What determines the shelf life of milk
Packages often contain terms that we do not know or misunderstand: “Normalized milk was used”, “Ultra-pasteurized”, “Made from whole milk” and so on. Let’s deal with varieties of milk raw materials, ways of its processing and packaging, and how all this affects the longevity of dairy products.
Milk raw materials
According to GOSTs milk can be:
- One-piece. This is natural milk, which was filtered, but not regulated by fat. The natural balance of fats, proteins and carbohydrates in such milk is unchanged.
- Normalized. This milk, divided into a reverse (liquid with zero fat content) and cream, and then restored to the desired 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.
- Low-fat. This is milk, from which cream is separated during the separation process. To taste it is almost the same as the whole, but the energy value is half as low. Such milk and products based on it are produced for people who count calories.
- Recovered. It is milk made from concentrated or powdered milk and water.
Method of processing
Depending on the heat treatment, milk is divided into:
- Pasteurized – One-time heating is usually up to 60 ° C. When pasteurized, the vegetative forms of microorganisms die, but their spores remain viable and, if favorable conditions develop, develop intensively. As a rule, pasteurized whole or skim milk, as well as cream and buttermilk. Pasteurized products are stored at low temperatures for a short period of time.
- Ultra-pasteurized – short heating up to 150 ° C and rapid cooling. Bacteria that lead to the souring of milk, die, but the taste and nutrients remain.
- Sterilized – fairly long heating up to 100 ° C and above. In fact, this boiled milk, in which no useful substances remained and all the bacteria, including lactic acid, died. Neither curdled milk, nor cottage cheese from it will not work. But this milk can be stored for a very long time. In the manufacture of sterilized and ultra-pasteurized milk, various salt-stabilizers are often used.
Based on the above classifications, all dairy products can be divided into short and long.
Short milk is unreduced milk with a low pasteurization temperature, as well as products made on its basis. Long milk is ultra-pasteurized and sterilized or reconstituted from milk powder and products that are made from it.
In addition to raw materials and processing methods, the type of packaging affects the shelf life of milk.
- Soft packing (fin-pak, berta-pak and others). These are bags of high-strength polyethylene.
- Semi-rigid packaging (various types of thermoplastics). It is, as a rule, a plastic cup with a sealed “lid” made of foil or film.
- Semi-rigid packaging of sheet and combined materials (tetra-pak, tetra-rex and others). These are cardboard boxes of various shapes with multi-layer coating inside.
Companies working with short milk, usually choose polyethylene, plastic and cheap options for cardboard packaging. If on the counter milk in a plastic bag and a paper bag, most likely, you have pasteurized milk with a shelf life of 3-5 days.
Thermoplasts are most often used for yoghurts, sour cream and other fermented milk products. The most important thing here is the tightness of the packaging. If the manufacturer used high-quality coating material and strictly followed the gas environment during packaging, the product will be easily stored for 5-7 days.
Have you seen the smallest hole in the foil? 99% that the product is spoiled.
Ultrapasterization and sterilization requires an aseptic spill, which can only provide tetra-pack. Do not buy such milk in plastic bags and a cheaper carton.
How much to store milk and sour-milk products
Taking from the counter a bottle of milk or a pack of kefir, we first look at the expiration date and wonder why such a spread? The product of one brand lives only a couple of days, but it seems to be exactly the same product, but another brand – two weeks.
The shelf life of dairy products is determined by the manufacturers. However, it should not exceed the time limits prescribed in the regulatory documents of the regulatory bodies.
The shelf life of milk, which is only slightly heated to bring to consumers, can not exceed 5 days. The shelf life of sour-milk products without stabilizers and preservatives is no more than 10 days.
The shelf life of the long milk is established by the producers based on which stabilizers, preservatives and thickeners are added to the composition. The manufacturer must pass the testing and approve the storage period for each product in Rospotrebnadzor. Therefore, the consumer should be guided by the date indicated on the package.
