catalogue

Fruit preservation method

How to keep all kinds of fruits fresh?

Fruit preservative

How to keep fruits fresh in summer

Fruit preservation method

The methods used by fruit merchants to preserve fruits mainly include carton preservation, microwave preservation, edible fruit preservation, new film preservation, pressure preservation, ceramic preservation bags, microbial preservation, decompression preservation and electronic technology preservation. Ordinary people are familiar with preservation methods.

Twelve methods of fruit 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.

I. Fresh-keeping cartons

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.

Second, 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.

Four, temperature control storage and preservation methods:

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

V. Sources and methods of storage

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.

Six, the 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.

Seven, pressure 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.

Eight, ceramic fresh-keeping bags

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

Nine, 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.

Ten, decompression 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.

XI. Preservation method of 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.

Twelve, 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.

Professional methods for keeping common fruits fresh;

A, citrus preservation method

There are many kinds and varieties of citrus, which are generally storable, but there are also great differences between different kinds and varieties. Generally speaking, lemons are the most storable; Followed by sweet oranges, such as Sichuan Jin orange, true sweet orange, Hunan red sweet orange, Fujian snow orange and so on. Can be kept for about half a year; Third, oranges, such as banana oranges and satsuma oranges; Wide-peel orange has the worst storage tolerance, especially Sichuan red orange. Of course, in every orange population, there are naturally points of tolerance to storage and intolerance to storage. For example, in the wide-peel citrus with poor storability, mandarin oranges and mandarin oranges are storable.

Citrus fruit trees grow in warm and rainy subtropical and tropical areas, so the storage temperature of their fruits should not be too low, which is easy to cause chilling injury. However, respiration increases with the increase of temperature. In order to inhibit respiration and prolong storage life, it is necessary to store at low temperature. According to the test results, the storage temperature of different citrus varieties is obviously different. The suitable storage period of sweet orange is about 2℃ (quoted from Zhang Baichao), generally 3-5℃, 4-6℃ for satsuma, 0/0-/0/2℃ for red orange and 7-9℃ for banana orange, and/0/0-65438 for kloc. Due to the use of preservatives, the storage temperature will also change. The experimental results in some provinces show that citrus fruits can be stored for about half a year under the conditions of high humidity and high concentration of carbon dioxide at storage temperature 10- 15℃. Such a storage temperature can be achieved in many ventilation warehouses, which is conducive to expanding storage.

Second, the fresh-keeping methods of strawberries

Strawberry fruit is bright red and watery, soft and juicy, sweet and sour, and contains rich nutrients such as calcium, phosphorus, iron, vitamin C, etc. Strawberry has high water content and delicate tissue, and is easy to rot and deteriorate due to mechanical damage and microbial infection. At room temperature, the fruit began to change color and taste after storage for 1~3 days, which made it difficult to keep fresh.

Storage method ① Modified atmosphere storage. Cover the sealed strawberry special fruit bowl with a polyethylene film bag with a thickness of 0.04mm and store it at 0 ~ 0.5℃ and relative humidity of 85% ~ 95%. The gas in the bag is 3% oxygen and 6% carbon dioxide. Under these conditions, strawberries can be stored for more than 2 months.

Three, bayberry preservation method

Myrica rubra can be stored at room temperature for a short time without any treatment. As the saying goes, "one day it tastes bad, two days it changes color, and three days it tastes bad." Therefore, it is extremely important to control the appropriate storage conditions. The experiment of Shanghai Fruit Company showed that soaking Myrica rubra fruit in 1000ppm salicylic acid for 2 minutes the next day after harvest could maintain the good quality and flavor of the fruit and reduce the rot rate. According to the experiment, bayberry fruit can be stored for 1-2 weeks at 0-0.5℃ and relative humidity of 85%-90% without deterioration. In addition, frozen storage can keep fresh for about half a year, but generally 1-2 months is appropriate. As far as possible, use small bamboo baskets and baskets as fruit containers, lined with banana leaves and lotus leaves, which can not only play a buffering role, but also keep bayberry moist and fresh.

