dairy cold storages are not just about storing milk. As Highend, we are always ready for more detailed information and solutions on the subject. Absolutely do not hesitate to call us.

Cold Storage of Raw Milk

Undoubtedly, microorganisms are the most important factors that play a role in the deterioration of milk. Microorganisms contaminating milk from different sources cause various fermentations and decompositions, and as a result of these activities, changes are observed especially in the sensory qualities of milk. The activity of microorganisms in milk makes it difficult to process milk into various dairy products, and sometimes it can lead to dangerous diseases and epidemics.

Since it is inevitable for milk to be contaminated by microorganisms, the main way to preserve its natural quality is to curb the bacterial activity. For this, it is necessary to immediately cool the milk below 10°C as soon as it is milked, and to remove it from the heat where bacterial activity is intense. However, the activity of psychrophilic bacteria prevents long-term storage even below 4°C. For this reason, the best cooled milk should be processed and transformed into a product no later than 24 hours after the first milking. Because the coagulation times of milk stored at low temperatures are prolonged with rennet, and when cheese is made from such milk, especially the whey is separated late, the clot loosens and it becomes difficult to process. However, these drawbacks can be largely eliminated by adding CaCl _{2 to the milk processed into cheese.} On the other hand, free fatty acids increase during cold storage and especially those with 6, 8, 10 and 12 carbons cause bitterness in milk and butter. The cooling rate of the milk also affects the hydrolysis events. For example, hydrolytic degradation is minimal when milk is cooled from 30°C to 5°C in 10 seconds, whereas it reaches very high levels when the cooling time is 25 minutes. Mixers in cooling tanks also accelerate the lipolysis event. As a result of mixing, large fat globules are broken down and lipase enzyme activity increases. In addition, during cooling, the mineral balance between the soluble and colloidal salts of the milk changes, and in this case, the coagulation times of the milk to be processed into cheese are prolonged, the clot becomes loose and the losses increase.

Although it is an obligatory process to store the milk by cooling in tanks and buckets until it is evaluated, and also to transport it from the production sites and milk collection centers to the factories, as mentioned above to some extent, cooling causes negative changes in the structure of the milk after a certain period of time, and such milk is of standard quality. It is seen that there are problems in the production of drinking milk and dairy products.

In order to minimize the changes in milk during cold storage, the following can be recommended:

• The time between morning and evening hours should be shortened.
• Milk should be cooled as soon as possible after milking.
• Care should be taken not to freeze the cooled milk.
• The slide should not be stored in the cold for more than 1-2 days.
• Mixing of milk should be done very quickly.
• The time until the milk is processed into products should be minimized.

Cold Storage of Drinking Milk

When drinking milk is mentioned, mostly pasteurized and sterilized, in other words, heat treated milk is understood.

During the storage, transportation and consumption stages of heat treated milk, microorganisms, xanthine oxidase and similar enzymes, light and oxygen can change the ingredients, smell and taste of milk. For this reason, milk should be protected from sunlight, especially ultraviolet rays, during storage. In order to protect the milk from the negative effects of light, the warehouses should be made in a way that does not leak light. Protection of milk against both sun and artificial light can be achieved with opaque packaging and brown glass bottles. Storing sterilized milk at +4°C - 10°C increases its lifespan. However, a sterilized milk obtained by the UHT method will last for at least 1.5 months at 15°C - 20°C without losing its quality, and at least 3 months at 15°C - 20°C for the milk sterilized by the conventional method.

Cold Storage of Yogurt

Dairy products such as yoghurt and buttermilk become unusable over time due to the proliferation of microorganisms such as mold, yeast and L. bulgaricus, the emergence of bitterness with enzymatic activities, the change in the water holding capacity of proteins as a result of some chemical changes and the oxidation of fat. For this reason, the storage period of sour milk products is very limited. If the yogurt is produced under hygienic conditions;

• Less than 1 week at +7°C / +10°C,
• 1-2 weeks at +5°C,
• 3 - 6 weeks at 0°C / +1°C

may have a storage life of up to

Freezing yoghurt for longer storage does not give positive results. Although there are no significant changes in the biological properties of yoghurts stored by freezing, their sensory qualities, especially the structure, are significantly impaired as a result of thawing.

Storage of Condensed Milk and Products

Condensed milk and products can be stored for 2-3 years at +15°C. Longer storage at higher temperatures may cause gelation and agglomeration in such products.

It is also possible to store condensed milk for a long time by freezing it. Such practices have been made in the past years, especially during war times. However, various sensory, physical and chemical deteriorations occurred in milk stored in frozen condition for a long time, as in normal milk.

Storage of Dried Dairy Products

The less water there is in the dried dairy products and the lower the water activity; microbiological and enzymatic activities and chemical events are extremely slow. In most cases, it is necessary to store dried milk and its products at low temperatures. Namely; as it is known, milk powders obtained at high degrees for bakery products; Powders with moderate heat treatment are used in the production of reconstituted thickened milk, and those produced at low temperatures are used in the manufacture of reconstituted drinking milk and cheese from reconstituted milk. Here are the milk powders obtained by low heat treatment and containing fat. It should be cooled immediately after drying.

A skim milk powder produced in accordance with its technology and packed with air, water vapor and opaque material or packed with an invert gas can be stored at 15°C for 2 years without losing its quality. The maximum storage period for this type of dairy product is 4 years. On the other hand, this period is 1-3 years at 15°C in whole milk powders.

Storage of Ice Cream

Ice cream is a dairy product obtained by adding sugar, mortar and flavoring substances, sometimes eggs, and freezing the milk enriched with the composition.

