In the case of electrolytes, which are due to dissociation decomposes into two or more ions, the va

Contents Introduction Osmoanabioza ratio microorganism of the water term water activity water content as the basis for the growth of microorganisms in food Combining control activities with other water conservation techniques, ore ida steak fries measurement and forecast values of water activity in food literature. Introduction
The influence of the water content in food to its perishability has been known since ancient times. Between 15,000 and 10000th BC, our ancestors began to keep a surplus of fish, meat and fruit drying in the wind and sun (Ray, 1992). Around 8000th BC introduced many innovations in the methods of preserving food. To ensure constant supplies of food, cereals and fruits were stabilized by natural drying and excess meat and fish are protected smoked and dry salting. Masson ore ida steak fries and Challet are 1795 applied artificial drying vegetables in preheated room. In the 20th century, innovations have included in artificial drying liquid application method of drying rollers and spray as well as freeze-drying. Methods of food preservation by drying ore ida steak fries and salting, developed over several millennia, were empirical and more as an art than a science. Quite interest in the influence ore ida steak fries of water activity (aw) on the quality and stability of food products began in the early 1950s (Scott, 1953 and 1957). It was caused by empirical and discordant observations ore ida steak fries between total moisture content and stability of the product. In contrast, the measured value of water activity (aw) is generally in good mutual relationship with the potential for growth and metabolic activity and has been adopted as a good indicator ore ida steak fries of the presence of water for microbial activity (Christian, 2000; Chirife, 1995; Lenovich, 1987). As a result of work in the last few years, control aw value is involved in various legal regulations, taking into account the activity of the water more than the total moisture content affects ore ida steak fries the growth, death, survival, sporulation and toxin production by different microorganisms and the adjusting the boundary aw value in food products. Of all the factors that affect microbial growth, death and survival in foods, aw influence on vegetative microorganisms and spores is one of those who are most studied by food microbiologists. . Osmoanabioza
Foodstuffs are often conserved procedures that aim to increase them in the osmotic pressure. The separation of the solvent and the solution of a substance permeable membrane occurs pursuit of balancing their concentration. When the membrane is not present, the concentration becomes equal due to diffusion phenomena. In the presence of the membrane also leads to equalization of the concentration by solvent (water) migrates from lower to higher concentrations of solids. The greater the difference in the concentration, ore ida steak fries the greater the driving force that pushes solvent molecules ore ida steak fries to pass through the membrane. If necessary to prevent the equalization of concentration, it would be necessary to apply some pressure ore ida steak fries in the middle koncentrovanijoj, which opposed the entry of solvent molecules and that pressure known as osmotic pressure and concentration equalization through permeable membrane is called osmosis. ore ida steak fries It is apparent that the osmotic ore ida steak fries pressure increases with decreasing water concentration. At the same time changing and some other characteristics: increasing boiling point, decreases the freezing point reduces the equilibrium relative humidity reduces the water activity etc.. The numerical value of the osmotic pressure is directly proportional to the concentration and absolute temperature. This value, in dilute solutions and only for nonconductors can be calculated from the equation:
In the case of electrolytes, which are due to dissociation decomposes into two or more ions, the value of the osmotic pressure is corrected Vant Hoffovim isotonic coefficient and. Water is one of the important conditions for the reproduction of microorganisms and their destructive activity. Knowing the effect of osmosis and micro-organisms need water, we can in a way that changing ore ida steak fries the substrate (food), making it unsuitable for microbial activity. In fact if we look at the cells of microorganisms in which the water with dissolved ore ida steak fries substances, ore ida steak fries it follows that in them, due to a concentration of soluble solids, the government determined osmotic pressure. In most cell microorganisms government osmotic pressure of from 0.3 to 0.6 MPa. If the surrounding environment (food) increase the concentration of dry matter, so that it is larger in comparison ore ida steak fries with the concentration ore ida steak fries in the cell micro-organisms, there will be a loss of water, or to plasmolisis cell microorganisms. Increasing the concentration of solids increases the osmotic pressure; on the principle of osmosis, the water in the cells of microorganisms ore ida steak fries (cell membrane permeable membrane =) enters the landscape higher concentrations of solids leading to dryness microorganisms. At a certain point the cells will inasmuch as it runs out of water that will disrupt normal life processes, will stop breeding - thus stopped and microbiological