Fourth, the storage and preservation methods of plums

Modified atmosphere storage: ① Modified atmosphere storage. Plums are sealed in a polyethylene film bag with a thickness of 0.025mm, and can be stored for 70 days under the conditions of air temperature of 0-65438 0℃, carbon dioxide content of 7-8% and oxygen content of 65438 0-3%. ② Modified atmosphere refrigeration in small packages. Prunes harvested at the right time are removed from stems, pests and damaged fruits, packed in polyethylene film bags, each bag is 1- 1.5 kg, sealed and stored at-1℃ for 2-3 months.

Five, apple preservation method

Apples are one of the more storable fruits. However, different varieties have different storage tolerance, among which late-maturing varieties have stronger storage tolerance than early-middle-maturing varieties, and middle-maturing varieties have stronger storage tolerance than early-maturing varieties. Red Fuji, Guoguang and other late-maturing varieties have little change in hardness and quality during storage, and have strong disease resistance and are suitable for long-term storage. Mid-mature varieties such as Red Star, Marshal, Redjade, Jonakin and Beidou are easy to mature after storage, and their quality changes greatly. These varieties have strict storage conditions and generally have a short storage time, but they can also be stored in modified atmosphere until February to March of the following year.

How to keep all kinds of fruits fresh;

Litchi preservation: Litchi is preserved by newspaper.

Divide the newly bought litchi into two parts, one in the bag and the other out. The litchi in the bag is refrigerated in the refrigerator in the ordinary way, and the other part wraps each litchi with paper towels, then puts it in the bag and then refrigerated in the refrigerator. After a week, I took it out and looked at it. Litchi put into the refrigerator in the ordinary way are all dry. Peel it off and see if there is something bad inside. It smells sour. However, the litchi peel wrapped in paper is still fresh, as if it were newly bought. After peeling, litchi meat is still bright and shiny after one week.

This trick also applies to bayberry, strawberry and so on. Larger fruits can also be wrapped in newspapers, which can ensure that there are no rotten fruits in your home.

Watermelon preservation

Cover the surface of watermelon with plastic wrap. In fact, it is not right to keep watermelons fresh like this, because they look very easy in cake cabinet. But in fact, the deli cabinet will absorb water from watermelon skin, so it is useless to cover it with plastic wrap. Therefore, watermelon preservation should be wrapped with plastic wrap, and the skin should be wrapped with plastic wrap together. Then the air is squeezed out;

Papaya preservation

Papaya is also a kind of fruit and can't be kept in the refrigerator. There will be black spots. Although the display cabinet can absorb water, once it is taken out of the refrigerated display cabinet, the temperature difference will produce moisture on the surface of papaya and produce stale black spots. Put it in a cool place. In this way, papaya can be preserved for a long time, and the correct preservation method should be to wrap papaya in newspaper first. Always keep it fresh.

apple

Apples are stored to prevent rot and dryness. In order to prevent rot, we should choose apples with good quality and no rotten spots, and put them at the lowest possible temperature. Of course, they should not be frozen. The way to prevent drying is to pack with airtight plastic bags, tie the bags tightly and put them in cylinders or pipes. Check it every once in a while and take out the bad ones so as not to affect the good ones. If you find that the apple is dry, you can sprinkle some cold water.

Kiwifruit: Kiwifruit should be kept fresh at low temperature.

Rich in nutrients, with the highest vitamin C content, it is "soft for seven days, rotten for ten days, and bad for half a month", which is suitable for storage in the refrigerator at -0.5℃-0℃, and kiwifruit can't be put together with apples and pears, because apples and pears will release ethylene, which will easily accelerate the ripening and decay of kiwifruit.

Bananas: Bananas should not be put in the refrigerator.

Bananas are difficult to store. The key is that the environment humidity is low and it is not suitable for storage in the refrigerator.

If bananas are stored in the environment below 12℃, they will turn black quickly, so it is not advisable to put bananas in the refrigerator. It is recommended to buy bananas slightly raw. If you buy a ripe banana, you can keep it in the shade for a few more days. The correct method of bananas should be to put bananas into fruit fresh-keeping bags. Put it in a cool place. The popular food here reminds everyone not to put bananas in the freezer.