The optimum temperature of storage of short milk is 2-4 ° С. This is the third shelf of the refrigerator, as well as the area of freshness. Long milk can be put on the upper shelves and even the refrigerator door. For sterilized milk in the package, for example, the storage temperature is allowed up to 25 ° C.
After opening the package, the maximum shelf life of the pasteurized milk is 48 hours, sterilized milk – 96 hours. Ultra-pasteurized stored as much as written on the package. Sour-milk products should be consumed within 72 hours.
How to determine the freshness of milk
Sometimes the deadline did not come out, and you keep it in the fridge, but you still take doubts: is it possible to eat it? Determine the adequacy of the product can be not only in terms of storage, but also by external characteristics.
Fresh milk is white, homogeneous, without flakes, loose lumps of fat and extraneous tastes and smells (except that in baked and sterilized there is a taste of boiling).
If the milk is fat (4.7% and higher), the formation of a characteristic film is permissible, which immediately disappears with mixing. Skim milk may have a slightly bluish tint, and sterilized milk – cream.
A sour milk is felt in the sour milk, and then a clot appears. It turns into curdled milk.
How to determine the freshness of yogurt and yogurt
Fresh yogurt has a uniform consistency. Due to mixed (lactic and alcoholic) fermentation and a special starter on kefir fungi, gas formation is possible. Natalia Klimova notes that a slight swelling of the package with kefir is normal.
But for a burger it is, on the contrary, a sign of spoilage. The product is produced by fermenting melted milk with the addition of special starter cultures. Fresh ryazhenka absolutely homogeneous, gentle cream color and with a pleasant melted aftertaste.
The main sign of spoilage of dairy products is the appearance of watery serum from the top.
How to determine the freshness of sour cream
Fresh sour cream should be homogeneous, thick, with a white or slightly creamy glossy surface. The minimum mass fraction of fat for sour cream is 10%, the maximum – 42%. The higher the fat content, the thicker the sour cream.
According to GOST, stabilizers and thickeners can not be added to sour cream. If the manufacturer has sprinkled some powders, he has no right to write on the package the word “sour cream”. Therefore, in stores there were all kinds of sour cream, sour cream products. They are cheaper than natural sour cream, but you need to carefully study the composition: whether there are any foreign additives.
How to determine the freshness of yogurt
Natalia Klimova explained that, depending on the way of production, yogurt can be liquid (drinkable) and creamy. In any case, the consistency of the fresh product should be uniform. With a tank method of production (this is when the product is first fermented in a large container and then bottled into a container), the protein clot of the product can be disturbed. When thermostatic (when the ferment is introduced into the already packaged product), the clot must be whole.
If yogurt with pieces of fruit, then it should be moderately sweet and match the color and flavor of the filler.
How to determine the freshness of cottage cheese
Fresh product is soft, it has a smearing or crumbly consistency. For low-fat cottage cheese, a small amount of whey and a slight aftertaste of dried milk is normal.
Spoiled cottage cheese is easy to recognize to taste: it bitter.
What to do if the milk is spoiled
Do not worry if the deadlines missed. Natural milk can be processed into kefir or yogurt. To do this, you need to buy a special starter and mix it with a heated sour product.
If the whey or milk begins to peel off the whey, make a cottage cheese. To do this, the liquid also needs to be heated, but do not bring to a boil, so that the flaked cottage cheese is separated from the whey, and thrown back to a colander, covered with gauze. After that, gauze should be tied and hung over the sink to the remaining liquid glass.
Also a little sour milk and a little overdue kefir – an excellent basis for pancakes.
- 1 What determines the shelf life of milk
- 2 How much to store milk and sour-milk products
- 3 How to determine the freshness of milk
- 4 How to determine the freshness of yogurt and yogurt
- 5 How to determine the freshness of sour cream
- 6 How to determine the freshness of yogurt
- 7 How to determine the freshness of cottage cheese
- 8 What to do if the milk is spoiled