At what temperature is it best to store food in the refrigerator. What factors other than temperature affect the shelf life of vegetables? How to store vegetables so that they stay fresh for a long time
Fresh vegetables require special storage necessary for the long-term preservation of their attractive appearance, excellent taste and maximum natural benefits.
In natural vegetables, the biochemical processes that determine their nutritional properties do not stop for a minute.
Moreover, by understanding how the preservation of vegetables is related to environmental factors, it is possible to achieve long-term maintenance of the quality of such products.
With these fruit and vegetable preservation tips, it was more clear to you which ones should be room temperature and which ones should be refrigerated. You know that feeling of complete satisfaction when you wake up hungry, you go to the kitchen, you open your refrigerator and you will find it full of food. But you also know another sensation that you hate with all your might: finding yourself with spoiled food at yogurt. In order for your refrigerator to have only joys, you just need to maintain order inside it.
A very simple action that you will need to remember every time you make a purchase and it will help you better preserve your food so that your refrigerator is in good condition and even reduces energy consumption. Packaged products. Something very typical among young people in the house is opening a cold cut bag to make a snack sandwich and putting it back in the fridge. Then, when we want to use it again, the ham is dry and ready to be thrown. It is important to always leave food wrapped or covered with a transparent film in the refrigerator.
What happens to vegetables during storage?
Even after harvesting vegetables from the garden, various physical and biochemical processes take place in them, which significantly affect the degree of their preservation.
The nature of these processes is determined by the following factors:
- natural properties of vegetables;
- condition of the skin of the fetus;
- maturity level;
- storage method, etc.
Harvested vegetables undergo processes similar to those that occur in growing fruits. However, there is an important difference here: the growth of vegetables involves not only the decomposition of organic components, but also their active synthesis, while the stored fruits only contribute to the breakdown of these substances, accompanied by the release of energy required for cellular functioning.
This will prevent the food from dehydrating or losing its nutritional value, and we will also avoid mixing odors. Hot food or drinks A very common mistake when finishing a meal is to store food in the refrigerator while it is still hot. Something that manifests itself in the light of light, because as the temperature inside the refrigerator increases, we force the appliance to use more energy to restore the programmed temperature. Another reason why we should release food is to avoid direct contact between the food and the back of the appliance, otherwise free air circulation will be affected.
Processes that take place in vegetables and are of a physical nature
In vegetables in the refrigerator, the processes do not stop:
- evaporation of moisture;
- heat dissipation;
- temperature changes.
The rate of evaporation of the liquid depends on the level of damage to vegetables, atmospheric humidity, temperature, storage method, as well as the activity of aerobic respiration, which affects the generation of moisture.
Fruits and vegetables We want to eat well and eat fresh food. I wish we had a whole garden in our homes to pick our own fruits and vegetables every day, but for those who don't have much space, there is. The box that creates optimal conditions storage of fruits and vegetables, maintains freshness twice, thanks to the control of the degree of humidity.
Meat, sausages and fish And meat and fish? Where do you usually store them? Freezing food If you buy frozen food from the supermarket, it's best to take it home in an insulated bag. We will place the fresh food in the top compartment as it will freeze faster there, and we will try to distribute it so that the frozen food does not come into contact with the fresh food we have just frozen. It is also important to check the expiration date of food.
At the initial and final storage period, water from fruits evaporates quickly (this process is even more accelerated at low humidity and high air temperature). Although practical experience shows that vegetables in such conditions wither.
How should vegetables be stored to keep them fresh for a long time?
The temperature of their storage should not be too low, otherwise the fruits will simply freeze.
This department that gives you so much asks you very little: the door is always well closed. Otherwise, we will see how a strong accumulation of frost occurs, as well as a high consumption of electricity. Another factor to keep in mind is service, and especially when you are planning to go on vacation.
If you ask how we know so much about refrigerators, it's because in Balai. Because something similar happened to you, right? The function of a refrigerator is to better preserve certain foods and prevent them from decomposing at room temperature. However, not all sandwiches need to be stored in this appliance, as some get worse even more quickly with a cold.