Pear: Pears are wrapped in soft paper.

Pears rot easily. If you keep it, wrap it separately with 2 ~ 3 layers of soft paper, then put it in a carton and put it in the refrigerator. A week later, remove the wrapping paper, put it in a plastic bag, and then put it in the freezer. When the temperature is adjusted to about 0℃, it can generally be stored for one or two months.

Long-term preservation method: dig a deep sewer, keep the bottom of the ditch dry, put pears in the ditch, and keep them in summer without cover. Or when picking the fruit, it will not damage the peel, and it will be hidden with radish to prevent the pears from touching each other and ensure that the pears will not rot for a long time.

tomato

Not suitable for cold storage in refrigerator. When storing, put the half-baked tomatoes into a fresh-keeping bag, tie the bag mouth tightly in the shade, and open the bag mouth once a day for ventilation. If there is steam in the bag, dry it with a clean towel and then tie your mouth tightly. The tomatoes in the bag will gradually mature and can be kept for about a month.

Orange: An orange soaked in garlic water.

Slice 500 grams of garlic, add water to boil, let it cool, soak oranges in water for a few minutes, then take them out and store them. It can keep fresh for 3 months. You can also spread sawdust (about 6 cm thick) on the bottom of the carton, put the orange bottom up and put it in a ventilated place, which can keep fresh for two months.

Oranges and tangerines

After being put in a basin, it can be covered with tidal sand for a long time.

lemon

You can't use a lemon once. Slice, put in ice and freeze to make lemon ice. Put it directly when making drinks. If you want to keep it longer, you can put the lemon slices in a sealed container and soak them in honey. It can be kept in the refrigerator for one month.

persimmon

Choose persimmons that are not fully mature, wrap them in persimmon leaves for several layers, and then hang them with utensils woven with straw for collection, which will not be bad for a long time.

grape

It is very perishable at room temperature, and the suitable storage temperature is-1℃ ~ 0℃. If you want to keep it for a long time, prepare a clean jar, wipe the inner wall with a clean cloth dipped in 70 alcohol, put the grapes into the jar layer by layer, put bamboo curtains between layers, seal it with plastic film after filling, and store it in a cool place for a period of time.

Peach: Select "Exposed White" and refrigerate at 10℃.

It is best for the public to buy peaches that are 70-80% ripe (commonly known as "exposed white", and the skin turns from green to white), which does not feel very hard. When storing, don't stack them, let alone mix them with other fruits. If it's a whole box of peaches, it's best to open the package first and put it in the refrigerator for one night to dissipate heat. Then, put the peaches in fresh-keeping bags, make holes and store them. If conditions permit, the temperature of the refrigerating room can be raised a little, otherwise the pulp will turn black easily and affect the taste.

Peeled fruits should be put into cold boiled water.

After peeling the fruit, if you don't eat it immediately, the air will oxidize the surface of the fruit after a while, making it light brown and very ugly. If the peeled fruit is soaked in cold boiled water, it can not only prevent oxidation and keep bright, but also make the fruit brittle and sweet.

Precautions:

Tropical and subtropical fruits should not be refrigerated.

Mango, pitaya, pineapple, litchi, longan, papaya and rambutan are all popular tropical and subtropical fruits. However, these fruits should not be put in the refrigerator. Because once put in the refrigerator, black spots will appear on its surface in a few days, because most of them are afraid of cold. If the peel is sunken and some dark brown spots appear, it means that the fruit has been frostbitten. Frostbite fruits are not only destroyed in nutrients, but also easy to deteriorate. In a few days, the meat will turn brown and start to rot.

The reason why tropical and subtropical fruits are afraid of low temperature is related to their growing areas and climate. Generally speaking, fruits cultivated in warm areas, especially in summer, are less tolerant to low temperature than fruits cultivated in cold areas and autumn. Therefore, some temperate fruits, such as grapes, apples and pears, can be kept fresh in the refrigerator. Bananas and mangoes will turn black when stored at a temperature of more than ten degrees Celsius. When pineapple is stored at 6℃~ 10℃, not only the peel will change color, but also the pulp will be soaked in water. When litchi, longan and rambutan were stored at 1℃~2℃, the color of the exocarp became darker, and some scald-like spots appeared on the endocarp. This kind of fruit is usually inedible.

