Preservation and packaging technology of the hotte

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Editor's note: in many parts of China, chilled meat is also known as "assured meat", and China is vigorously promoting the "assured meat" project Some experts assert that half chilled meat has become the mainstream of China's meat consumption in the new century

developed countries have been producing and promoting raw meat since the 1920s and 1930s. At present, more than 90% of the raw meat consumed is chilled meat. Although the cold chain in China has tended to be perfect and standardized at present, chilled meat can not completely inhibit the growth and reproduction of some psychrophilic microorganisms in the range of 0 ℃ ~ 4 ℃ used for cold storage. Therefore, the shelf life of chilled meat is short, and the surface browning and juice loss are serious. The storage period is generally 3-7 days, which cannot fully meet the needs of market circulation. In addition, China's traditional consumption habits have affected the promotion of chilled meat in China. Prolonging the shelf life of chilled meat is very important for the development of chilled meat. As a result, there is a trend of "fresh meat packaging: spreading from the west to the East". (see the special content of the information center of this website for details)

therefore, how to extend the fresh-keeping period of chilled meat is the key to the development of chilled meat. For this reason, food experts at home and abroad have carried out a lot of scientific research, and many new meat preservation technologies such as preservative preservation, radiation preservation, low water activity preservation and other research results have been published frequently. The new packaging technology is also crucial to prolong the fresh-keeping effect of chilled meat

choosing appropriate packaging materials and packaging technology can play a very significant role in prolonging the fresh-keeping period of chilled meat and ensuring the hygiene and quality of meat. Then, this topic will also briefly discuss the preservation and packaging technology of chilled meat for reference

★ what is chilled meat

chilled meat, also known as cold fresh meat and assured meat, refers to fresh meat that is slaughtered in strict accordance with the requirements of the quarantine and inspection system, which is rapidly cooled and reduced to 0 ℃ - 4 ℃ within 24 hours, and is always maintained in the range of 0 ℃ - 4 ℃ in the subsequent processing, circulation and sales process

it refers to the fresh meat that quickly cools the carcass of livestock and poultry slaughtered after strict implementation of the quarantine system, so that the carcass temperature (the rear leg is the measuring point) is reduced to 0 ℃ - 4 ℃ within 24 hours, and remains within the range of 0 ℃ - 4 ℃ in the subsequent processing, circulation and retail process. Because the chilled meat is always under cooling conditions and has experienced a full post ripening process, compared with hot fresh meat and frozen meat, the chilled meat has the characteristics of less juice loss, soft and elastic texture, delicious taste and high nutritional value, so it is widely welcomed by consumers

★ packaging materials suitable for chilled meat

chilled meat, regardless of the thermal insulation material, should have good dimensional stability. What kind of packaging should be selected, has a common feature, that is, the material should be highly barrier, so as to prevent the invasion of external air and bacteria, internal water dispersion loss, etc., so as to improve the hygiene and safety of meat products. The materials selected for these packages are the key to whether the packaging effect is obvious or not. The following mainly introduces the widely used PVDC high barrier materials

pvdc is a kind of excellent food packaging material, which makes the material show low gloss and flocking like effect. In particular, it is resistant to high temperature cooking and has good barrier to oxygen, steam and various odors, which is unmatched by other plastics

the PVDC plastic used in the packaging of chilled meat is not a simple PVDC film, but a multi-layer coextrusion film with PVDC as the barrier layer. The copolymer of vinylidene chloride and methyl acrylate, methacrylic acid, acrylonitrile is selected as the barrier layer, and is made by coextrusion with other wear-resistant materials, heat sealing materials, etc. This film has extremely high oxygen resistance. 40 enterprises were ordered to rectify the gas barrier within a time limit, and the oxygen transmission rate was 2 · ATM · 24h · 23 ℃ · 65% RH; Extremely high water vapor barrier, water vapor transmission rate 2 · ATM · 24h · 23 ℃ · 90% RH. At present, the more common structures in the world are PE/tie/PVDC/tie/PE and PE/tie/PA/tie/PVDC/tie/PE five or seven layer structures. Multi layer coextrusion high barrier film used in modified atmosphere packaging technology is mainly made by tape casting and film blowing, which does not have shrinkage, and the thickness is generally 90 μ m~150 μ m. With high transparency and puncture resistance, it can inhibit microbial reproduction by changing the gas environment inside the package. Vacuum shrinkable packaging is mainly made of multi-layer coextrusion double bubble blowing film. PVDC is used as barrier layer. After coextrusion with other special materials by double bubble method and off-line treatment, the product shrinkage is about 35% - 45%. Using the heat shrinkability of the shrink film to make it close to the surface of meat products, it can prevent moisture seepage, and the thickness is generally 50 μ m~90 μ m。

Application of PVDC in chilled meat packaging

★ fresh keeping packaging of chilled meat

the main reasons for meat spoilage are microbial reproduction, enzyme action and oxidation. In theory, the storage and preservation of meat is to adopt good hygienic operation norms in slaughtering and processing to prevent microbial pollution as much as possible. Appropriate packaging and preservation methods should be adopted to eliminate or delay the process of these effects

packaging technology is widely used in fresh meat preservation. The main functions of packaging are: inhibiting microbial growth and preventing secondary pollution; Slow down the speed of fat oxidation; Make meat products tidy and improve competitiveness

I. vacuum packaging (VP). Vacuum packaging reduces the oxygen content by pumping out the air in the package, and keeps the myoglobin in the meat in the reduced Lavender state, but when the meat is taken out of the bag and exposed to oxygen, it can quickly return to bright red; Prevent the contamination caused by the contact between meat and the outside world, and ensure the hygiene of products; The high barrier membrane prevents the weight loss caused by dehydration on the meat surface; Inhibiting the growth and reproduction of aerobic bacteria has relatively prolonged the shelf life of meat. There are three forms of vacuum packaging for fresh meat abroad, with a shelf life of up to 21 days: (1) the segmented beef and pork pieces are packed in shrink film bags, then vacuumized and heat sealed, and then hot water is used to shrink the bags; (2) It is packed with thermoforming vacuum packaging machine and high barrier plastic film. Put a single piece of beef or pork into a thermoformed plastic box, and then cover it with a film to vacuum and heat seal; (3) Vacuum body fitted packaging has been widely used in Europe. At present, there are domestic research on the combination of vacuum packaging and preservative, so that they can give full play to their respective advantages and have good fresh-keeping effect

II. Modified atmosphere packaging (map or cap). Modified atmosphere packaging is to put fresh meat in the package, remove the air, and replace the gas environment in the package with the selected gas, so as to inhibit the growth of microorganisms and prolong the shelf life of fresh meat. The commonly used gases in modified atmosphere packaging are: (1) CO2 inhibits the growth of bacteria and fungi, especially in the early stage of bacterial reproduction, and can also inhibit the activity of enzymes. Aerobic bacteria such as mold, trichomonas aeruginosa and Achromobacter are highly sensitive to CO2 and are inhibited. CO2 has little inhibitory effect on yeast and no inhibitory effect on anaerobic bacteria such as lactic acid bacteria. Studies have shown that lamb packaged with 100% CO2 modified atmosphere can significantly prolong the storage period, significantly inhibit Pseudomonas, and lactic acid bacteria become the dominant bacteria. (2) The function of CO2 is to maintain oxygenated myoglobin, make the meat colorful, and inhibit the growth of anaerobic bacteria, but also create a good environment for many harmful bacteria; (3) N2 is an inert filling gas, which does not affect the color of meat, can prevent oxidative rancidity, mold growth and parasitic pests, and prevent package collapse caused by a large amount of CO2 dissolved in meat

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