Enzyme Immunoassay for Phycocyanin as the Main Component of Spirulina Color in Foods

An enzyme immunoassay (EIA) for phycocyanin in foods was developed. Anti-phycocyanin monoclonal antibodies were obtained from A/J mice immunized with phycocyanin. The phycocyanin in a food was extracted by dissolving the sample in a borate buffer solution, pH 8.0 (BBS) and adjusting the pH value of this solution to 8.0 with NaOH. The extract was then diluted more than 10 fold with 1% gelatin in BBS. Phycocyanin was determined by avidin-biotin sandwich EIA, using the P26-8 monoclonal antibody as the solid-phase antibody and the P277-4 monoclonal antibody as the enzyme-labeled antibody. The working range for a quantitative analysis was 100-1000 ng/ml, and the detection limit was 10 micrograms/g of the original sample. Recoveries of phycocyanin from foods by this assay were > 71% for candy, and > 66% for ice cream and sherbet. Phycocyanin was assayed in 22 blue-, green-, purple-, and brown-colored commercial foods, and detected in one green colored-jelly at 49 micrograms/g.