Microbial encapsulation for enhancing soy sauce aroma development during moromi fermentation

[摘要] Moromi fermentation is an essential part of soy sauce production. This thesis aimed to characterize and control the growth and interaction of two predominant microorganisms, Tetragenococcus halophilus and Zygosaccharomyces rouxii for enhancing the aroma development during moromi fermentation. Antagonism was observed between T. halophilus and Z. rouxii, regardless of the inoculation sequence. However, sequential inoculation of Z. rouxii resulted in more complex aroma profile than simultaneous inoculation. To eliminate antagonism, chitosan-coated alginate and water-oil-water (W1/O/W2) double emulsions (DEs) were tested for their ability to encapsulate Z. rouxii and stability in high NaCl solutions. Alginate was unstable in high NaCl solutions and chitosan exhibited undesirable antimicrobial activity towards Z. rouxii. DEs minimized the antagonism between T. halophilus and Z. rouxii, by segregation in the external W2 and internal W1 phase, respectively. Physicochemical changes in the fermentation medium indicated that DEs affected microbial growth and cell physiology, contributing to the elimination of antagonism. The destabilization of DEs over 30-day storage depended on glucose concentration in W2, which indicated a possibility of sustained release mechanism of Z. rouxii into the moromi. Furthermore, the application of DEs was tested in a moromi model, formulated with reduced NaCl and/or substitution with KCl. DEs resulted in moromi with similar microbiological and aroma profile to that of high-salt. Overall, this thesis demonstrates the potential of DE for delivering mixed cultures in moromi fermentation, which could be applicable in any fermentation process where multiple species are required to act sequentially.

[发布机构] University:University of Birmingham;Department:School of Chemical Engineering

[关键词] T Technology;TP Chemical technology