R. L. Wilson

Evaluation of Creatine Phosphokinase Activity as a Means of Determining Cooking End-Point Temperature

The influence of cooking end-point temperatures (EPTs) of 62.8, 66.7, 67.8, 68.9, 70.0, 71.1, 73.9, and 76.7°C on residual creatine phosphokinase (CPK) activity in laboratory prepared model systems of ground chicken and turkey breast meat was determined. CPK activity was also assayed in commercially prepared chicken, turkey, and meat products using a Sigma #661 CPK test kit. Three tenths milliliter of 0.9% saline extracts obtained from the chicken, turkey, and meat products was substituted for 0.3 ml serum specified in the test kit procedure. For the model samples, there was a marked decrease in CPK activity as EPT increased from 66.7 to 76.7°C; however, model samples heated to 76.7°C did retain low amounts of CPK activity. In general, very low levels of CPK were found in commercially prepared chicken and turkey products (0 to 10.6 Sigma units/ml). Results of CPK activity in commercially prepared meat products would indicate that the test is product dependent, with values ranging from zero for beef franks to 258 Sigma units/ml for hard salami. Thus, while CPK activity may be useful for detecting cooking EPT for quality control purposes, it should not be used as a regulatory procedure where experience with the specific product is not available.

Glutamic-Oxaloacetic Transaminase Activity: A Potential End-Point-Temperature Indicator for Imported Cooked Beef†

Glutamic-oxaloacetic transaminase (GOT) activities in thermally processed beef samples were determined with a diagnostic test kit (no. 505P, Transaminases ALT/GPT and AST/GOT, Sigma Chemical Co.) procedure for possible use as indicators of cooking end-point temperatures (EPTs) between 71.1 and 82.2°C. GOT activity in the beef samples decreased curvilinearly with increasing EPTs. Activity was 3,450, 120, and 6 Sigma-Frankel units/ml (SFUs/ml) at 71.1, 75.6, and 82.2°C, respectively; a reduction of 99.8%. GOT values at 78.9,79.4, and 80.0°C, the critical range of EPTs in evaluating beef logs imported from South America, were 31, 17, and 14 SFUs/ml, respectively. Values within this range of temperatures differed significantly (P < 0.05); we suggest that residual GOT activity may be used as an EPT indicator for imported cooked beef products.

Evaluation of a Sound Velocity Analyzer for Estimating Maximum Internal Temperature to Which Meat Products Have Been Heat Processed

The sound velocity (SV) values of a variety of solutions (distilled water, saline, silicon dioxide, bovine serum albumin, coagulated beef protein) were determined as the temperature of the solution was increased from 10 or 20° to 71°C. Few differences were found in the SV values for the various types of distilled water; however, there was an increase in SV values as the concentration of saline increased. Level of silicon dioxide or bovine serum albumin had no significant effect on SV values; however, there was an increase in SV values as percentage of precoagulated beef protein solids in solution increased. The sound velocity analyzer used in this study was found not to be sensitive enough to detect the onset of coagulation of saline soluble proteins and, therefore, would not lend itself as an objective method which could be related to end-point temperature of meat products.