The Liberation of Water-Insoluble Acids in Cream by Geotrichum Candidum

Open Access
Publisher Website
Google Scholar
Abstract
Recently attention has been directed to the lipolytic reaction in cream because the extent of lipolysis, as measured by the accumulation of water-insoluble acids (WIA), has been proposed as a means of evaluating the quality of cream and butter (6). Numerous studies have demonstrated that lipolysis of butterfat in raw cream results from the action of lipoelastic microorganisms andjor natural milk lipases. Lipolytic microorganisms, including Geotrichum candidwm, have been considered by some authors (3) to be of greater significance than milk lipase as a cause of fat hydrolysis in raw cream. Other investigators (8) have revealed that the natural milk lipases may cause significant increases in the WIA values of cream. Peters et al. (9) reported that the types of microorganisms, the amount of lipase present and the time and temperature of cream storage determine the degree to which WIA values change in a given sample of raw cream. Hillig et at. (6) attributed the inferior quality of some cream to improper production practices and reported that the rate of cream decomposition depends chiefly on the storage temperature. Water separation was considered also by these authors to be a contributing factor to early decomposition of cream. Babel (2) was unable to find a significant difference in the WIA content of butters nmde from raw cream held at 55 or 75 ° F. for periods up to 10 days. The same author indicated that when cream sours rapidly, the lipases are in- hibited because of the unfavorable pH. In addition, cream having a low acidity and containing putrefactive types of microorganisms usually produced butter with a high WIA content. Many investigations dealing with factors influencing the growth of lnold in cream and its significance in cream quality have been reported and summarized (4). ttowew~r, data demonstrating the release of WIA in cream by the m.tion of specific organisms are very meager. The purpose of this report is to pre- sent data which indic'ate that certain enviromnental factors have a profound influence upon the rate at which WIA are released in sterilized cream by the action of G. ea~did~lm. The data obtained serve to emphasize the lipolytie poten- tial of this commonly encountered dairy contaminant and demonstrate that G. ca~didum is capable of releasing unusually large quantities of WIA from the butterfat in ~.ream. EXPERIMENTAL PROCEDURE The rate at which G. candid~tm produces WIA from butterfat was studied by growing the test organism in sterilized cream incubated at 20 ° C. or other selected storage temperatures for a period of 9 days. WIA values of the sam- ples were determined at 3-day intervals during the incubation period.