Radiation sterilization of medical devices. Sterilization of medical products. Requirements for validation and ongoing control. Radiation sterilization. Features of the use of biological indicators of sterilization

In world practice, the method of radiation sterilization for food products began to be mastered about 15 years ago. Then it was discovered that the traditional methods of food sterilization - treatment with sulfur dioxide and others - are harmful to the ozone layer of the Earth. A fundamentally new technique was proposed - irradiation with gamma rays from radioactive sources, electrons in particle accelerators or high-energy x-rays. The method turned out to be effective - the products did not spoil, retained their taste and appearance. It has been approved by the World Health Organization, subject to strict controls. According to the WHO recommendation, all manufacturers are required to inform the consumer and indicate on the package a special sign - “radar” (Fig. 7), so that the buyer can choose whether he eats the irradiated product or not.

Fig.7. Radura sign

World scientists have not yet resolved the issue of the safety of the method of radiation sterilization. Studies have shown that when products are irradiated with an underestimated dose, sterilization becomes ineffective, since fungi and pathogens are not destroyed -

salmonella, vibrio cholerae and others. In turn, at a large dose, vitamins are noticeably destroyed, the amount of by-products, the so-called free radicals, which have a very high chemical activity, increases. While they are in the product, they do not manifest themselves in any way, but when they enter the human body and dissolve, they can cause a wide variety of reactions - damage the human genetic code, increase the risk of cancer and other diseases, cause premature aging, and much more, which was confirmed by experiments on laboratory animals.

5. PRESERVATION BY CHANGING THE PROPERTIES OF THE ENVIRONMENT

Preservation of food products can be carried out by changing the properties (composition) of the medium to a level that excludes the possibility of vital activity of microorganisms in food product. The high sensitivity of microorganisms to changes in osmotic pressure and the concentration of hydrogen ions (pH of the medium) is the basis for conservation by changing the medium.

PRESERVATION BY CHANGING (INCREASING) OSMOTIC PRESSURE

Canning is done by adding to the product sodium chloride or sugar to a concentration that prevents the development of microorganisms. The osmotic pressure of solutions of sodium chloride and sugar is quite high (6.1 atm. 1% solution). The osmotic pressure inside a bacterial cell is usually slightly higher than the pressure environment, which is necessary for the normal course of the processes of exchange of a microorganism with external environment. Raise osmotic pressure in the product leads to a violation of the exchange of microbial cells with the external environment. At the same time, an increased removal of water from the cell is noted, which leads to its dehydration, a decrease in the volume of protoplasm, its exfoliation from the membrane and death of the microbial cell. Thus, under the influence of sufficiently concentrated solutions of sodium chloride or sugar, water is taken away from the bacterial cell, and the protoplasm undergoes dehydration and plasmolysis.

Preservation by salting. When harvesting fish and some other products (meat, vegetables, etc.), salting is widely used.

The concentrations of sodium chloride used in salting are 8–12%, corresponding to 50–73 atm. osmotic pressure, which provides sufficient bacteriostatic and bactericidal effect. By increasing the osmotic pressure, sodium chloride simultaneously has a negative effect on the protoplasm of a bacterial cell (the effect of chloride ions) and on the conditions for the development of aerobic microorganisms by reducing the oxygen content in the tissues of the preserved product. The resistance of microorganisms to various concentrations of NaCl is different. Most microorganisms, including those of the intestinal group, stop growing at NaCl concentrations of about 10% . The causative agents of food toxic infections (Salmonella) and food toxicosis (Staphylococcus) are highly resistant to NaCl, which stop growing only at a concentration of NaCl in the product of 15–20%. Some microorganisms, called halophiles, are able to grow at very high concentrations of NaCl. They are often found in concentrated saline solutions ( brine), in which salting of fish is carried out. Among the halophilic bacteria there is a pigment-forming Serratia salinaria, during the development of which red pigment spots appear on salted fish.

Distinguished by nature dry and wet, and depending on the cooling warm and cold ambassador. With dry salting, the product is rubbed or rolled in salt and placed in barrels or vats without brine; the latter is formed as a result of diffuse-osmotic processes due to the water of the salted product. Wet or brine salting is made by immersing the salted product in a vat with a saturated NaCl solution prepared in advance. Warm salting is called, produced without cooling, at ambient temperature. Cold salting provides for the preliminary freezing of the salted product and the widespread use of the ice-salt mixture. In sanitary terms, the most acceptable ambassador with cooling.

Preservation by salting has a number of significant disadvantages. In the process of salting and in the future during the culinary processing of salted products, a significant amount of nutritious extractive substances, including nitrogenous and protein ones, is lost. Vitamins are almost completely destroyed. The consistency and taste of some salty foods (corned beef, salted fish, etc.) are deteriorating. When meat is wet salted, 2.14% of its proteins pass into brine and are irretrievably lost; in some cases, the loss of proteins during meat salting reaches 3.5%. Thus, salting meat and fish is not the best canning option. However, salting is indispensable in the preparation of herring and other salted fish products (delicacy, etc.), which are characterized by peculiar taste qualities. Here, the salting method is the best type of preservation.

Canning with sugar. When preserving with the use of sugar (jam, etc.), sugar concentrations of about 60% , which corresponds to at least 350 atm. osmotic pressure. This provides a fairly efficient bacteriostatic and bactericidal action in the preservation of berries and fruits. The preservative effect is enhanced by preliminary heat treatment (boiling jam), as well as by preliminary pasteurization (fruit and berry syrups).

To the preservative action of sugar, some yeasts and molds are very resistant, which are able to develop on media with a high concentration of sugar. These types of yeasts and molds are called osmophilic.

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