Identification and Quantitation of the Primary Chemicals Responsible for the Characteristic Malodor of Beet Sugar by Purge and Trap GC-MS-OD Techniques

Abstract

Seven samples of beet sugar with varying intensities of a characteristic beet sugar odor defect are analyzed to identify the chemicals responsible for the odor. Two purge and trap gas chromatographic (GC) procedures are investigated: closed-loop stripping analysis (CLSA) and direct thermal desorption (DTD). Detection for both methods is based on mass spectrometry and olfactometry. The aroma attributes of approximately 26 peaks are identified and characterized. Of these, only geosmin, 2,5-dimethylpyrazine, furfural, butyric acid, and isovaleric acid are judged to be likely contributors to the characteristic odor defect. Quantitative results for 2,5-dimethylpyrazine, butyric acid, and isovaleric acid are obtained with an ion trap detector (ITD) by DTD-GC of sugar samples. Samples are analyzed for geosmin by CLSA-GC-ITD and for furfural by high-performance liquid chromatography. Determination of olfactory threshold levels of each possible odor contributor is made by spiking odorless cane sugar with various levels and combinations of the five likely candidates. Combining quantitative results with olfactory sensory paneling results shows that the odor defect common to beet sugar is caused by the combination of geosmin and volatile organic acids.