The term "pasteurization" is derived from the name of the French scientist Louis Pasteur, thanks to his work in combating the microbes by heat treatment. It is interesting, however, that Pasteur's sphere of interests was wine and beer, not milk. Only in 1886 the chemist Franz von Soxhlet was the first to propose the pasteurization of all milk that goes on sale.
Pasteurization is a method of preserving food products, especially liquid ones, a heat-treatment process at temperatures below 100 ° C, usually about 60-70 ° C, followed by a sudden cooling to 4-6 ° C. Pasteurization destroys pathogenic microorganisms in certain foods and beverages. In case of milk, these are such bacteria as E. coli, Salmonella and Listeria.
Methods of pasteurization
The efficiency of the pasteurization process depends on two factors: the heating temperature and the period of the process (the higher the heat treatment temperature is, the shorter is the duration, and vice versa). Therefore, there are several pasteurization methods that can be used to produce milk:
- long pasteurization, the milk is heated at a temperature of 63-65 ° C for several minutes;
- short-term pasteurization, the milk is heated at a temperature of 71-74 ° C for 15-20 seconds;
- high, or instant pasteurization, the milk is heated at 85-87 ° C, instantly or within a few seconds.
Another method is the pasteurization at ultra-high temperature (UHT) at 80-95 ° C. The advantage of this method is that it destroys most of the microbes (99.9%) from raw milk and provides a longer shelf life. But on the other hand, such treatment reduces the ability of coagulation, contributing to the formation of a soft layer with the maximum introduction of serum. Also in case of UHT, the vitamin content decreases (B12, ascorbic acid) and sometimes the process causes caramelization of milk through the formation of melanoid substances.
Advantages and disadvantages of pasteurization
Pasteurization allows us to deliver products over long distances and store them for a longer period of time. Standard pasteurization increases milk storage for one or several weeks, while aseptic UHT milk can be stored for up to 10 months.
Pasteurization of milk does not guarantee that it will not contain any bacteria, because microorganisms such as Listeria can survive at temperatures up to 70 ° C, This bacteria is very dangerous and may cause meningitis, intrauterine infections or spontaneous abortions. On the other hand, milk may be contaminated with pathogenic microorganisms during transportation or storage.
Despite the fact that pasteurization is an effective method of food storage, this technology is often subjected to criticism. Over the years, it has been argued that heat treatment destroys vital nutrients in milk. The debate about the pros and cons of pasteurization continues today.
* Pasteurization is also used for other products, such as fruit juices, beer, compotes, tomato paste, meat, cakes, honey, etc.
The packaging of milk and dairy products is designed to protect them from oxygen and moisture. It provides freshness and increases the shelf life of dairy products and must comply with strict food safety requirements. Usually in stores we find milk packed in plastic bottles or bags, cardboard boxes and less often, in glass bottles.
Plastic bottles or bags
Plastic bags are quite common and usually have the form of pillows, they are made of low density plastic film. Another common packaging is plastic bottles, PET with different capacities. Plastic is used to store fresh and pasteurized milk, and the material from which these containers are made should be colored to reduce light transmission. PET is generally recognized worldwide as a non-toxic, safe, lightweight, durable, flexible, microwave-resistant product. The disadvantage of this material is that it hardly decomposes, and the probability that the bottles will be recycled is very small.
TetraPak cardbord packages are easily stored in the refrigerator, keep the milk fresh and come in different sizes. The used material is a polyethylene film deposited on pressed paper and aluminum foil in case of aseptic products. This type of packaging can be recycled 100%. TetraPak used for milk packaging consists of several layers: cardboard 75%; aluminum foil 5%; polyethylene food 20%. The disadvantage of this packaging: it is sensitive to moisture and breaks easier.
Glass bottles are less common than plastic or cardboard packaging, although glass is a reliable product that is 100% recyclable. It is impermeable, so there is no contact between the product and the glass, which could affect the taste of milk, ensuring the fact that the product retains its properties and flavor. Disadvantages: the glass is heavy and fragile. Despite this, several international surveys among consumers have shown that glass is the packaging material that is best suited for milk.
This article is part of a series of materials published within the frame of Drumul Laptelui campaign, launched by Madein.md in partnership with the Public Association "Pro Cooperare Regională", the project ”Milk Market Improvement through Linkages and Knowledge (MILK)”.