Influence of sodium pyrophosphate on thermal inactivation of Listeria monocytogenes in pork slurry and ground pork

The thermal inactivation (55-62.5 degreesC) of Listeria monocytogenes in po rk slurry and ground pork that contained 0, 0.25 or 0.5% sodium pyrophospha te (SPP) was evaluated Surviving cells were enumerated on Modified Oxford M edium. Decimal reduction (D)-values in pork slurry control (0% SPP) were 8. 15, 2.57 0.99, and 0.18min, at 55 57.5, 60 and 62.5 degreesC, respectively; D-values in ground pork ranged from 15.72min at 55 degreesC to 0.83 min at 62.5 degreesC. D-values in pork slurry that contained 0.25% SPP (w/v) were 4.75, 1.72, and 0.4 min, at 55, 57.5, and 60 degreesC respectively; the va lues in ground pork ranged from 16.97 at 55 degreesC to 0.80 min at 62.5 de greesC. At 62.5 degreesC, L. monocytogenes in slurry that contained SPP wer e killed too rapidly to allow determination of the D-value. Addition of 0.5 % SPP further decreased (P < 0.05) the heat resistance of L. monocytogenes in pork slurry hut not in ground pork The z-values in slurry ranged from 4. 63 to 5.47 degreesC whereas higher z-values (5.25 to 5.77 degreesC) were ob tained in ground pork. Degradation of SPP to orthophosphates in ground pork was two or three times greater than in pork slurry Possible reasons for fa ilure of SPP to reduce the thermal resistance of L, monocytogenes in ground pork are discussed. (C) 2001 Academic Press.