Separation of botulinum-positive and -negative fish samples by means of a pattern recognition method applied to headspace gas chromatograms.

A gas chromatographic headspace technique was used to analyze the gas produced during putrefaction of pond-raised, degutted trout, incubated in evacuated plastic pouches. The following samples were analyzed; 10 samples which, due to natural contamination with Clostridium botulinum, were toxic when injected into mice, 10 samples which were nontoxic when injected, and 9 samples inoculated with one strain of C. botulinum type E. The gas chromatograms showed the presence of 118 compounds in most samples. Quantitative differences among most chromatograms could be observed, but no compound was unique to any of the three groups. By means of a specific pattern recognition method, all negative samples were shown to fall into one group and were distinctly separated from the toxic samples. No differences could be observed between the two groups of inoculated and naturally contaminated trout samples. The results suggest that headspace analysis combined with pattern recognition analysis might prove to be a valuable method for screening studies of foods containing living cells of C. botulinum.