Bioassay for nisin in sausage; a shelf life study of nisin in cooked sausage.

A bioassay for nisin, an antimicrobial peptide used as a food additive, was developed for sausages based on nisin induced GFP-fluorescence (green fluorescent protein), and that could be performed on a microplate. The amount of GFP-fluorescence was easily measurable and dependent on nisin concentration. This GFP-bioassay for nisin had a detection limit in sausage as low as 0.9 ppm (0.9 μg/g), and it was used to assay shelf life of nisin in cooked sausage. Of the added nisin 68% could be detected from the sausages after storage of 28 days at 6 °C.