Study On The Effect Of Oxygen Permeability Of Plastic Packaging Materials To The Color And Freshness Of Pork

The pork has been the most important meat to Chinese consumers, and our country will consume large quantity of pork every year. In our country, the majority of the pork is still used by the consumers directly in the way of raw meat for our meat processing technology is not mature yet and the consumption percentage of the meat products is only 5% of the total meat consumption. However, most of the domestic hogs are slaughtered in the irregular slaughterhouse or by individuals and backward in equipments, substandard in technology, serious pollution of microorganism and being sold best without being packed, and all of these easily result in the second-time pollution. And then, the duration of the products will be short which causes huge economic loss and there is big hidden danger which directly threaten to people's health. To pork the pork is one of the efficient steps to improve its quality, and its main purpose is to avoid the second-time pollution, deterioration and prolong the duration. With the increase of the demand of the market, the profound study to the packaging of pork becomes urgent and very important.The chief material of packaging raw and fresh meat is plastic. Plastic is a kind of high polymer------resin as the basic element, and being added different addictives to improve the functions.Plastic is mostly used as packaging material in the way of film and because the plastic film can be penetrated by gas, and after being packed, if there exists the gradient of gas component, the gas will penetrate from high component to low component. During the circulation, because there exists the pressure difference of O₂, CO₂. N₂ in and out the package, the inside fresh meat will have the exchange of the gas inside and outside, and among them, the exchange of O₂ will cause the change of the density of O₂ which can speed up the propagation of aerobic bacteria, the change of the colour of myoglobin and oxymyoglobin and the burning of fat, and then make the duration of freshness of raw pork shortened.The way of the article is to use the fresh pork as the material, and the four packaging ways: vacuum-packaging, common packaging, modified atmosphere packaging (MAP 80%O₂,20%CO₂), modified atmosphere packaging (MAP 50% O₂, 50% CO₂). Every packaging way is carried by using the plastic packaging material with different oxygen permeability, color difference meter, microbiology and physical chemistry testing way to analyse and test the change of colour, total quantity of bacteria, TVB-N, pH, odor, the possibility of acceptance and viscosity etc.The purpose of the study is to analyse the influence of different plastic packaging materials to the colour and freshness of pork under the situation of different packaging ways and oxygen permeability. The results are as follows:1. About the four materials: high barrier material (oxygen transmission rate(OTR) : 18. 539× 10 ⁶ cm³/m²Â·d·pa), good barrier material(OTR: 328. 55 × 10 ⁶ cm³/m²Â·d·pa), mid-barrier material (OTR: 625. 29×10 ⁶ cm³/m²Â·d·pa), low barrier material(OTR: 4234. 8× 10 ⁶ cm³/m²Â·d·pa).Through testing the change of the quality of the vacuum-packed pork, the result is: after being preserved for two days, the low barrier material color of the High barrier material packaged pork became dull red and pH increased; the fourth day, the number of bacteria exceeded; the sixth day, the odor, the possibility of acceptance and viscosity became worse. During the preservation, the color of the good barrier material packaged pork is good and the number of bacteria exceeded and the possibility of acceptance and viscosity became worse till the eighth day. The color of the mid barrier material packaged pork can be kept good in four days, and the number of bacteriaexceeded and the possibility of acceptance and viscosity became worse till the sixth day. Although to low barrier material packaged pork, the number of bacteria exceeded and the possibility of acceptance and viscosity became worse till the sixth day, the color became light obviously.Comprehensively compare, under the situation of vacuum-packaging, high barrier material has the best effect to the color and keeping pork fresh, and good barrier material, good barrier material, low barrier material are inferior to it in turn.2. Through testing the change of the quality of the commonly packed pork under the situation of being packaged with packaging materials with different barrier efficency, the result is: after being preserved for two days, the color of the high barrier material packaged pork became dull red and pH increased; the fourth day, the number of bacteria exceeded; the sixth day, the odor, the possibility of acceptance and viscosity became worse. The good barrier material packaged pork has the same result. The color of the mid barrier material packaged pork can be kept good in the duration of preserving, and the number of bacteria exceeded till the fourth day and the possibility of acceptance and viscosity became worse till the sixth day. after being preserved for two days, the color of the low barrier material packaged pork became light obviously, and the number of bacteria exceeded till the fourth day and the possibility of acceptance and viscosity became worse till the sixth day.Comprehensively compare, under the situation of common-packaging, mid barrier material has better effect of keeping color and fresh and the others have inferior effect.3. Through testing the change of the quality of MAP(80% O2, 20% CO2)pork under the situation of being packaged with packaging materials with different barrier efficency, the result is: after being preserved for four days, the color of the high barrier material packaged pork became yellow and the number of bacteria exceeded till the sixth day and the possibility of acceptance and viscosity became worse till the eighth day. The color of the good barrier material packaged pork can be kept good in the duration of preserving; the number of bacteria exceeded and the possibility of acceptance and viscosity became worse till the eighth day. Although pH increased, it is still in the scope of the first-class freshness. The color of the mid barrier material packaged pork became light red, and bright yellow in the second day. The number of bacteria exceeded and the possibility of acceptance became worse till the sixth day and viscosity became worse till the eighth day. The color of the low barrier material packaged pork became light obviously in the second day. The number of bacteria exceeded in the sixth day and the possibility of acceptance and viscosity became worse in the eighth day.Comprehensively compare, been MAP(80% O2, 20% CO2) packaged, good barrier material has best effect of keeping color and fresh, and high barrier material, mid barrier material, low barrier material are inferior to it in turn.4. Through testing the change of the quality of MAP(50% O2,50% CO2)pork under the situation of being packaged with packaging materials with different barrier efficency, the result is: the color of the high barrier material packaged pork can keep good within 10 days; the number of bacteria exceeded and the possibility of acceptance and viscosity became worse till the tenth day. The color of the good barrier material packaged pork can be kept good in the duration of preserving; the number of bacteria exceeded and the possibility of acceptance and viscosity became worse till the eighth day. Although pH increased, it is still in the scope of the first-class freshness. The color of the mid barrier material packaged pork can keep good within 10 days; the number of bacteria exceeded and the possibility of acceptance and viscosity became worse till the eighth day. The color of the low barrier material packaged pork can keep good within 8 days; the number of bacteria exceeded and...