J. Soc. Cosmet. Chem. 26 277-288 (1975) ¸ 1975 Society of Cosmetic Chemists of Great Britain The relationship between water-borne bacteria and spoilage shampoo S. A. MALCOLM and R. C. S. WOODROFFE*t Presented on 28th August 1974 in London at the IFSCC VIIIth International Congress on 'Cosmetics--Quality and Safety' organized by the Society of Costmetic Chemists of Great Britain Synopsis--BACTERIA capable of surviving and multiplying in SHAMPOOS appear to repre- sent only a very small proportion of the total population carried by mains WATER. Examina- tions of mains water (from a single source) showed these bacteria occurring with a frequency of approximately 5 in 100 1. The ability of small numbers of bacteria to initiate heavy contamination in shampoos is unrelated to the volume of product inoculated. As few as 50 bacteria are capable of initiating contamination in 1 kg of shampoo and this same small number may be capable of initiating contamination in much larger volumes, e.g. a factory batch. The implications of this observation on the methods of detection of contamination and the time after manufacture at which products should be examined for the presence of contaminants are discussed. INTRODUCTION The microbiological quality of process water in the food industry has been of concern to manufacturers for many years. It is only comparatively recently, however, that the same concern has been shown in the manu- facture of toiletries and cosmetics. * Unilever Research, Isleworth Laboratory, Isleworth, Middlesex. ? R. C. S. Woodroffe died in December 1974. 277

278 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Originally the reported contaminants of toiletries and cosmetics covered a wide spectrum of organisms (1). However, more recent reports show that the typical product contaminant is in fact drawn from a much narrower range of organisms (2-7). The discrepancy between earlier and more recent reports is due to the fact that earlier investigators failed to differentiate between multiplying contaminants and those which were merely chance residents or transients. The most frequently reported con- taminants in recent years have belonged to such genera as Pseudornonas, Klebsiella, ,4chromobacter and ,41caligenes. These bacteria are common residents in water, both fresh (8-12) and distilled (13, 14) and it is now widely believed that the water used in the preparation of toiletry products is their likely source (11, 15, 16). In the UK mains water as supplied generally contains low numbers of bacteria (usually less than 300 ml -•) and if water were used in this condition it seems probable that it would contaminate only the more susceptible pro- ducts since it is likely that contaminants capable of multiplication in products represent only a small proportion of water flora. However, in the pro- duction of toiletries it is not always possible to use water directly from the main and it is frequently held in a storage tank before use. The ability of water-borne bacteria to multiply on storage is well known (9, 16, 17) and total counts of greater than 10 ? ml -• have been recorded (18). Indeed the readiness with which bacteria will multiply in stored water has led Cham- bers and Clark (11) to suggest that an absence of bacteria indicates that the water is toxic. Growth is probably at the expense of organic materials and salts present in the water (9) and perhaps materials dissolving in the water from the container (19). Growth may also be at the expense of dissolved volatile organic materials if these are used in the vicinity of the storage tank (20). Multiplication of bacteria will occur in pipelines where velocities are low (21) and it has been reported that polythene pipelines are prone to support- ing large growths of bacteria, sufficient oven to block the pipes (9), although Burman (22) has claimed that polythene piping has little effect on bacterial numbers. There is little question, however, that deionizing columns are sites at which bacterial numbers may increase (1 l, 23, 24). The bed concentrates Ca = + and Mg =+ from the water and at the same time collects organic materials by a process of sieving (24). The bacteria present in the water are either entrapped within the matrix of the bed or adsorbed on to the resin surface and so act as the inoculum. The numbers of bacteria in the effluent