Ice creams can be classified into two main groups according to their consistency:

• soft ice creams
• Hardened ice creams

Soft ice cream is offered for consumption at -5°C, -7°C as it comes out of the ice cream machine; hardened ice cream is ice cream that is hardened in deep freezing machines, for example, in cold tunnels to -20°C, -30°C. In soft ice creams, only 30%-50% of the water contained is frozen, whereas in hardened ice creams this rate reaches 80%-90%. This makes it easier to transport and store ice cream. The important thing here is to ensure the formation of small crystals in ice cream and to prevent the formation of larger crystals during storage. Thus, a smooth and polished structure effect can be achieved on the tongue. As is known, a small and stable crystallization can be achieved with a large freezing rate.

Besides, taking advantage of very low temperature in the freezing process, intensive mixing process, high total dry matter ratio of the ice cream mix and the addition of some auxiliary substances are the factors facilitating the achievement of the goal. In order to obtain fine, small crystals, it is also useful to inoculate crystals into the liquid ice cream mixture before freezing. For this, it is sufficient to return a long section from the freezing device to the pre-cooled mix.

Ice creams, whose hardening process is completed, can either be offered for immediate consumption or stored for months at -20°C, -25°. For more detailed information, you can review the Ice Cream Cold Storages page in our activity areas section.

Storage of Cheese

It is necessary to deal with the cold storage of cheese in sections:

• Cold storage at the ripening stage,
• Cold storage for the preservation of ripened cheese.

As known; The period of waiting for a while in very cool conditions and gaining flavor, smell, appearance and consistency specific to its variety is called ripening. Ripening is done many times, in quality and in batches, on the shelves. Sometimes, raw cheese completes its maturation in brine placed in tins. The most important factor in cheese ripening is the determination and control of the appropriate temperature and relative humidity. Temperature, in fact, has an effect on ripening and thus cheese quality, as it regulates the activities of microorganisms that enable ripening. The temperature suitable for the growth of lactic acid bacteria is not conducive to the growth of propionic acid bacteria. For this reason, temperature changes are made gradually. This situation, which is of great importance in cheese ripening, also plays an important role in the storage of ripened cheese. In hard cheeses, as the temperature decreases, ripening usually slows down and the quality of the cheese increases. However, the temperature should not fall to a level that will spoil the structure of the cheese. -10°C is the critical point in the deterioration of the structure of hard cheese. Soft cheeses ripen at higher degrees than hard cheeses. Although the ripening temperatures vary according to the cheese type, they are between +8°C and +10°C. The required relative humidity is 75% - 85% for fresh hard and semi-hard cheeses, and 80% - 90% for aged hard and semi-hard cheeses.

Maturation period: 3 - 10 months for hard cheeses; 5 - 10 weeks for semi-hard cheeses; It is 3 - 6 weeks for soft cheeses.

As explained above, in cold storage for preservation purposes, temperature and humidity play an important role. There is a great difference in durability between cheese groups in the storage of cheeses without losing their quality.

Storage temperatures of cheeses after ripening are generally +4°C, +5°C; Moisture demands are between 90-95% in shelled cheeses and 60-70% in packaged unshelled cheeses. In processed cheeses, the storage temperature varies between +10°C and room temperature, and the lifespan increases as the temperature decreases.

Storing the cheese frozen is of no practical importance. Because, negative and extreme deviations occur in the sensory, physical and chemical properties of cheeses processed in this way.

Cold Storage of Cream

If milk cream is not to be processed into ice cream or butter within a few hours and is to be kept for a while, it should be cooled and stored immediately. In such cases, it is recommended that the cooling degree be +40°C. However, if it is to be stored for a long time, it should be pasteurized at high temperatures and stored at at least -20°C.

Considerations in Freezing Cream

• The fat ratio of the cream to be frozen should be 40-50%. More can lead to oil leakage.
• Cream whose fat ratio is adjusted to the specified level should be pasteurized. It is sufficient to perform the heat treatment at 95°C, 102°C for 15 seconds.
• Pasteurized cream should first be cooled to about 5°C and then frozen quickly.
• The cream to be frozen should be frozen in blocks of approximately 15-30 kg in polyethylene bags, if possible in polyethylene bags lined with parchment paper and in vertical plate ice cream machines at -35°C. Polyethylene bags are a packaging material that can protect cream from sublimation and surface oxidation.
• Air should be avoided during the freezing process, and contamination of metals such as Fe, Cu, which catalyze oil degradation, should be avoided.
• If the cream is to be stored in stainless steel containers, care should be taken to ensure that the lids of these individual containers are tightly closed and that the frozen cream is not filled to the brim to prevent the container from bursting due to the volume change.
• Storage temperature should be at least -20°C. However, the most suitable storage temperature is -30°C, -35°C. Creams stored at the specified temperatures can maintain their quality for 12-24 months.

Cold Storage of Butter

The purpose of storing butter is based on social and economic reasons, to meet the consumption in the months when production is insufficient and to prevent price drops caused by the supply-demand imbalance.

Butter Storage Conditions and Methods

If the butter obtained in the factory is to be stored for a short time, it is stored in +6°C, +8°C warehouses. However, butter is usually not molded and packaged immediately after its production. It is stored for 6 months at -15°C, -20°C in 20-25kg barrels or in larger heaps.

Butter Storage Time

Butter durability; It varies according to the storage temperature, water distribution, acidity of the cream it is processed, microbial and chemical contamination, the quality of the package material and packaging method.