Acid phosphatase activity and color changes in consumer-style griddle-cooked ground beef patties

The U.S. Department of Agriculture and the Food and Drug Administration hav e issued temperature requirements to help consumers cook beef patty product s that are free of pathogens. Verification of end-point temperature (EPT) i s needed in cooked meat products due to concerns over outbreaks of Escheric hia coli 0157:H7. Acid phosphatase (ACP) activity was studied as a potentia l method for determination of EPT in ground beef patties cooked nonfrozen, patties frozen 7 days and thawed at room temperature 4 h in a refrigerator or by microwave, and patties made from ground beef frozen in store packages , then thawed in a refrigerator overnight. Pressed-out meat juices were ana lyzed from patties (n = 314) cooked to 57.2 degreesC (135 degreesF), 65.6 d egreesC (150 degreesF), 71.1 degreesC (160 degreesF), and 79.4 degreesC (17 5 degreesF) target EPTs. Expressed meat juice and internal meat patty color decreased in redness as EPT increased. Freezing whole packs with slow refr igerator or room temperature thawing caused significantly greater loss of r edness in expressed cooked meat juice than did other handling methods. Log( 10) ACP had a significant linear (R-2 = 0.99) response to EPT. Results show that the 3- to 5-min ACP test could be used to verify EPT in griddle-cooke d hamburger patties.