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The Palatability of Food Exposed to o-Chlorobenzylidene Malononitrile (CS)

The possibility that food seriously contaminated with o-chlorobenzylidene malononitrile (CS) might be inadvertently swallowed was investigated by exposing a limited range of foodstuffs to CS aerosols and determining whether contaminated items could be identified by tasting panels. The scope of the investigation was curtailed by the reluctance of volunteers to sample the foods, but the experiments which were completed indicated that human subjects were aware of contamination at levels considerably below those likely to present any hazard to health. A consequence of the use of CS in urban areas might be the contamination of foodstuffs in homes or in shops. Whilst it is highly improbable (Report of the Enquiry into the Medical and Toxicological Aspects of CS (o-Chlorobenzylidene Malononitrile), Part 2, 1971), under normal operational conditions, that concentrations of CS smoke would be produced which could cause food contamination, the ability of human subjects to detect any change in the palatability of food which has been exposed to CS is of importance when considering possible dangers from the relatively high concentrations which might result from the burning of a CS device in a closed room or store. Although some individuals claim that they can identify CS in extremely low concentrations, the existence of a characteristic taste or smell is very doubtful, and it seems more probable that CS acts as a non-specific stimulator of the ‘common chemical sense’ receptors present in mucous membranes. Currie, Chenier, and Stewart (1963) using small discrete drops of very dilute solutions of CS in polyethylene glycol, showed that, on the human tongue, threshold sensations were reported with concentrations of between 0·25 μg. per cm.3 and 0·50 μg. per cm3. More recent work (Ballantyne, 1971), using drops of solutions of CS in saline, indicated a median threshold of 1·3 μg. per cm.3 (95 per cent limits 1·1 to 2·0 μg. per cm.3). Whilst these findings show that very small quantities of CS may be detected in the mouth in the absence of other substances, they do not necessarily apply when other materials are present. Research in the food industry has shown that the effects on the palatability of food of ‘off flavours’ are extremely subtle and complex, and may be potentiated or suppressed by interaction with such factors as the appearance and mechanical properties of the food, and the physiological and psychological status of the subject, in addition to the more obvious variables of taste, smell, and pain usually associated with ‘flavour’ (Amerine, Pangborn, and Roessler, 1965). The study of all these variables and their interactions was impracticable in the circumstances of the present investigation, and the most appropriate approach appeared to be an empirical one in which real food was exposed to CS smoke under varying conditions to reproduce the various types of contamination which could take place. A systematic study of any acute or chronic consequences of ingesting CS-contaminated foods was beyond the scope of the study, although, in a single experiment, some grossly contaminated food was given to rabbits. From the outset, there was considerable difficulty in recruiting volunteers to sample the food, and this eventually caused the termination of the investigation, following some abortive experiments for which adequately-sized tasting panels could not be assembled. It was, therefore, impossible to examine many of the topics which it had been proposed to cover; nevertheless, the observations reported here clearly indicate certain conclusions regarding the palatability of contaminated food.