In daily life, tropical and subtropical fruits should be stored in a dark place. If it must be stored in the refrigerator, it should be stored in a high-temperature fruit and vegetable jar for no more than two days. In addition, these fruits will accelerate deterioration at room temperature after being taken out of the refrigerator, so they should be eaten as soon as possible. And some tropical fruits, such as bananas with blue colors, which are not yet mature, have worse cold tolerance, so it is best not to put them in the refrigerator. Otherwise, they will not only not mature normally, but also become inedible due to decay.

Fruit preservative

(1) Excessive use of fruit preservatives is harmful to human health.

At present, there are two common methods of fruit preservation in the world. One is an ethylene absorbent, which generally absorbs ethylene with a breathable bag, so that the fruit will not mature further, and it is harmless without medication. The other is waxing. Many fruits produce fruit wax, which can prevent insects, diseases and microorganisms. However, fruit wax is easy to be wiped off during storage and transportation, so edible wax will be used manually.

"This internationally used fruit preservative does not directly act on fruits and is harmless to the human body." The so-called "fruit preservative" does not belong to any of the 23 kinds of additives listed by functional classification in the Standard for the Use of Food Additives. "Fruit preservative is actually a general term for additives such as antioxidants, preservatives and film coating agents. The dosage of these additives is clearly stipulated in the national standards."

Experts said that the amount and residue of additives used for fruit preservation must be controlled within the scope stipulated by the national standard, and excessive use is "harmful and useless". Proper amount of sulfur dioxide has a good preservation effect on litchi, longan and other fruits, but excessive use leads to excessive residues, which not only affects the quality of fruits, but also causes dizziness, nausea, vomiting, diarrhea and even damages the liver and kidney functions.

(B) How to remove preservatives from fruit skin

Nowadays, whether it is in season or not, all kinds of fruits in the supermarket are always dazzling and radiant.

In a word, these are the fruits' preservatives, and it is the preservatives that make these fruits stay young and look old.

In today's healthy and natural diet, do you have any doubts about spraying preservatives on fruits? Now let's find out which preservatives are used in some fruits we often eat. What is the best removal method?

pear

Hupiling, a common preservative for pears, belongs to antioxidant fruit preservative, which is insoluble in water and soluble in ethanol. Hupiling can effectively control the occurrence of black skin disease, a physiological disease of Yali pear during storage.

At present, the common fresh-keeping method is to prepare a certain concentration of liquid medicine with Hupiling and spray it directly on the wrapping paper to make fresh-keeping paper.

Suggested removal method: Because this preservative is sprayed on the preservative paper, it is not directly coated on the surface of the fruit, so it has little effect on the fruit. If you still have concerns, you can peel them off.

apple

The preservative commonly used in apple preservation is thiophanate methyl.

The original drug is colorless crystal, insoluble in water, soluble in organic solvents, and stable to acid and alkali. The drug is a broad-spectrum bactericide of benzimidazole. Commonly used in apples, bananas, oranges, pineapples, cantaloupes, sweet potatoes, etc. Generally, dipping or coating treatment is adopted.

In addition, the preparation has low toxicity to people, livestock, bees and fish, and is safe for crops. It can also be used to control various fungal diseases on fruits and vegetables, such as Sclerotinia sclerotiorum, gray mold and powdery mildew.

In addition, when apples are kept fresh, Hupiling can also be used like pears.

Suggested removal method: Because thiophanate-methyl is insoluble in water, it is best to peel it when eating.

peach

During the storage of peaches, a large number of peaches often rot due to brown rot.

The usual preservation method is antiseptic preservation. Soaking the suspension of benomyl with the mass fraction of 0. 1% at 40℃ for 25 minutes can prevent the peach from rotting.

Suggested removal method: rinse with clear water and rub the peach skin by hand, or peel it.

tomato

O-phenylphenol (alias: apricot, diphenol, sodium o-phenylphenol and 2- hydroxyphenyl) is a common preservative for tomatoes, and its sodium salt has been widely used. O-phenylphenol is pink crystal, slightly smelly, volatile and soluble in many organic solvents.