- eggplant - 7-10 ° C;
- green peas - -0.5-0 ° C;
- lettuce, spinach, onion - 2 ° C;
- zucchini - 3–4 ° C;
- white cabbage - 1.5-1 ° C;
- potatoes - 3-4 ° C;
- onions - -2 ° C;
- carrots - 1°C;
- sweet pepper - 3-4 ° C;
- radish - 3°C;
- beets - 2 ° C;
- tomatoes - 4°C.
What happens when vegetables freeze?
At first, their temperature drops below the freezing level, without being accompanied by the formation of ice crystals. Fruit tissues are supercooled. The water contained in the cells of vegetables does not freeze. When it turns into ice, latent heat is released, and the temperature in the tissues immediately rises to -0.8–1.8 ° C, stays at this value for a short time and decreases again. This maximum point reached due to supercooling is called the freezing point.
Onions should be kept in a cool, dry and well ventilated area. According to the National Bulb Association of the United States, this vegetable should be stored without peeling and requires exposure to air for optimal shelf life, so it should not be placed in plastic bags. The only exception is when the onions are already peeled and cut, they should be stored in a closed container in the refrigerator.
The Canadian Product Marketing Association states that squash should be in a well ventilated, dry, dark and cool area. She suggests leaving whole melons and watermelons at room temperature to retain these antioxidants. When they are cut, they need to be covered and put in the refrigerator.
It is not necessary to bring vegetables to freezing, because in this case their structure is destroyed. Eating frozen fruits is undesirable.
What factors other than temperature affect the shelf life of vegetables?
Among these factors it is worth mentioning:
- indicators of air humidity;
- the degree of its ventilation and circulation;
- illumination.
Air humidity
Air humidity significantly affects the degree of preservation of fruits. The high water content of vegetables suggests that the most optimal air humidity should be as high as 100%. However, this increases the risk of microbial growth, so the recommended humidity for storing vegetables should be 85-90%.
Garlic should be stored in a dark and dry place, as the refrigerator runs the risk of starting to sprout. They should be stored in a dark, cool and dry place, according to Alberta potato growers in Canada. They recommend placing them in a well-ventilated cardboard box. If you get your potatoes wet before storing, the moisture can cause the fungus.
Damascus, bananas, kiwi, plums, peaches and mangoes
The Ontario Beekeepers Association states that honey should be stored in a tightly closed container at room temperature in a dry place. In addition, cooling can cause crystallization. Ontario Greenhouse growers claim cold air can turn tomato pulp into mush. It's best to have them at room temperature, and in case of a mistake, putting them in the refrigerator, leaving them a day before eating, that some of the flavors are restored. The Canadian Food Marketing Association states that these fruits should be stored at room temperature so that they retain their nutrients better.
However, a number of vegetables (onions and garlic) are stored at reduced air humidity (75–80%).
Ventilation and air circulation
Ventilation is a process in which air enters the refrigerator compartment from the outside, and circulation is the internal movement of air. Ventilation is needed to maintain a certain temperature and humidity indicators.
Coffee should be stored in an airtight container and in a cool, dry and dark place to preserve its flavor and freshness. According to Mikel López Iturriaga, low temperatures negate the enzymes that allow them to ripen. Then other enzymes become stronger: some cause cellular damage.
Chocolate is another common victim of Novism. If it does not contain milk filling or it is very hot, there is no need to put it in the refrigerator. If you put chocolate or an open candy bar in, you'll see some sort of whitish layer appear: a sign that its texture and flavor have been altered, Mikel says.
Types of air ventilation:
Natural ventilation - operates on the principle of heat exchange. The air in the tissues of vegetables heats up due to heat release, which accompanies the respiration of fruits. Then it expands, becomes lighter and, together with water vapor, rises up, where it exits through the exhaust pipes. And cold air, on the contrary, enters these pipes. Ventilation is considered efficient if the temperature difference between the incoming and outgoing air is significant.
