Heterocyclic amines in aged and thermally treated pork longissimus dorsi muscle of normal and PSE quality

Abstract Here we have studied the effects of ageing time (as non-aged, 24 h post mortem vs. aged, 3, 6 and 10 days post mortem , kept at 2 °C), muscle quality (normal vs. pale, soft and exudative [PSE]) and internal cooking temperature ( T i , 70 and 95 °C) on the content of HAs in grilled steaks. HA precursors (creatine, creatinine, free amino acids, monosaccharides), ageing, and the muscle quality indicators of drip loss, instrumentally measured colour, pH, non-protein nitrogen, and grilled-meat WBSF of the pork longissimus dorsi muscle were determined. In general, all of the ageing and muscle quality indicators and precursors of the HAs were influenced by ageing time. Creatine content decreased significantly, and creatinine increased with days of ageing, dependent on muscle quality. There was higher content of total free amino acids after 10 days of storage, as compared to non-aged pork. A higher level of free amino acids was seen in normal as compared to PSE pork muscle. The glucose content increased with ageing, and there was a higher glucose content in PSE as compared to normal muscle. Five specific HAs were measured: PhIP, MeIQx, DiMeIQx, Harman and Norharman. The total HA content increased with ageing (non-aged and normal pork HA content, 1.35 ng g −1 ; after 3 days, 1.38 ng g −1 ; after 6 days, 1.77 ng g −1 ; and after 10 days, 3.49 ng g −1 ) and it was dependent on the internal temperature; greater amounts of HAs were formed in samples grilled to T i  = 95 °C, than in samples grilled to T i  = 70 °C (8.34 vs. 2.36 ng g −1 ). No marked differences due to muscle quality were seen in HA content at T i  = 70 °C (with the exception of MeIQx). The mean HA content of PSE samples grilled to T i  = 95 °C was 22% more than for the normal samples.