Considerations of critical microorganisms and indicator enzymes in connection with the pasteurization of meat products

The first part of the work gives a general survey on critical microorganism s with regard to the pasteurization of meat products. Comparison of heat re sistance of two microorganisms, under isothermal conditions, is not problem atic when both survivor curves follow first-order or nth order inactivation kinetics provided that reaction orders are the same. If not so or, when su rvivor curves follow different types of inactivation kinetics, a more compl ex situation arises. It is obvious that, when z-values of the microrganisms to be compared differ considerably, z(A)not equal z(B) the order of size o f their heat resistance may be temperature dependent. The equivalent pasteu rization time (EPT) is analogous with the sterilizing (F) value, but the ch osen reference temperature is below 100 degrees C. In the present work, z a nd D values of various non-sporeforming microorganisms were collected from the literature, 12D values were calculated for 60, 70 (= T-ref) and 80 degr ees C and compared with those of 'Str. faecalis-D' selected for basis of co mparison. Results demonstrated that, depending on temperature, Lb. viridesc ens, Moraxella-Acinetobacter and some members of Lancefield D. group of str eptococci appear somewhat more heat resistant than 'Str. faecalis-D'. Probl ems of applicability of the acid phosphatase in meat as a potential indicat or enzyme when its z-value is not identical with the z value of the critica l ('target') microorganism, are also discussed. The EPT value of the entire heat processing curve, measured in the centre of the product, was calculat ed by the well known Bigelow's 'general method' and the above-mentioned con siderations were extended to non-isothermal heating conditions. (C) 1998 El sevier Science Ltd. All rights reserved.