Concord grapes, chromatogram

Figure F1.3.3 HPLC chromatogram of concord grape juice. Peaks identified on figure.

Figure FI. 3.4 shows HPLC chromatograms for anthocyanidins generated from acid hydrolysis of concord grape and strawberry juices. Extraneous peaks may be present because of incomplete hydrolysis, and degradation and polymerization of the labile aglycons even more of a problem. For acylated anthocyanins, higher yields of anthocyanidins will be achieved if the sample is first saponified (see Basic Protocol 3) and then subjected to acid hydrolysis (see Basic Protocol 2).

Figure G1.1.3 FID gas chromatogram of a direct injection of the headspace above concentrated extract of Concord grape essence using OV101 substrate. Note the size of the methyl anthranilate peak and the absence of a convincing peak for p-damascenone.

Figure G1.1.3 shows a chromatogram of the headspace of Concord grape essence prepared by direct injection. At retention index 1320 is the peak caused by methyl anthranilate, one of the strongest odorants characterizing Concord grapes however, (i-damascenone, the second most potent odorant in Concord grapes, elutes at 1360 but is not visible. This is because P-damascenone is lOOOx more potent (i.e., its odor threshold is lOOOx lower than methyl anthranilate). This is typical result for the direct injection of headspace from natural products. Figure Gl.1.4, on the other hand, shows the injection of an extract of Concord grape essence concentrated 500-fold with the fi-damascenone peak large enough for quantitation.

Figured.1.4 An FID chromatogram of concentrated extract of the same Concord grape essence shown Figure G1.1.3, drawn to display the data on a linear retention index scale. By simply comparing the index of a peak with the data listed in the flavornet, the odorants that have similar retention indices can be determined. Notice how large the methyl anthranilate peak is, but still no convincing peak for p-damascenone, even though both compounds have the same odor activity (intensity).

Figure 11.3.12 HPLC chromatograms of polyphenolics in Concord grape extract detected at 280 nm. (A) All polyphenolics, including anthocyanins. (B) Nonanthocyanin polyphenolics after fractionation. Peak identification 1, cis-caftaric acid 2, frans-caftaric acid 3, procyanidin B3 4, c/s-coutaric acid 5, frans-coutaric acid 6, epicatechin 7, quercetin galactoside 8, quercetin glucoside. Reproduced from Oszmianski and Lee (1990) with permission from the American Society for Enology and Viticulture.

Figure 1. Gas chromatograms from a Freon 113 extract of Concord grape juice concentrated 3,500 times (top) and the 3% ether-pentane fraction of a Florisil separation of the whole Freon 113 extract concentrated 13,000 times (bottom). The dots show regions where odor was detected. Conditions 30 m 0.3 mm carbowax 20 M column, helium gas flow of 23 cm sec programmed...

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