Study on the Gibberellic Acid Residues in Brewing

Abstract

Gibberellic acid is a plant growth regulator, which can improve the quality of malts when used in the malting process, but it has a potential toxicity. The purpose of this study was to investigate the changes of gibberellic acid (GA3 in particular) during beer brewing process. GA3 residues in 15 kinds of commercial malt and 35 kinds of commercial beer were detected by ultra performance liquid chromatography-mass spectrometry (UPLC-MS). The GA3 residues in all of the malts were proved to be in direct proportion to the use of exogenous GA3 amount. In contrast, the GA3 residues were not detected in any of the selected beer samples. To find its cause, the levels of GA3 residues during mashing and boiling periods were measured. It was found that the GA3 in malts were isomerized in mashing and wort boiling stages, and a new substance with different retention characteristics compared with GA3 was observed in the C18 column. The mass-to-charge ratio (m/z) of the major ions for the new substance were m/z = 369.1 ([M+Na]+), m/z = 715.2 ([2M+Na]+), m/z = 329.2 ([M−H2O+H]+), m/z = 283.1 ([M−H2O−HCO2H+H]+). So, the new substance may be different from GA3 in the position of one or more groups. The new isomeric compound may be one of the GA3 isomers from the wort production. In further research, two dimensional nuclear magnetic resonance (2D NMR) will be used to identify the accurate structure of the new substance.