Masaki Miyabe

Survey of aflatoxin B1 and ochratoxin A in commercial green coffee beans by high‐performance liquid chromatography linked with immunoaffinity chromatography

The natural occurrence of aflatoxin B1 (AFB1) and ochratoxin A (OTA) has been surveyed in 47 samples of commercial green coffee beans. Samples were collected in Nagoya City, Japan, during 1988–93. Using a combination of immunoaffinity chromatography and high‐performance liquid chromatography analysis, AFB1 and OTA were quantified with detection limits of 2 ng kg‐1 and 0.1 μg kg‐1 respectively. Positive rates and levels of AFB1and OTA were 32% and 2.0–32.9 ng kg‐1, and 30% and 0.1–17.4 μg kg‐1 respectively. The samples contaminated with AFB1 or OTA were mainly imported from African and Asian countries, and several samples were found to be positive for these two mycotoxins for the first time in Japan, although their levels were low.

An improved indirect competitive Elisa for aflatoxin m1 in milk powders using novel monoclonal antibodies

Among three newly prepared monoclonal anti‐aflatoxin M1 antibodies, named AM.1, AM.2 and AM.3, both AM.1 and AM.3 possessed high specificity and sensitivity towards aflatoxin M1, while AM.2 exhibited lower specificity. Employing AM.3 and horseradish peroxidase‐labelled second antibody, an improved ELISA was developed with a detection limit of 1.0 pg ml‐1 of aflatoxin M1 in solution. The contents of aflatoxin M1 in powdered milks suspended in water were assayed by the indirect ELISA. The detection limit was 5 pg g‐1dry weight, and no clean‐up procedures were required. The reliability of the present ELISA with monoclonal antibody AM.3 was confirmed with reference powdered milks for aflatoxin M1. A limited ELISA survey showed the presence of aflatoxin M1 in commercial milk powders sampled in France, the US and Thailand at levels of 30–418 pg g‐1, and it was confirmed by an improved HPLC analysis.