ENZYME-IMMUNOASSAY FOR CARMINIC ACID IN FOODS

A competitive enzyme immunoassay (EIA) for carminic acid was investiga ted, Monoclonal anti-carminic acid antibody was obtained from A/J mice immunized with carminic acid-human immunoglobulin G (IgG) conjugate, Carminic acid was extracted with distilled water from beverage, jelly, candy, pasta sauce, yogurt, or ice cream samples, Ham or fish paste s amples were digested with pronase, then carminic acid was extracted fr om samples with sodium hydroxide solution. The extract was diluted mor e than 10-fold with 1% gelatin in berate buffer solution, Microtiter p lates were coated with carminic acid-bovine serum albumin (BSA) conjug ate or just BSA, Goat anti-mouse IgG(H+L)-peroxidase complex was used as a second antibody, and 3,3',5,5'-tetramethylbenzidine was used as a substrate for the peroxidase, The working range for quantitative anal ysis was 0.3-10 ng/mL, and the detection limit was 0.2 mu g/g original sample, Recoveries of carminic acid by this assay were >95% for milk beverage and jelly, and >85% for yogurt and fish paste, Carminic acid was detected in 7 of 26 red-colored commercial food products and range d from 3.5 to 356 mu g/g. This EIA system also responded to the struct ural analogue of carminic acid, laccaic acid.