LPT 321: Meat Science (1+1)

pH

• pH refers to the negative logarithm of hydrogen ion concentration.
• The pH of fresh meat, more precisely muscle at 45 minutes post slaughter is in the range of 6.8 -7.2, which reduces to about 5.2-5.6, at about 24 hours post slaughter in case of cattle, while it takes in about 4-8 hours in pigs
• This decline in pH is on account of the conversion of the glycogen stored in the muscle to lactic acid.
• In case of pigs, stress in the form of rough ante-mortem or peri-slaughter handling, high environmental temperature, fighting etc., results in the coming down of pH to pHu values within an hour of slaughter, when the carcass is still warm(35 ⁰ C).
• This combination of high temperature and low pH results in changes in properties of the muscle proteins (protein denaturation) resulting in them being less capable of retaining water in the inter-myofibrillar spaces, and hence becomes soft and exudative. The loose network of muscle proteins allows more light to be absorbed hence pale in colour.
• In case of cattle, stress in the form of rough ante-mortem or peri-slaughter handling, resulting in physical exhaustion results in the depletion of glycogen and the ph does not come down and remains at above 6 even 48 hours after slaughter .
• This high pH results in the muscle protein lattice remaining undisturbed and hence appears dark in colour and firm in texture and dry on the external surfaces.