Metabolomics Analysis\nReveals Bitter Taste Formation\nin off-Season Crab Hepatopancreas Marketed in June of the Lunar Calendar

Crabs marketed off-season in lunar June often have a\nbrown hepatopancreas\n(BH) that tastes bitter, unlike the nonbitter orange hepatopancreas\n(OH). We conducted nontargeted and widely targeted metabolomics analyses\non both raw and cooked orange and brown hepatopancreas of <i>Eriocheir sinensis</i>. A total of 115 bitter metabolites were\nidentified, including oxylipins, amino acids, small peptides, nucleotides,\nvitamins, and coenzymes. Targeted quantitative analysis revealed that\nseven oxylipins were major contributors to the bitterness of BH. The\nprimary metabolic pathways affecting hepatopancreas bitterness involved\nthe production of unsaturated fatty acids and α-linolenic acid\nmetabolism. Furthermore, specific odorants were produced from OH and\nBH groups during heat treatment, namely ethyl caproate and methional,\nrespectively. Moreover, differential metabolites were found to act\nas odor precursors, resulting in a brown and bitter hepatopancreas\nwith poor odor quality. This study elucidates the generation of bitter\nsubstances in the hepatopancreas of <i>Eriocheir sinensis</i> through metabolic pathways and thermal reaction pathways.