The Bacteriology of Surface-Taint Butter: A Review

Abstract

Surface taint became a problem to the dairy industry with the introduction of pasteurized cream for buttermaking. This heat treatment seems to transform the cream to a satisfactory medium for the growth of the causative organism. Butter churned from pasteurized cream that has been contaminated with Ps. putrefaciens usually develops a putrid odor and flavor within a very few days, even when stored at temperatures as low as 5° C. Ps. putrefaciens has been isolated most frequently from the water used in washing the butter and from various pieces of equipment in dairy plants encountering difficulty with surface taint. This organism is relatively easily inactivated by chlorine; therefore, adequate treatment of an infected water supply with this chemical will render it suitable for use in butter manufacture. In some instances, certain pieces of equipment such as wooden churns become so extensively infected with this organism that the replacement of a badly worn unit is the simplest method of stopping a bad outbreak of surface taint in the butter from a particular plant. The incidence of surface taint can be lowered very markedly by following good sanitary practices in the dairy plant. Several groups of investigators have made suggestions for the prevention and control of surface taint. Although the practical methods suggested for the control of this defect are quite effective, there is still no really rapid and simple procedure for determining whether any particular churning of suspected butter actually contains Ps. putrefaciens, and, if so, just how extensive the contamination with these organisms is. The quantitative estimation and isolation of Ps. putrefaciens from butter has been a problem worked on for many years by investigators in Australia, New Zealand, Canada and the United States. A large part of this research has been directed at the development of a more suitable medium for the growth of this organism. It has been apparent for quite some time that Ps. putrefaciens loses viability rather quickly when stored; hence, part of the difficulty encountered in recovering this organism from butter can be traced to the fact that the number of viable cells remaining in the infected sample may be very low. Also, there is very definite evidence that ordinary distilled water is highly toxic to Ps. putrefaciens; therefore, any technique employing unbuffered water as the dilution medium immediately lowers the possibility that any of the causative organisms will be recovered. Regardless of the technique used for the quantitative estimation or isolation of this organism from butter, it is imperative that as fresh samples as possible be obtained for analysis because of the rapid rate at which the organism loses viability on storage. © 1952, American Dairy Science Association. All rights reserved.