A Spanish columnist says that a very common mistake is to put bread in the refrigerator. Contrary to what it seems, they grow faster than in a basket of bread on the kitchen table. If you want to keep for more than a couple of days, it's best to freeze slices or small pieces and thaw in a toaster or at room temperature.
If you find this note interesting, feel free to share it. Your contacts will be grateful. Many times we think that storing most food in the refrigerator is best to avoid the appearance of microorganisms that damage food and cannot be consumed, but this is not always the case.
Mechanical (forced) - carried out by means of electric fans and creates the opportunity to regulate the temperature and humidity of the air, which extends the shelf life of vegetables.
Active ventilation - involves periodically blowing the fruits with a vertical air flow.
What happens is that the cold can speed up the decomposition process of some of them and cause them to lose their original flavor. The main factors influencing the preservation time are the salt and sugar contained in each food, as well as the amount of water inside, acidity, packaging and special procedures such as, for example, the smoking process.
Food that is not suitable for refrigeration
What happens with potatoes and sweet potatoes is that the cold of the refrigerator turns the starch into sugar, so it changes the flavor and texture of the starch, leaving these foods more fluffy and sweet. In turn, this can lead to an increase in a chemical called acrylamide, which is not good if the potatoes are fried or baked at high temperatures. Therefore, it is better to store them in paper or mesh bags in a dry and dark place, such as a pantry. It is also important to keep them separate from onions.
Recirculation in a refrigeration unit can be complete or partial. With full recirculation, ventilation is carried out only by the air of the refrigerator, and with partial recirculation, thanks to the supply of outside air. Can also be applied special heating air to optimum levels.
illumination
Under the influence of light, the processes of enzyme formation are activated - potatoes, for example, begin to germinate. To prevent this from happening, it must be placed in darkness.
Cold air reduces its flavor and texture because it slows down the ripening process of the tomato, which is what gives it its flavor. In turn, the cold causes the membranes to break inside the walls, giving it a floury texture. It is then recommended to keep them in a bowl or basket or cart and if they become mature cook them or make a tomato sauce.
Mostly subtropical fruits such as banana or banana, mango, pineapple and papaya are very susceptible to cold. Low temperatures weaken their tissues, as well as annihilate the enzymes that allow them to ripen, causing damage to their surface, darkening, watering, and loss of flavor. The best way to avoid this is to keep them in a warm place in the kitchen.
The purpose of cold storage is to ensure the invariance of the properties of products for a technologically specified time. In refrigeration technology, the storage process is considered as the main technological process. All previous methods of refrigeration processing of products are intended only to prepare the product for subsequent short-term or long-term refrigeration storage.
Keeping it in the refrigerator delays its maturation. If you need them to ripen, it is recommended to store it at room temperature. Once it's ripe, and if you're still not hungry, it's best to leave it in the fridge. 
It is advisable to store the oil in a cool and light place to avoid flavor changes, as the cold condenses it and solidifies it, taking on the consistency of an oil.
For short term storage the product is generally stored at near cryoscopic temperature.
Long term cold storage provided by pre-freezing.
In the refrigerators of commercial enterprises, the frozen product is stored for a relatively short time. Under these conditions allowable temperature storage temperature is -18...-12 °C, the recommended temperature is -24 °C or lower. In refrigerators of trading bases and warehouses, the lower limit of food storage is not limited. Optimum temperature storage, at which there is practically no change in the quality of products during the established shelf life, is -35 ° C.
Although cold won't damage bandages, they can be stored outside of the refrigerator when they are vinegar and oil based, such as vinegar, mustard, hot sauces, and ketchup. 
It is very important that this food be well coated and at ambient temperature as it crystallizes and thickens more easily in the refrigerator.
The duration of refrigerated storage depends on the type of product, its condition at the time of storage. For perishable products, the maximum shelf life in refrigerators of trade and public catering establishments usually does not exceed 7-10 days. (for example, mature tomatoes) and 6-8 months. for more resistant foods (e.g. onions, smoked meats).
