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Thesis (M.S.)—University of Nebraska—Lincoln, 1971. Department of Food Science and Technology.


Copyright 1971, the author. Used by permission.


The concept of microbial end product identification and quantitation has been recognized as an indirect method of evaluating the degree of bacterial contamination. Obtaining a method of accurately quantitating a representative bacterial end product at the microgram or submicrogram level presents a much needed analytical tool in the quality control and research laboratory. Recognizing that lactic acid is a common microbial metabolite, it is logical to pursue the quantitation of this compound.

Keeping the needs of extreme sensitivity and rapid analysis in mind, the use of gas liquid chromatography (GLC) instrumentation was employed. Selection of the proper detection system was of first interest to obtain sensitivity, linearity and reproducibility. The electron capture detector is one of the most sensitive methods of GLC analysis, having a capacity of detecting quantities at the 0.1 picogram level. The electron capture detector is responsive only to certain molecules such as alkyl halides, conjugated carbonyls, nitrites, nitrates and organometalics. Since lactic acid has none of the above functional groups, alteration of lactic acid in some controlled way was needed to obtain a product to which electron capture was responsive.

Advisors: R. Burt Maxcy and Roy G. Arnold