Rapid analytical extraction of volatile fermentation products

Solvent desorption dynamic headspace sampling of fermented dairy product volatiles

A method was developed based on solvent desorption dynamic headspace analysis for the identification and relative quantification of volatiles significant to the study of fermented dairy product aroma. Descriptions of applications of this method are presented including the measurement of diacetyl and acetoin in fermented milk, the evaluation of volatile-hydrocolloid interactions in dairy-based matrices, and the identification of volatiles in cheeses for canonical discriminative analysis. Advantages of this method include rapid analysis, minimal equipment investment, and the ability to analyze samples with traditional GC split/splitless inlet systems. Limitations of this method are that the sample must be in the liquid state and the inherent analytical limitation to those compounds that do not coelute with the solvent or solvent impurity peaks.

Use of Gas-Liquid Chromatography to Determine the End Products of Growth of Lactic Acid Bacteria

A simple gas-liquid chromatographic procedure for analyzing ethanol, acetic acid, acetoin, and racemic and meso -2,3-butylene glycol in broth media is described. Overnight broth cultures were filtered or centrifuged, and the filtrate or supernatant was treated with formic acid to aid separation of volatile fatty acids. Samples were then directly analyzed by gas-liquid chromatography on a 20% Tween 80-Chromosorb W-AW column and propionic acid as an internal standard. A complete analysis took ca. 8 min. The method can be used to distinguish homofermentative from heterofermentative lactic acid bacteria based on the level of ethanol produced and citrate-utilizing from non-citrate-utilizing lactic acid bacteria based on the levels of acetic acid produced. The method also has potential in distinguishing other bacterial fermentations. Of the 13 species of lactic acid bacteria tested, Streptococcus lactis subsp. diacetylactis was the major producer of 2,3-butylene glycol (total range, 0.3 to 3.5 mM), and, except for strain DRC1, both the racemic and meso isomers were produced in approximately equal amounts.