Recommendations for the refrigerated storage of perishable products in refrigerators of trade and public catering enterprises and the recommended modes and duration of refrigerated storage are reflected in the regulatory and technical documentation .
Forced air circulation, carried out by fans, is necessary only in the storage rooms of chilled products to equalize the temperature and humidity of the air throughout the volume of the chamber, remove the moisture released by the products, gaseous substances and heat (during the “breathing” of eggs, fruits and vegetables). The speed of air movement in the chamber is 0.1...0.2 m/s (change 4...8 volumes per hour).
Forced air circulation in the storage room for frozen products is harmful, as it increases the shrinkage of the products. In these chambers, a weak natural circulation (at a speed of 0.03 ... 0.08 m / s) is quite sufficient.
For most products, it is enough to introduce up to 3 volumes of fresh air per day into the chamber (with pre-cooling and dehumidification in the air cooler).
For creating good conditions in the cells instead artificial ventilation purify the air from dust and microorganisms by using filters made of activated carbon. UV lamps are used against mold. To eliminate odors, the air is ozonated (when storing low-fat products).
3.2 Herbal products
The temperature and humidity conditions for storing fruits and vegetables are limited by the temperature range of -3...+5 °C and relative humidity of 85-95%. However, this limitation is purely qualitative, not reflecting the individual storage conditions of fruits and vegetables. For example, most varieties of apples of European origin should be stored at 4–5 °C, since lower temperatures are harmful to them. American varieties of apples store best at 0°C.
The well-known variety "Jonathan" at 0 ° C falls ill with internal browning of the pulp; "Orange coke" lasts up to 4 months. at +4 °C, "mackintosh" - at +5 °C, and for the storage of apples of the "Richard" variety, a stable temperature of 0 °C is required.
A similar picture is observed during storage of pears. It is recommended to store pears of the Williams variety by the method of stepwise cooling, i.e. gradual decrease in temperature from 0 to -1.5 °C. Thus, the storage regime is individual for each product and, most importantly, it depends on the stability of the temperature in the chamber, excluding its fluctuations of more than ±5 °C and relative air humidity of ±5%.
Refrigeration is widespread fruit storage in a controlled atmosphere. The method has an advantage, since it allows, by maintaining a certain gas composition of the medium, to regulate the physiological and biochemical processes occurring in the fruits and thereby prevent premature overripening of the fruits and the occurrence of a number of physiological changes.
The method is based on the storage of fruits in the air with the individual composition of the gaseous medium, mainly CO 2 , O 2 , N 2 , individual for each type of product. Content carbon dioxide take equal to 10-15% concentration, oxygen - no more than 10%.
When storing fruits in a controlled atmosphere, the most noticeable results were obtained when storing apples and pears. Depending on the variety and composition of the gas environment, apples are stored for up to 270-300 days,
pears - 150-200 days. with preservation of appearance and meet the requirements of the quality standard.
Grapes are less stable during refrigerated storage in a gaseous environment. Satisfactory storage (up to 9 months) of grapes is achieved when stored in an SO 2 environment.
Compared with traditional methods, no differences were found in the storage of lemons in a controlled gas environment.
Oranges and tangerines in a controlled gas environment retain commercial qualities for no more than 25-30 days.
3.3 Animal products
Air temperature in the storage room frozen meat should be no higher than -18 ° C at a relative humidity of 95-98%. The recommended temperature is -24°C and below. The speed of air movement is 0.2-0.3 m / s.
The variety of products determines the differences in the recommendations for their refrigerated storage. However, from the variety of parameters that determine storage conditions, in practice, only temperature, relative humidity and air velocity are distinguished. Moreover, in refrigerating chambers, only two parameters are mainly set - temperature and air velocity. The controlled parameter is mainly temperature. Relative humidity is a self-adjusting parameter, therefore, all recommendations for maintaining it within the desired limits are only a reflection of the conditions under which this value is independently established in the refrigerated volume.
