The Effect Of Postmortem Aging On Meat Quality And Volatile Compounds Of Meat Of Tibet Sheep

The indicator about aging mechanism which include pH, content of glycogen, myofibril fragmentation index (MFI) and activity of calpain(CAF) and meat quality which include shear force, rate of water loss, cooking loss, marbling score, chromaticity during aging of fifteen Tibet sheep from Sunan County was determinated, and multiple regression analysis between indicator about aging mechanism and meat quality during aging and step-wise regression analysis between initial indicator about aging and ultimate meat quality was carried out. While the volatile compounds of meat of Tibet sheep pre- and post- aging were also determinated. The result concludes as follows.1) There were significant variation about pH, content of glycogen, MFI and CAF during aging. The majority of variation of these indicators was completed before postmortem 72 h. After postmortem 24 h pH and content of glycogen varied insignificantly (P>0.05).2) The variation of MFI during postmortem 72 h account for 86.84% of total variation. There was significant positive relativity between pH and content of glycogen. While after postmortem 14 h there was significant positive relativity between CAF and MFI, loss of CAF connent closely with extent of cleavage of myofibril.3) Aging time has no effect on marbling score and has significant effect on shear force, rate of water loss, cooking loss. Compared with shear force, rate of water loss, cooking loss, the effect of aging time on chromaticity was less.4) Variation of CAF during postmortem 72 h(X₈), CAF at postmortem 0 h(X₆), variation of pH during postmortem 24 h(X₃), variation of content of glycogen during postmortem 24 h(X₁₀), MFI at postmortem 0 h(X₄) have good prediction on ultimate tenderness. The equation of step-wise regression analysis as follow: Y=2.272+1.238 X₃-0.013 X₄-0.613 X₆+1.959 X₈-0.326 X₉,R²=0.987.5) The rate of water loss and cooking loss was significantly influnced by pH. There was significant relativity between capacity of water holding and variation of pH during early aging.6) Chromaticity was significantly influnced by pH. Variation of pH during postmortem 24 h was primary factor in determining ultimate chromaticity7) Aging increased relative content of aliphatic sulfur compounds and furan thiol, but decreased relative content of thiazole. The effect of aging on sulfur compounds likely connect with decreasing pH during aging.8) Aging increase Strecker aldehyde, and products of lipid oxidation were also increased, such as hexanal heptanal, (E)2-octenal, (E)2-nonenal, 2,4-decdienal, 1-octen-3-ol, benzaldehyde, 1-penten-3-ol. Furthermore.9) Aging decreased p-cresol, phytan-2-ol, phytane which were derived from phytochemicals of diets.