How and how much to store milk and dairy products

2024 Author: Malcolm Clapton | [email protected]. Last modified: 2023-12-17 03:44

Lifehacker talked to a milk production technologist and found out what determines the shelf life of milk, kefir, fermented baked milk, yogurt, sour cream and cottage cheese.

What determines the shelf life of milk

There are often terms on the packaging, the meaning of which we do not know or do not understand: “Normalized milk used”, “Ultra-pasteurized”, “Made from whole milk” and so on. Let's take a look at the types of raw dairy products, how they are processed and packaged, and how all of this affects the lifespan of dairy products.

Dairy raw materials

According to GOSTs, milk is:

1. Solid … This is natural milk, which has been filtered, but not regulated in terms of fat content. The natural balance of fats, proteins and carbohydrates in such milk is unchanged.
2. Normalized … This is milk, divided into return (liquid with zero fat content) and cream, and then reconstituted to the required parameters. Milk is normalized so that it is not too fat and to make sour cream, cottage cheese and other products with a certain percentage of fat.
3. Fat free … This is milk from which the cream is separated during the separation process. It tastes almost the same as whole, but its energy value is half as much. Such milk and products based on it are produced for people counting calories.
4. Restored … This is milk made from concentrated or powdered milk and water.

Processing method

Depending on the heat treatment, milk is divided into:

1. Pasteurized - one-time heating, usually up to 60 ° С. During pasteurization, vegetative forms of microorganisms die, but their spores remain viable and develop intensively when favorable conditions arise. Typically, whole or skim milk is pasteurized, as well as cream and buttermilk. Pasteurized products are stored at low temperatures for a short time.
2. Ultra-pasteurized - short heating up to 150 ° C and fast cooling. The bacteria that lead to sour milk die, but the taste and nutrients remain.
3. Sterilized - rather long heating up to 100 ° C and above. In fact, this is boiled milk, in which there are no nutrients left and all bacteria, including lactic acid, have died. Neither curdled milk nor cottage cheese will come out of it. But such milk can be stored for a very long time. In the manufacture of sterilized and UHT milk, various stabilizing salts are often used.

Based on the above classifications, all dairy products can be conditionally divided into short and long.

Short milk is unrecovered milk with a low pasteurization temperature, as well as products based on it. Long milk is UHT and sterilized or reconstituted from powdered milk and products that are made from it.

Package

In addition to the raw materials and the processing method, the type of packaging affects the shelf life of milk.

1. Soft packaging(fin-pack, berta-pack and others). These are bags made of polyethylene of increased strength.
2. Semi-rigid packaging(various types of thermoplastics). It is, as a rule, a plastic cup with a sealed "lid" made of foil or film.
3. Semi-rigid packaging from sheet and combined materials(tetra-pack, tetra-rex and others). These are cardboard boxes of various shapes with a multilayer coating inside.

Short milk companies typically choose polyethylene, plastic, and cheap carton options. If there is milk on the counter in a plastic and paper bag, most likely you are looking at pasteurized milk with a shelf life of 3-5 days.

Thermoplastics are most often used for yoghurts, sour cream and other fermented milk products. The most important thing here is the tightness of the package. If the manufacturer has used quality coating material and strictly monitored the atmosphere during packaging, the product will easily be stored for 5-7 days.

Did you see the slightest hole in the foil? 99% that the product is spoiled.

Ultra-pasteurization and sterilization requires aseptic filling, which only Tetra-Pak can provide. You should not buy such milk in plastic bags and cheaper cartons.

How much to store milk and fermented milk products

Taking a bottle of milk or a pack of kefir from the counter, we first look at the expiration date and wonder why there is such a spread? The product of one brand lives only a couple of days, but it seems to be exactly the same product, but of another brand - two weeks.

The shelf life of dairy products is set by the manufacturers. However, it should not exceed the terms prescribed in the regulatory documents of the regulatory authorities.

The shelf life of milk that has only been slightly heated to deliver it to consumers cannot exceed 5 days. The shelf life of fermented milk products without stabilizers and preservatives is no more than 10 days.

