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A microbial sensor system, based on the use of immobilized Arthrobacter nicotiana and an oxygen electrode, was applied to determine free short-chain fatty acids in raw milk samples and the result was compared with gas chromatography (GC) and a titrimetric method. The sensor response was linearly related to the concentration of short-chain fatty acids obtained by GC (n = 10, r = 0.92) and to the total concentration of free fatty acids obtained by titrimetric measurement (n = 10, r = 0.78). This result suggests that the present microbial sensor can selectively determine free short-chain fatty acids in raw milk samples and may be useful as a very fast detection method of rancidity in milk.

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On the occasion of a storage test in order to evaluate the tightness of milk packing materials to permeating flavours by sensory analysis the statistical method for judging the concerned assessors recommended by Römer and Renner was applied. We gained the experience, that this method allows no statement about the assessor's sensory ability at all, but merely fixes his order of precedence in a panel as to his ability to realize sensory differences in the scope of one special problem. The mentioned statistical procedure cannot substitute a selection of assessors aimed at the subject of the following sensory analysis.

The mass-spectroscopical identification of aflatoxines in the eluant after thin-layer-chromatographical seperation represents a problem at amounts of less than 50 ng normally found in foods. Therefore it was necessary to investigate the factors influencing the identification. Among others, influences of plate material and the eluant were found. Based on the results with pure aflatoxines ideas were developed on their possible reactions.