The value of relative humidity is the result of the combined effect of many factors affecting its establishment; product properties, package availability, chamber dimensions, type of cooling device, storage temperature, etc.
The storage temperature of most refrigerated products lies in the temperature range -2.. .+ 2 °C. Some vegetable products (tomatoes, melons, etc.) are stored at higher temperatures, and more labile products containing fats are stored at lower temperatures.
Storage chilled meat in the form of half-carcasses, quarters, the process of autolytic changes, called maturation, continues. At 0 °С, the duration of meat maturation is 8-10 days, at 10 °С - 5 days, at 17 °С - 3 days. -0.2 m/s and relative humidity 85-90%.
Half carcasses are placed in chambers in a suspended state on overhead tracks. Since the surface of the meat is not moisture insulated, it, like any capillary-porous body with a wet surface, will evaporate moisture into environment. Evaporation is the greater, the greater the difference in the moisture content of the air near the surface and in the air of the chamber, and the more intensively it moves near the surface of the product. Therefore, in order to reduce shrinkage in meat storage chambers, convective air movement is used.
The shelf life of chilled meat depends on the season, the condition of the animal before slaughter, fatness, as well as the sanitary and hygienic condition of the carcass, refrigeration and storage chambers, etc.
It is effective to store meat in hermetically sealed packaging in a carbon dioxide atmosphere with a slight overpressure at a temperature of 1 ° C and for up to several weeks. Storing meat in a gaseous atmosphere eliminates color change.
The use of a modified gaseous environment (20% CO 2 and 80% O 2) during storage of ground beef delays the development of anaerobic microflora and increases the duration of its storage up to 4 days. at a temperature of 2 °C, at 0 °C - up to 8 days.
supercooled meat with a temperature throughout the volume of carcasses and half carcasses of -2 ... -1 ° C, they are stored in a suspended form. Permissible shelf life of chilled meat in air at a temperature of -1.5 ... 0 ° C, depending on the type and condition of the meat, is 7-12 days, supercooled - up to 17 days.
The shelf life of meat can be increased by lowering the storage temperature (down to -2 °C). However, the use of near-cryoscopic temperature during meat storage requires the use of reliable technical means of controlling this temperature.
by-products refrigerated can be stored for no more than 3 days. To increase the shelf life of by-products, they are frozen. The storage regimes for frozen offal are similar to the temperature regime for storing frozen meat.
Chilled bird stored in boxes stacked in stacks with gaps between containers for free air movement, which should be at least 4-6 volumes per hour. Storage temperature 0...+4 °С, relative humidity 80-85%. The shelf life of a slaughtered bird under these conditions is 4-5 days.
Frozen poultry stored for several months. The maximum shelf life of frozen poultry at a humidity of 85-90% is: unpacked carcasses of chickens, chickens, turkeys at air temperature
–25 °С - 11 months, packaged - up to 14 months. The deadlines for storage of unpacked geese, ducks at an air temperature of -25 ° C are
11 months, packed - up to 12 months.
chilled fish stored in boxes with ice. The shelf life is no more than a day. In refrigerators at temperatures
-2...0 °С and humidity 90-95% - no more than 2 days. Lightly salted, spicy and pickled fish are stored for up to 10 days. in jellied barrels at a temperature of -1...+1 °C, cold-smoked fish, dried balyk products at an air humidity of 75-80% and a temperature of -2...0 °C - up to 7 days, at 0... +4 °С - up to 4 days.
Canned fish natural products are stored at a temperature of 0...+10 °C for 6-24 months. respectively; canned fish in oil is stored at a temperature of 0 ... +20 ° C for 12-24 months. respectively; canned fish in tomato sauce stored at a temperature of 0...+5 °C for
6-18 months respectively.
Fish preserves stored at -1...+1 °C and humidity
70-75% for 10 days, at a temperature of +4...+6 C - for 3 days.
Shelf life frozen fish significantly depend on its individual properties, condition, cutting method and freezing method.
