Relationship Between Water Distribution, Antioxidation And Water-Holding Capacity In Fresh Pork Meat

Pork production of China has been the first place in the world,but in pursuit of pork production,all kinds of rapid culture method(growth promoting additive) led to a sharp decrease of pork meat quality, especially for the water-holding capacity(WHC) of fresh pork meat.The decline of WHC not only affects the sensory and edible quality of pork meat,but also seriously reduces the economic value of pork meat.So it is very important to study the WHC mechanism and to find a way to control drop loss of pork postmortem.Low Field-Nuclear Magnetic Resonance (LF-NMR) can test the transverse relaxation time(T₂) of pork.These tests can get much important information of water mobility and distribution in pork meat,and provide evidence of changing of WHC in postmortem pork meat.This paper investigated water distribution,antioxidation and WHC of fresh pork(Jinhua pigs in the original area of Zhejiang,China,JH and hybrid pigs of Duroc×Landrace×Yorkshire).The results were as fellows:1.Research on water distribution of fresh pork using LF-NMRLF-NMR can accurately distinguish the different activity water of pork,exudation of pork and water by T₂.Testing the T₂ of pork by LF-NMR we found there were three different T₂ section in pork which respectively represented T₂₁(bound water),T₂₂(immobilized water), T₂₃(free water).We investigated the different weight and different drying degree of the pork sample by LF-NMR.The results show that T₂ integral area could accurately reflect the change of the water content in pork.The result of water distribution in postmortem Jinhua pigs and DLY was as follow:T₂ integral area of Jinhua pig was higher than DLY.The T₂₂ integral area of two breeds declined postmortem.T₂₂ integral area of Jinhua pig declined faster than DLY in 0～6h postmortem.The finishing weight of DLY had a great effect on T₂ integral area,T₂ integral area of 75kg DLY was significantly higher than 90kg and 105kg DLY.2.Research on antioxidation and meat quality of fresh porkDrop loss of DLY was higher than Jinhua pig.The drop loss of DLY at 24h,48h,72h,was higher than Jinhua pig 38.5%,48.1%,32% respectively.The pH value of DLY at 0～72h was lower than Jinhua pig. The pH value of two breeds of pig declined sharply at 0～6h.The free fatty acid of DLY was significantly lower than Jinhua pig.The result of antioxidation revealed antioxidation of Jinhua pig was significantly higher than DLY.The evidence was as follows:The glutathione peroxidase(GSH-PX) activity of Jinhua pig was 2～3 times higher than DLY.The total antioxidant capacity(T-AOC) of Jinhua pig was 3～5 times higher than DLY.The malondialdehyde content in Jinhua pig was lower than DLY.The time when the malondialdehyde content increased to the highest point in Jinhua pig was later 12h than DLY.A high,significant correlation was found between the T₂₂ integral area constant and the malondialdehyde content(r＞0.6).The malondialdehyde content increased in fresh pork postmortem,which indicated the deterioration of the integrity of cell membrane.The intracellular water crossed the cell membrane to the extracellular,which led to a increase of the content of extracellular water.This process may cause the water-holding capacity of fresh pork decrease postmortem.