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SUMMARY— Stepwise discriminant analysis for classifying food samples (known independently to differ in flavor) is illustrated by computer analysis of gas chromatograms from roasted coffee and potato chips. Four lots of coffee prepared so as to differ in flavor were scored organoleptically, steam distilled, and the distillate examined gas chromatographically. By calculating all possible ratios among peak heights and subjecting these ratios to discriminant analysis, the coffee could be classified into the four flavor categories from the gas chromatographic data. The discriminant analysis procedure was set to select the ratio most critical in differentiating among the chromatograms, then move on to the next most efficient ratio until the samples were classified. The same thing was done for potato chips except headspace volatiles were used for the gas chromatographic analysis. Not only does the procedure described enable flavor to be correlated with gas chromatographic data, but the efficiency values for each ratio are useful. A compound devoid of flavor can conceivably be highly correlated with flavor; however, there is a good chance that a compound highly correlated with flavor is a flavor substance itself.

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SUMMARY— The flavor threshold concentrations were determined for 23 compounds composing an artificial peach beverage base. The threshold levels ranged from 52 ppm to 0.4 ppb. The threshold values were used in sub‐threshold, additive sub‐threshold, and concentration trials. Sub‐threshold and additive sub‐threshold effects resulted from only a few of the flavor combinations tried. Change in concentration of one compound in a mixture of six compounds was not readily detectable organoleptically. The difference in concentration could be detected gas chromatographically, but only if the mixtures were extracted with pentane and concentrated. By dividing the respective threshold values into the amount of each compound present in the beverage, a factor was calculated, called the “unit flavor base,” which indicated the relative importance of each compound as a flavor substance in the peach beverage. By dividing the gas chromatographic peak heights by the respective threshold values, gas chromatographic response was weighted for flavor importance. When the unit flavor base and weighted gas chromatographic response were converted into logarithms, the relation between the values was nearly linear. The correlation coefficient was 0.8691 (significant @ 0.01).

Vanillin was subjet to O demethylation and supported growth of Clostridium formicoaceticum and Clostridium thermoaceticum. Vanillin was also stimulatory to the CO‐dependent growth of Peptostreptococcus productus. the aldehyde substituent of vanillin was metabolized by routes which were dependent upon both the acetogen and a co‐metabolizable substrate (e.g. carbon monoxide [CO]). C. formicoaceticum and C. thermoaceticum oxidized the aldehyde group of vanillin to the carboxyl level, while P. productus reduced the aldehyde group of vanillin to the alcohol level. In contrast, during CO‐dependent growth, C. thermoaceticum reduced 4‐hydroxybenzaldehyde to 4‐hydroxylbenzyl alcohol while P. productus both reduced and oxidized 4‐hydroxybenzaldehyde to 4‐hydroxybenzyl alcohol and 4‐hydroxybenzoate, respectively. These metabolic potentials indicate aromatic aldehydes may affect the flow of reductant during acetogenesis.