Abstract: In this study, raw mustard and pickled mustards at different pickling stages as well as pickle juice were analyzed by RP-HPLC for their variations in organic acid contents. In the RP-HPLC analysis, the chromatographic column used was an Agilent TC type C18 column. The separation of organic acids was performed by using a mobile phase made up of 3% methanol and 0.5% KH2PO4 which adjusted to pH 2.8 with H3PO4 at a flow rate of 0.8 mL/min. The detection wavelength was set as 215 nm, and the column temperature was controlled at 17 ℃. Eight organic acids were separated effectively under these conditions. The organic acids exhibited a recovery rate varying between 95.73% and 100.55% and a relative standard deviation ranging from 2.04% to 3.12%. The RP-HPLC method had a good linear correlation and was accurate. Sonication was found to be better for extraction of organic acids than water bath heating and ethanol extraction. The contents of organic acids in pickled mustards and pickle juice increased as the pickling number increased from 1 to 3. The most predominant acid was lactic acid, which accounted for 29.94% and 38.55% of total organic acids in once pickled and twice pickled samples, respectively. The relative content of lactic acid was 73.50% during the late part of the third pickling cycle. Among all processing stages of mustard, rinsing had the largest impact on organic acids followed by manual acidity adjustment.

Key words: mustard, pickling, organic acids, changes