In particular, o-phenylphenol has a good inhibitory effect on tomato Rhizopus.

In practical application, spray washing, soaking or foaming are generally used.

In addition, there is a preservative, which is often used to keep tomatoes fresh. It is prepared by extracting chitin and its derivatives from crustaceans such as shrimps and crabs, deacetylating them and adding other additives.

When used on tomatoes, the fresh-keeping period can be as long as two months under suitable conditions.

Suggested removal method: rinse with water or peel.

How to keep fruits fresh in summer

In summer, fruits are difficult to store. Here are some tips for keeping fruits fresh in summer.

Maidangling fruit

Nowadays, most fruits are fresh, good in quality and flat in price, so it doesn't cost a lot of money. Unseasonable fruits are not only expensive, but also are likely to be put on the market ahead of time or later due to a large number of pesticides and fertilizers, so try to buy as few fruits as possible.

Nowadays, many fruits can be eaten almost all year round, but there are still some differences in varieties. For example, pineapples with many family members are the most popular from June to August. Among them, the perfume pineapple (Tainong11) blooms from May to June, and the osmanthus pineapple (Tainong18) blooms from April to July, but in August.

In the summer of recent years, many mango varieties have fascinated all beings with their golden color and rich fragrance. Yiwen Mango and Golden Mango, which have the highest yield, are in May-June, while other varieties, such as Kate, have a late production period, about mid-August-September.

There are many fruits in August, including watermelon, cantaloupe, longan, pitaya, peach, Hengshan (high-connected pear) and Century pear. , so that you can grasp the season to buy.

in good health

No matter what kind of fruit, the fruit is full, moderate in size (indicating that the fruit is fully developed), complete in shape, without bumps and spots. , are the basic choice points. The fruit is very heavy, which usually means that it contains a lot of water. It should taste "sweet and juicy". If you pick it up gently, it may have been stored for a while, and most of the nutrients and water in it have been lost.

Look at the color and smell.

Look at the color and smell. Most of the ripe fruits have a strong or light fruit fragrance and bright colors, especially mangoes, pineapples, papayas, apples, cantaloupes and peaches. And more importantly, it is full of color, flavor and good quality.

Other special selection methods, such as grapes with obvious powder and complete pedicels, are usually sweeter in dark color.

Listen to the sound to tell the good from the bad.

When choosing some fruits, you need to practice your fingers and voice recognition first. Just like picking up a watermelon and patting it, if the sound is crisp, it means that the maturity is just right and the water is sufficient. If the watermelon is cut and sold, it should be chosen with thin skin, bright red flesh and no cracks to avoid over-ripening.

If you choose a pineapple, you can also play it with your fingers, and the echo is solid and heavy, which is a good pineapple.

Keep in a cool and ventilated place.

If the fruit you buy is ripe, you can eat it in 1 ~2 days as long as it is placed in a ventilated and cool place, or you can put it in a bamboo basket or fruit bowl. The natural and fresh fruit fragrance can add a bit of charming taste to your home.

Put it in the refrigerator.

Some people are used to throwing all the fruits they have bought into the refrigerator, especially in hot summer, for fear that the fruits will be cooked and stuffy in a few days, and the chilled fruits will taste particularly cold and sweet. Generally speaking, the suitable storage temperature of fruits is between 7℃ and 13℃, and some fruits need lower temperature, such as apples, grapes, peaches, plums and persimmons. The freezer is a good storage place for them. Fruits to be refrigerated in the refrigerator can be packed in plastic bags or paper bags without cleaning first to prevent the moisture of the fruits from evaporating. You can punch a few small holes in the plastic bag to keep it breathable and avoid fruit rot caused by water vapor accumulation.

Some fruits are not suitable for the refrigerator.

Not all the first ripe fruits are suitable for keeping fresh in the refrigerator. Some fruits are naturally "afraid of cold", such as bananas, mangoes and papayas. , is a native product of the tropics. When they are put in the refrigerator, they will be "cold damaged", which will lead to spots on the peel or turn dark brown, destroying the quality and flavor of fruits.