simple operation and low cost. At present, some countries such as Britain, America, Germany and France have developed low-pressure containers with standard specifications, which are widely used in long-distance transportation of fruits.

Method for preserve hydrocarbon mixture

This is a "natural edible preservative" developed by a British biotechnology company, which can extend the shelf life of pears, grapes and other fruits by 1 times. It uses a complex hydrocarbon mixture, which is dissolved in water to form a solution, and then the fruit to be preserved is soaked in the solution, so that the surface of the fruit is evenly coated with a layer of liquid agent. This greatly reduces the absorption of oxygen, and almost all the CO2 produced by fruits is discharged. Therefore, the role of preservatives is similar to that of "anesthetics" acting on fruits to make them dormant.

Electronic technology preservation method

It uses negative oxygen ions and ozone generated by high-voltage negative electrostatic field to achieve its goal. Negative oxygen ions can inactivate enzymes that metabolize fruits, thus reducing the respiratory intensity of fruits and weakening the survival of ethylene, a fruit ripening agent. Ozone is a strong oxidant and a good disinfectant, which can not only kill and eliminate microorganisms and toxins secreted by fruits, but also inhibit and delay the hydrolysis of organic substances in fruits, thus prolonging the storage period of fruits.