Comparative Analysis Of Flavor Compounds Of Traditional And Industrial Fermented Soybean Pastes

In this experiment,solid-phase microextraction(SPME)coupled with gas chromatography–mass spectrometry(GC-MS)and static headspace gas chromatography(SHS-GC)were used to determine the total and main volatile flavor compounds in soybean pastes fermented by different processes(traditionally and industrially).Cluster analysis and sensory evaluation were used to verify the main flavor.The acidimetry method was used to analyze amino acid nitrogen,and the isoflavone and saponin contents were analyzed by high performance liquid chromatography(HPLC)in different fermented soybean pastes,their effects of volatile contents on flavor were preliminarily studied.Gas chromatography(GC)and automatic amino acid analyzer were used to analyze fatty acids and amino acids,respectively.The correlation between amino acids and fatty acids were also analyzed in combination with volatile flavor compounds.The study has laid the foundation for the industrial production of traditional food and the identification of strains which generate main flavor of fermented soybean pastes.The results are as follows:1.Volatile flavor compounds in different fermented soybean pastes measured by SPME-GC-MS were 67 and 61 out of which 29 were common compounds of flavor,including 3 types of aldehyde,4 types of alcohol,6 types of ester,8 types of acid,5 types of alkane,2 types of phenol and 1 type of azole.Although the number of volatile compounds identified was relatively close,the differences are obvious.2.SHS-GC was optimized to measure 16 volatile flavor compounds in the fermented soybean paste at one time.The conditions for static headspace sampler were optimized which showed that 4 m L sample load,50 min equilibration time and 80? of equilibration temperature gave us the desired output.Results showed that ethanol,butyric acid,2-pentylfuran,1-octen-3-ol and phenethyl alcohol were mainly volatile flavor compounds in the traditional fermented soybean paste,while 3-methyl-butyraldehyd and acetophenone were mainly volatile flavor compounds in the industrial fermented soybean paste.In addition,pyrazines are main flavor compounds of the traditional fermented soybean paste,2,6-dimethyl pyrazine was also detected in the industrial fermented soybean paste in this experiment.3.Results indicated that the contents of saponin and isoflavone in different fermented soybean pastes were significantly different(p<0.05)from each other.The contents of saponin Bb and Bd(0.86 and 0.11 mg/g,respectively)in the traditional fermented soybean paste were higher(p<0.05),while the contents of saponin Aa and Ab(0.24 and 0.33 mg/g,respectively)were higher(p<0.05)in the industrial fermented soybean paste.Traditional fermented soybean paste has higher aglycon-type glycitein,while industrial fermented soybean paste has higher(p<0.05)glycoside-type soy isoflavones.4.Amino acids and fatty acids affect the formation of flavor substances but in this experiment,the fatty acids content of different fermented soybean pastes were not significantly(p>0.05)different and has no significant(p>0.05)correlation with flavor components.In terms of amino acids,traditional fermented soybean paste has higher(p<0.05)contents of glutamic acid,alanine and tyrosine which were 1.99,0.51 and 0.18%,respectively.And industrial fermented soybean paste has higher(p<0.05)serine,isoleucine,lysine and proline contents which were 0.39,0.35,0.43 and 0.73%,respectively.Most amino acids showed correlations with various flavor compounds like alanine,tyrosine,histidine and glutamic acid has significant(p<0.05)positive correlations.