The main reasons for meat spoilage are the reproduction of microorganisms, the action of enzymes and oxidation. In theory, meat storage is slaughtered and processed, using good hygiene practices to prevent microbial contamination as much as possible. Use appropriate preservation and preservation methods to prevent or delay the process of these effects.
Packaging technology is widely used in the preservation of fresh meat. The main functions of packaging are: inhibiting the growth of microorganisms; preventing secondary pollution; slowing down the speed of fat oxidation; making meat products neat and improving competitiveness.
1. Vacuum Bag Packaging (VP). Vacuum Bag Packaging reduces oxygen levels by drawing out the air inside the package. The lavender can keep the myoglobin in the reduced state of the meat, but when the meat is taken out of the bag, it can quickly restore the bright red color; the contact between the yin and the meat and the outside world causes pollution, so that the product and the outside world are guaranteed. The high negative diaphragm prevents weight loss due to dehydration of the meat surface; inhibits the growth and reproduction of aerobic bacteria and relatively prolongs the shelf life of the meat.
There are three kinds of domestic fresh meat packaging, with a shelf life of up to 21 days;
(1) The cut beef and pork pieces are packed in a Shrink Bag, then vacuum heat sealed, and the bags are shrinked with hot water;
(2) Thermoforming vacuum Packaging machines and high-barrier Thermoforming Film packaging. Place a piece of beef or pork in a thermoformed plastic box and vacuum seal with mulch.
(3) Vacuum Skin Packaging VSP Trays is widely used in Europe. At present, domestic researches have been carried out to combine vacuum packaging with brighteners. Take full advantage of their advantages and have a good preservation effect.
2. modified atmosphere packaging (MAP or CAP). Modified atmosphere packaging is to put fresh meat into the package, remove the air, and replace the gas environment in the package with the selected atmosphere to inhibit the growth of microorganisms, thereby prolonging the shelf life of fresh meat. The gases commonly used in modified atmosphere packaging are: (1) CO2 growth of bacteria and fungi, especially in the early stage of bacterial growth, can also inhibit the activity of enzymes and molds, while bacteria and Achromobacter are resistant to carbon dioxide. When inhibited, CO2 has almost no inhibitory effect on yeast and no inhibitory effect on lactic acid bacteria until anaerobic bacteria. Studies have shown that the use of 100% CO2 modified atmosphere packaging of lamb can significantly prolong the storage period and significantly inhibit Pseudomonas and lactic acid bacteria. (2) The role of CO2 is to maintain oxymyoglobin and make the flesh bright, but it also creates a good environment for many harmful bacteria; (3) N2 is an inert filling surface gas, which does not emit flesh color, which can prevent oxidative rancidity, Mold growth, parasites prevent the collapse of the package due to the large amount of CO2 dissolved in the meat.
In meat preservation, the proportion of the world's mixed air is not the same. The preservation effect is different, usually divided into high oxygen packaging and low oxygen packaging. Nitrox toned packaging can maintain a good red color. In high oxygen-modified packaging, when the CO2 concentration is lower than 20%, the growth of aerobic bacteria is slow. When the CO2 concentration exceeds 20%, the bacteria can be halved. But when the CO2 concentration is higher than 25%, the water-soluble protein precipitates, which makes the meat have a comprehensive color. Therefore, the CO2 concentration in the hyperoxic adjustment package is generally between 20% and 25%, and the O2 concentration is greater than 60%. For N2; the purpose of low-oxygen modified packaging is to inhibit CO2, but it cannot maintain the color of flat meat. The mixed gas range of low-oxygen modified packaging is relatively wide, CO2 is in the range of 50%-90%, and N2 is in the range of 10% to 40%. In the range of %, the proportion of O2 is between 1% and 10%. Small retail packaging adopts high-oxygen-modified packaging, and large-scale fresh meat packaging adopts low-oxygen packaging. Store pork in air, vacuum and modified atmosphere under cooling conditions at 0°C-4°C. The results show that: O220%, CO230%, O250%, CO250% modified pork packaging has better preservation effect than vacuum packaging. The packaging and air packing are good and the shelf life can be extended by 6 days.
Studies have shown that the addition of CO to modified atmosphere packaging utilizes CO and myoglobin to form carbon monoxide myoglobin (MbCO), which is more stable than oxymyoglobin (MbO2), while giving the meat a bright red color after cooling. Foreign studies have shown that the fresh-keeping effect of modified atmosphere packaging with 1% CO is better than that of high-air packaging such as vacuum, and does not contain CO. Domestic experts have conducted research on cold meat in different packaging forms. The experimental results show that the CO-containing group is an ideal method for fresh meat preservation. During the 21-day storage process, not only TVB and TBA values were low. , red and stable, no peculiar smell, can inhibit the growth of spoilage bacteria, in addition to the weak inhibition of lactic acid bacteria, has a strong inhibitory effect on Pseudomonas, Chlamydia and Clostridium thermophilus, and has a significant effect on spoilage bacteria Better than vacuum packing group and oxygen-containing packing group.
As cold meat becomes the mainstream of meat consumption, the packaging and sales of cold meat is an imperative trend. Reasonable and effective packaging will be more and more widely used in the production and distribution of cold meat. developing.
