Sunday, April 3, 2011
【 Weak current College 】 meat freezer storage technology knowledge 】
<br> Preservation of meat are all human beings since ancient times an important research subject, with the pace of change in modern lifestyle and traditional meat preservation technology can not meet people's needs, in-depth study of the preservation of meat preservation technology .imperative. .The preservation of meat and foreign scholars conducted extensive research. .At present the view that any kind of preservation measures have shortcomings, we must adopt an integrated preservation technology, the advantages of playing a variety of preservation methods, to complement each other, the effect is multiplied purposes. .Meat mainly by three factors of corruption; ⑴ microbial contamination, growth and reproduction; ⑵ lose fat oxidation; ⑶ myoglobin gas discoloration. .These three factors interact, the propagation of micro-organisms will promote fat oxidation and discoloration of myoglobin, and fat oxidation also change microbial strains and to promote the color of myoglobin, the author of the current methods of meat Preservation reviewed. .A traditional meat preservation technology <BR> 1.1 <BR> low temperature cold storage preservation is a widely used technical measures, in view of China's national conditions, the cold chain system is the most important means of meat preservation. .Is stored in the refrigerated meat slightly above the freezing temperature, usually between 2 ~ 4 ℃, the range of most of the pathogens to stop breeding, then the growth of psychrophilic spoilage bacteria can still be the recent discovery of a single nuclear proliferation Li Si line .Arthritis and intestinal bacteria Yersinia can also breed. .The growth of bacteria in the meat very fast, under the proper conditions, some bacteria only 20min or less time, in fact, under normal circumstances, so quickly fail to meet, because all of the environmental conditions meet .is not possible, bacterial growth depends on the length of bacteria, nutrients and temperature, PHvalue and water activity, low temperature preservation has the following disadvantages: (1) the process of freezing and thawing due to ice formation and salt precipitation efficiency Yi, so that .decrease the quality of meat; (2) of packing, surface water will sublimate and cause "cold burn" phenomenon; (3) high transportation costs when frozen Wei. .Preservation of low water activity <BR> 1.2 <BR> water activity is not the water content of all foods, but that microbes can use the water. .The propagation speed of micro-organisms and microbial species composition depends on water activity group (AW). .Most bacteria can only breed in the matrix of AW than 0.85, water activity requirements for botulinum 0.94 0.96 0.92 Salmonella, most bacteria was 0.90, Staphylococcus aureus was 0.87-0.88 when the water activity to 0.7 .or so, most of the microorganisms were inhibited Home RELSS reported that the surface of the meat inside and a detachable 45 Penicillium, at low water activity and higher temperatures, only to the growth of Aspergillus, the most common low-water .Active drying and preservation methods to add salt and sugar. .Other additives such as phosphate, starch and other meat can reduce the water activity. .<BR> 1.3 <BR> heat treatment heat treatment is present in meat to kill bacteria and pathogens of corruption, inhibit the enzyme activity can cause corruption of the preservation technology, heat treatment, although inhibition could play, destroy enzymes .role, and the heating can not prevent fat oxidation and myoglobin, but can promote the role of meat so the heat must be used in conjunction with other preservation methods. .<BR> 1.4 <BR> fermentation fermented meat products have good retention characteristics, it is the artificial environment control, the use of meat in the growth of lactic acid bacteria dominate the carbohydrates into lactic acid in meat products, reduce product .PH value, and inhibiting the growthof other microorganisms, fermented meat products can also be used in combination with other preservation techniques. .Preservation of modern technology <BR> 2 <BR> Although many of the traditional meat preservation technology is still in use, but new technology has developed rapidly Preservation, Preservation of modern meat technology, including joint will rot preservatives, vacuum packaging, gas .preservation technology transfer and radiation preservation technology 4. .<BR> <BR> 2.1 Preservation and preservation of the meat into 4 categories of food additives: preservatives, antioxidants, hair color agent and quality improver. .Preservatives are divided into chemical preservatives and natural preservatives. .Preservative often used in combination with other preservation techniques. .<BR> 2.1.1 Chemical preservatives, chemical preservatives <BR> main organic acids and their salts. .Organic acids used in meat preservation, including acetic acid, formic acid, citric acid, lactic acid and its sodium salt, anti-cyclic blood acid, sorbic acid and potassium, phosphate and so on. .Many trials have demonstrated that these acids alone or in combination, to extend the shelf life of meat has a certain effect, which is the most used acid, sorbic acid and its salts, sodium lactate. .