Study on the Gibberellic Acid Residues in Brewing

摘要

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 (GA_3 in particular) during beer brewing process. GA_3 residues in 15 kinds of commercial malt and 35 kinds of commercial beer were detected by ultra performance liquid chromatography-mass spec-trometry (UPLC-MS). The GA_3 residues in all of the malts were proved to be in direct proportion to the use of exogenous GA, amount. In contrast, the GA_3 residues were not detected in any of the selected beer samples. To find its cause, the levels of GA_3 residues during mashing and boiling periods were measured. It was found that the GA_3 in malts were isomerized in mashing and wort boiling stages, and a new substance with different retention characteristics compared with GA_3 was observed in the C|8 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-H_2O+H]~+), m/z = 283.1 ([M-H_2O-HCO_2H+HJ+). So, the new substance may be different from GA_3 in the position of one or more groups. The new isomeric compound may be one of the GA_3 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.