The shelf life of long milk is set by manufacturers based on which stabilizers, preservatives and thickeners are added to the composition. The manufacturer is obliged to undergo testing and approve the shelf life for each of its products in Rospotrebnadzor. Therefore, the consumer needs to be guided by the date indicated on the package.

The optimum storage temperature for short milk is 2–4 ° С. This is the third shelf of the refrigerator and also the freshness area. Long milk can be placed on the top shelves and even on the refrigerator door. For sterilized milk in packaging, for example, a storage temperature of up to 25 ° C is permissible.

After opening the package, the maximum shelf life of pasteurized milk is 48 hours, sterilized milk is 96 hours. UHT is stored for as long as it is written on the package. Fermented milk products should be consumed within 72 hours.

How to determine the freshness of milk

Sometimes the deadline has not expired, and you keep it in the refrigerator, but still they take doubts: is it possible to eat it? It is possible to determine the adequacy of a product not only by shelf life, but also by external signs.

Natalya Klimova Chief Technologist SAPK-Milk (Podvorie holding)

Fresh milk is white, homogeneous, without flakes, stray lumps of fat and foreign tastes and odors (except that baked and sterilized milk has a boiling flavor).

If the milk is fatty (4, 7% and more), the formation of a characteristic film is permissible, which immediately disappears upon stirring. Skim milk can have a slightly bluish tint, while sterilized milk can be creamy.

Sour milk feels sour, and then a clot appears. It turns into yogurt.

How to determine the freshness of kefir and fermented baked milk

Fresh kefir has a uniform consistency. Due to the mixed (lactic and alcoholic) fermentation and special fermentation on kefir fungi, gas formation is possible. Natalya Klimova notes that a slight swelling of the kefir package is normal.

But for fermented baked milk, this, on the contrary, is a sign of spoilage. The product is produced by fermenting baked milk with the addition of special starter cultures. Fresh fermented baked milk is absolutely homogeneous, light cream in color and with a pleasant melted aftertaste.

The main sign of deterioration of fermented milk products is the appearance of watery whey on top.

How to determine the freshness of sour cream

Fresh sour cream should be smooth, thick, with a white or slightly creamy glossy surface. The minimum mass fraction of fat for sour cream is 10%, the maximum is 42%. The higher the fat content, the thicker the sour cream.

Natalia Klimova

According to GOST, stabilizers and thickeners cannot be added to sour cream. If the manufacturer poured in some powders, he is not entitled to write the word "sour cream" on the package. Therefore, all kinds of sour cream and sour cream products appeared in stores. They are cheaper than natural sour cream, but you need to carefully study the composition: are there any outsiders inside.

How to determine the freshness of yoghurt

Natalia Klimova explained that depending on the method of production, yoghurt can be liquid (drinking) and creamy. In any case, the consistency of the fresh product must be uniform. With the reservoir method of production (this is when the product is first fermented in a large container, and then poured into a container), the protein clot of the product can be disrupted. With a thermostat (when the starter is added to an already packaged product), the curd must be intact.

If yogurt is with pieces of fruit, then it should be moderately sweet and match the filler in color and aroma.

How to determine the freshness of curd

The fresh product is soft and has a smearing or crumbly texture. For skimmed curd, it is normal to have a little whey and a faint taste of milk powder.

Natalia Klimova

Spoiled cottage cheese is easy to recognize by its taste: it tastes bitter.

What to do if the milk goes bad

Do not be upset if you missed the deadline. Natural milk can be processed into kefir or yogurt. To do this, you need to buy a special starter culture and mix it with a heated sour product.

If whey begins to flake off in kefir or milk, make cottage cheese. To do this, the liquid also needs to be heated, but not brought to a boil, so that the cottage cheese flakes separate from the whey, and put it in a colander covered with gauze. After that, the gauze needs to be tied and hung over the sink to drain the remaining liquid.

Also, slightly sour milk and slightly expired kefir are an excellent base for pancakes.