<BR> (1) starting from 1.5% acetic acid had significant inhibitory effects within 3%, acetic acid does not affect the color of the meat. .Because in this concentration, the inhibitory effect of acetic acid, slowing the growth of microorganisms, to avoid mildew caused by flesh-colored dark green, when the concentration exceeds 3%, have an adverse effect on the flesh, which is the acid itself .result, foreign study showed that 0.6% of acetic acid with 0.046% formic acid mixture impregnated meat 10S, not only greatly reduced the number of bacteria, and can maintain its flavor and almost no effect on the color, such as a single treatment with 3% acetic acid, .can be inhibitory, but the color of the harmful effects of ascorbic acid with 3% acetic acid +3 processing. .Protect the color due to ascorbic acid, meat color can be maintained well. .ANDERSON (1983) on the carcass first with 40 ℃ hot water spray, and then 3% acetic acid treatment, can reduce the bacterial content of 96.8%. .DRtAoed (1983) with 2% lactic acid +1% +0.1% +0.25% citric acid aqueous solution of ascorbic acid spray carcass can prolong the shelf life (2) has very limited use of sodium lactate. .USDA that sodium lactate is safe, maximum use of up to 4%, sodium lactate, the mechanism of corrosion of two, the addition of sodium lactate can reduce product water activity, thereby preventing the growth of microorganisms; lactate ion has antibacterial functional groups. .Sodium lactate on rat damage, Salmonella and Staphylococcus aureus are inhibited, at present, lactate is mainly used in corrosion from the inside, <BR> (3) potassium sorbate in meat products is widely used, a false charge to be that antibacterial .It can and sulfur-based microbial enzyme systems integration, thus undermining a number of important enzymes seconds, to inhibit microbial proliferation and preservation purposes, potassium sorbate preservative in meat can be used alone, but also, and phosphate, acetic acid combined with .effect. .<BR> (4) phosphate as a quality improver Preservation play its role in the phosphates in the same products have the following effect: markedly improved water retention of meat products; use of its products, plus cooperation with the slow oxidative rancidity, and enhance preservative .antibacterial effect, since the provisions of the 1982 U.S. Department of Agriculture in meat products can be added after the 0.5% phosphate, phosphate in the meat industry has become an indispensable additive. .<BR> 2.1.2 Natural Preservatives <BR> natural preservatives on the one hand, health guarantee, on the other hand to better meet the needs of the consumer, at present, domestic and international research in this area is very active, natural preservative .the future development trend of preservatives. . (1) Tea Antioxidant deterioration in performance. .Preservation of tea polyphenols on meat to play a role in three ways; lipid oxidation; antibacterial; addition to odor substances. . (2) spice extracts, many spices contain bactericidal, antibacterial ingredients, extracted as a preservative, safe and effective. .Garlic Allicin and allicin garlic, nutmeg essential oil contained in nutmeg, cinnamon and clove essential oil in the clove oil, etc., all have good antibacterial, anti-bacterial effect. . (3) Nisin (Nisin) application of Nisin is a new type of meat preservation technology, Nisin is synthesized by certain lactic acid streptococci a peptide antibiotic. .It can only crucify Gram-positive bacteria, yeast, mold, and gram-negative bacteria had no effect. .Nisin is a narrow spectrum antibacterial agent. .Nisin can prevent Clostridium botulinum spore Bacillus effective, these bacteria produce endospores is a major food spoilage microorganisms. .Currently, the use of Nisin in the form of two types of lactic acid bacteria in vivo inoculation into the food; the other is the separation of its metabolites Nisin be used. .In addition, trehalose, mannan, chitosan, lysozyme and other natural preservatives are being studied. .<BR> 2.2 <BR> vacuum packaging vacuum packaging technology is widely used in food preservation technology, China will use vacuum-packed meat products, increasing the role of vacuum-packed 4 main areas: (1) inhibition of microbial growth: Anti- .secondary pollution; (2) slow the rate of fat oxidation, (3) the meat clean, enhance competitiveness, vacuum-packed in three forms, the first is to organize a good meat into the packaging bag, removing the air, and then .vacuum packaging, and then blowing hot air, so heat shrink material, close to the meat surface, the second method is rolling thermoformed packaging, the third method is vacuum tight packing, this method widely used in Europe. .<BR> 2.3 modified atmosphere packaging technology, also known as ventilation <BR> packaging modified atmosphere packaging technology is placed in a sealed standard food, deprived of air, with a good choice of gas to the gas atmosphere packaging in order to inhibit microbial .growth, thus prolonging the shelf life of food. .<BR> <BR> Gas commonly used in modified atmosphere packaging, there are three: <BR> (1) CO2 inhibited the growth of bacteria and fungi, especially in the early bacteria can also inhibit the enzyme activity, and 25% at low concentration .inhibitory effect is better, and has a water-soluble. .<BR> (2) the role of oxygen is to maintain oxymyoglobin, the flesh colored, and can inhibit the anaerobic bacteria, many of the harmful bacteria but also for creating a good environment, <BR> (3) Nitrogen is an inert .filled with gas, nitrogen does not affect meat color, to prevent oxidative rancidity, mold growth and parasites harm. .<BR> In meat preservation, carbon dioxide and nitrogen are the two main gases, there is a certain amount of oxygen to help extend the shelf life of meat, therefore, must choose the appropriate blending ratios for modified atmosphere packaging of fresh meat in Europe .gas ratio of oxygen: carbon dioxide: nitrogen = 70:20:10 or oxygen: carbon dioxide = 75:25. .Currently the most effective international meat preservation technology is a high carbon dioxide CAP inflatable packaging systems. .<BR> 2.4 <BR> meat preservation technology of radiation Radiation Preservation of meat than 40 years. .Radiation technology is the use of atomic energy-ray radiation for sterilization. .Now that the method of radiation exposure with the safety of food. .Joint Committee on Food Irradiation (EDFI) proposed that all the major categories of food are available all kinds of rad or less one hundred million doses of radiation, this dose does not cause toxicological hazard. .1988, Hefei, China University of Technology and Commercial Bureau to study the second of the "radiation preservation of fresh meat", the results are satisfactory, at room temperature 25 ℃, preserved pork, its color, smell, taste and meat similar..