EFFECT OF PH AND COOKING TEMPERATURE ON THE STABILITY OF ORGANOPHOSPHATE PESTICIDES IN BEEF MUSCLE

Temperature and pH stabilities of parent organophosphate pesticides (OPs) were investigated in lean (7.7% fat) beef muscle. Raw (pH 5.5) and pH-adjusted (pH 4.5 and 6.5) meat samples were fortified with mixtures of OPs to 1 ppm. Thermostability of OPs was studied by heating fortified meat samples to an endpoint of 71 or 77 degrees C. Compounds were extracted from fortified raw and cooked meat samples and analyzed by HPLC on a C-18 reversed-phase column. Parent OPs were stable in uncooked meat at pH 4.5, and their concentration progressively decreased with increase of pH from 5.5 to 6.5. Combined effects of pH and temperature were more efficient than pH and temperature alone in partly reducing levels of OPs in cooked meat. However, some compounds were susceptible to heat degradation in meat at pH 4.5, whereas others were readily degraded at pH 6.5. Overall, combination of all pHs and cooking temperatures significantly (p < 0.05) reduced concentrations of OPs in meat.