Isolation and identification of the bitter compound from Huangjiu

The strategy of taste-guided assisted by solvent extraction, solid-phase extraction and semipreparative HPLC were applied to isolate the main nonvolatile bitter components from mechanized Huangjiu. The potential fraction was identified by amino acid analysis and ultra-performance liquid chromatography-quadrupole-time-of-flight-MS/MS. Bitter pyroglutamate peptide Pyr-LFNPSTNPWHSP (PGP) was successfully identified from Huangjiu for the first time. Quantitative analysis showed that PGP contents ranged from below the limit of quantitation to 32.97 mg/L, among mechanized Huangjiu had higher contents than manual and commercial Huangjiu. The formation of PGP mainly occurred in the primary fermentation and it was stable in Huangjiu. Moreover, the PGP content of the Huangjiu brewed using raw wheat Qu was 112.6% higher than that using cooked wheat Qu, but presented subtle change with the increase of raw wheat Qu. The results revealed that PGP contributed the bitterness to Huangjiu, which may offer a possibility to reduce the bitterness of Huangjiu.