Fish, predominantly of marine species (up to 85% of all types of fish caught), are butchered and frozen on fishing vessels. As a rule, due to large one-time trawl catches with limited capacity of freezers, fish are pre-cooled with ice. The simplest way to solve the problem of the safety of the catch is to freeze the fish without cutting it first. The disadvantage of the method is that subsequently the fish is thawed at the fish processing plant, gutted and part of it is re-frozen again. However, according to the International Institute of Refrigeration (IIH), repeated freezing of fish does not significantly impair its quality.
In the frozen state, the fish has a reduced safety. The change in its properties is determined by the rancidity of fats and denaturation changes in proteins. When the fish goes rancid, its aroma and taste deteriorate. In addition, the tissue structure is destroyed, the consistency of the fish changes.
An increase in the shelf life of frozen fish is achieved by using various methods of its processing, for example, glazing the fish (applying ice to the surface of the product), applying a film of thermoplastic waxes to the surface of the fish, vacuum packaging the fish, etc. The latter method allows you to increase the shelf life by 3-4 months.
Eggs stored mainly in cardboard boxes at a temperature of -2 ... 0 ° C and a relative humidity of 85%. Storage of eggs at a temperature of -2 ° C allows them to be preserved for up to 6 months.
In principle, it is possible to lower the storage temperature of eggs to -2.5 °C and store them in a supercooled state. However, the supercooled state is unstable. In the absence of proper temperature control, eggs can be frozen.
egg products stored in a frozen state, packed in containers that prevent the access of oxygen to the surface of the product (metal cans, cardboard boxes with liners made of polyethylene film or laminates). The storage temperature is -25...-12 °С. Accordingly, the duration of refrigerated storage is from 8 to 15 months.
Animal rendered fats(beef, mutton, pork) are stored in wooden barrels and boxes at a temperature of 0 ... + 6 ° C for no more than a month, in sealed metal and glass jars - up to 18 months.
Terms and conditions of storage butter determined by its type and method of production and temperature conditions.
The shelf life of most varieties of butter is not significantly affected by temperature. The average period of refrigerated storage of peasant butter is from 1 to 3 months, in particular sour cream butter - up to 6 months.
3.4 Cooling devices for storage rooms
The necessary temperature and humidity conditions in the storage chambers can be created the right choice cooling systems. Storage chambers for chilled meat products are equipped with wall-mounted direct-cooling batteries and air coolers; storage rooms for eggs, fruits, vegetables - dry air coolers with increased air circulation; chambers for long-term storage of frozen products (meat, fish, pork, etc.) - with wall and ceiling direct-cooling batteries.
On the surface of the cooling batteries, moisture from the air condenses in the form of frost and drops. A decrease in air humidity and partial pressure of water vapor leads to the evaporation of moisture from the surface of the product, i.e. to dry him out. With insufficient thermal insulation of the refrigerator, heat inflows into the chambers become larger, the surface of the cooling batteries increases and, accordingly, the shrinkage of the product increases. Therefore, the quality of insulation, as already noted, must be high.
To reduce shrinkage, cooling devices are placed on those fences through which there are heat inflows. Beam batteries placed in the central aisle refrigerator compartment under the ceiling (in 6 ... 8 rows in height), did not justify themselves (great unevenness of the temperature regime, increased air circulation in the cargo volume, causing a large shrinkage of the products).
To reduce external heat inflows and maintain an increased relative humidity of the air, storage rooms for frozen products are sometimes arranged with a heat-protective air jacket. The latter is a free space (0.6 m wide) allocated from the side of the outer walls with the help of partitions with waterproofing. Cooling devices are placed in this space to extinguish external heat inflows. With such a system, there is no heat exchange between the chamber air and the fences (the same temperature). Small batteries are installed in the chamber itself to extinguish only internal heat inflows (from the stay of people, etc.). The shrinkage of the products is thus significantly reduced.
The panel cooling system is efficient and economical, in which the chamber air temperature is close to the boiling point of the refrigerant in the batteries, and the relative humidity is close to 100%.
3.5 Practical task
