NITROGEN FERTILIZATION AND THE FORMATION OF 2‐PYRROLIDONE‐5‐CARBOXYLIC ACID IN STORED AND PROCESSED TABLE BEETS

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Abstract
SUMMARY —The conversion of glutamine to the bitter compound, 2‐pyrrolidone‐5‐carboxylic acid (PCA), in table beets was studied. Glutamine was analyzed by a phosphate‐buffer hydrolysis and distillation method. PCA was extracted with ethyl acetate and the ditrimethylsilyl derivative prepared and measured quantitatively by gas‐liquid chromatography. The accumulation of glutamine in fresh beets with excessive amounts of nitrogen fertilization caused a substantial increase in PCA content of processed beets. Conversion of glutamine to PCA in beets was proportional to the heating time during processing. Glutamine content did not alter during raw beet storage periods at 35°F; PCA content increased gradually.