Freezing is anabiotički preservation method, which means that it is not the goal of freezing to des

Contents INTRODUCTION PRINCIPLES OF FREEZING Speed freezing olive harvesting machine Factors affecting the quality olive harvesting machine of frozen fruit Selection of appropriate products for freezing preparation, pre-treatment and packaging olive harvesting machine Preparation Pre-Treatment Packages Factors affecting the quality of frozen fruits Effects of freezing, storage olive harvesting machine in the freezer and thaw the fruit tissue: olive harvesting machine physical , chemical and biochemical changes of the cell plants physical changes and quality of chemical and biochemical olive harvesting machine changes and quality stability Thawing frozen fruits Microbiological quality and safety of frozen olive harvesting machine fruit Legislation METHOD olive harvesting machine OF FREEZING future development of conclusions. INTRODUCTION
Freezing is anabiotički preservation method, which means that it is not the goal of freezing to destroy microorganisms, but also to create olive harvesting machine conditions that prevent their activity. Food is preserved until the temperature is low, when the food thaws, microbes olive harvesting machine are again activated.
This paper describes the main principles of production and processing of frozen fruit (inspection of raw materials, pre-processing, packaging, freezing process and keep refrigerated) and are presented modern olive harvesting machine ways of preservation of sensory and nutritional quality of care and frozen olive harvesting machine fruit. . PRINCIPLES OF FROST
The process reduces the freezing temperature of the food until its thermal center (venue with a maximum temperature at the end of the freezing process) olive harvesting machine is reached at -18 C, and accompanying crystallization of water, the main component of plant tissue. The water in fruits and fruit products occupies 85-90% of their entire composition. From the physical point of view, vegetable and animal tissue can be considered dilute solution of water, which is a natural medium where occurring chemical and biological cellular responses and develop microorganisms. Crystallization of water during freezing reduces the water activity (aw) in these tissues, and as a consequence, olive harvesting machine reduction of chemical and biochemical reactions and microbial growth. Freezing also includes the use of low temperatures resulting in slower reaction as the temperature is lowered. The study of temperature changes during freezing is the basis for understanding the changes in the product that occur during the process of freezing. Figure 1 shows a typical curve of freezing at different temperature levels. After the product was cooled to 0 C, produces ice (see part A, Figure 1). The exact temperature at which ice crystals form the first depends on the type of product and is the consequence of concentrating substances independently of the water content. For example, fruits with high water content ( 90%) has a freezing point below -2 C or -3 C, until the meat with a lower water content ( 70%) has a freezing point of -1 C; The main difference is the high concentration of sugars and organic acids in fruit. Icing occurs olive harvesting machine after the product reaches a temperature below freezing (-5 C to -9 C) for a few seconds. This process is known as a super-cooling (point S in Figure 1).
Subsequently, the partial release of heat during the formation of the first ice, the temperature increases until it reaches the freezing point (point B in Figure 1). Part BC in Figure olive harvesting machine 1 corresponds to freezing of most of the water in the tissue at a temperature which is practically constant, negative drop of the freezing point due to concentrating the solution. The increase in the concentration of the solution, as it comes to freezing, implies that not frozen part passes the physical changes olive harvesting machine in terms of ionic values, pH and viscosity. This increases the risk of enzymatic and chemical reactions, ie. enzymatic browning and oxidation-reduction activity reaction, with bad effects on the quality of frozen fruit. The shorter the BC part of quality olive harvesting machine frozen fruit is larger. This means that fast freezing olive harvesting machine produces a better quality of frozen fruit (see curves b and c in Figure 1). Part CD corresponds cooling products to storage temperature with a significant olive harvesting machine increase in the concentration of the solution olive harvesting machine in a non-frozen part. Below -40 C, newly formed ice may not be noticed. Up to 10% of water can be not frozen. olive harvesting machine This water is connected with the macromolecular structures of proteins or polysaccharides that participate in physical and biochemical reactions. In the frozen food frozen relationship between water and the rest of the solution depends on temperature and concentration of the solution (Hui 2006).
The presence of ice and increasing olive harvesting machine solution concentration olive harvesting machine has a significant effect on the reaction and the state matrix of fruit. The concentration of the solution increases as freezing progresses; and therefore the solution of the matrix can nesmrznutog iscureti the cell structure, resulting in a loss of turgor (pressure in plants) and internal damage. Damage stimulated solution can occur whether it is fast or slow freezing. To prevent damage to cells aqueous solutions are usually added cryoprotectants, such as sugars (Hui, 2006). olive harvesting machine . Freezing rate
Controlling the speed of freezing is an important aspect of reducing damage to cells, which causes a loss of quality olive harvesting machine in frozen fruits. There are three types of cell damage due to frost: Damage stimulated solution, osmotic damage