Quantitative analysis of pyrazines in a hydrophilic solid model system
1997
Jusino, M.G. | Ho, C.T. | Tong, C.H.
The requirements for accurate quantitative analysis of 2-methylpyrazine and 2,5-dimethylpyrazine thermally produced in a solid system consisting of 4.5% (w/w) lysine, 5.5% (w/w) glucose and granular starch with 10% moisture content (dry basis) were investigated. The ratios (or response factors) of the pyrazines to pyrimidine obtained from GC analysis remained constant after a 1000 fold concentration at 55C, verifying that pyrimidine was adequate as an internal standard to account for losses of the pyrazines during concentration. Calibration curves for both pyrazines constructed by plotting the response factors versus concentration were shown to be linear from 0-1000 ppm. However, the slope of the calibration curve was found to vary when constructed over 10 days, suggesting that it was necessary to construct daily calibration curves. Recovery Studies were conducted by adding known amounts of pyrazines to amioca starch without heating. The procedure using three extractions with methylene chloride gave adequate recovery efficiencies (100% +/- standard deviation) versus recoveries below 80% for two extractions. In order to completely recover the pyrazines thermally produced in the model system with methylene chloride, an extraction time of 72 h at room temperature was necessary which was believed to be due to the diffusion limited extraction of the pyrazines by the nonpolar solvent from the hydrophilic solid matrix.
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