Title Page
ABSTRACT
국문 초록
PREFACE
Contents
NOMENCLATURE 19
1. INTRODUCTION 20
1.1. Fermented soybean products 20
1.2. Cheonggukjang 24
1.3. Biogenic amines in Cheonggukjang 26
1.3.1. Biogenic amines 26
1.3.2. Biogenic amine contents in Cheonggukjang 30
1.3.3. Enterococcus faecium 33
1.3.4. Bacillus spp. 34
1.3.5. BA production by microorganisms in Cheonggukjang 35
1.3.6. Reduction of BAs in fermented foods 37
1.4. Objective of this study 38
2. Material and Methods 40
2.1. Bacterial strains 40
2.2. In-vitro assay 41
2.2.1. Determination of BA production by Bacillus strain 41
2.2.2. Determination of histamine and tyramine degradation by Bacillus strains 43
2.2.3. Determination of inhibitory effects of food additives on BA production 46
2.3. Identification of Bacillus strains 47
2.4. Cheonggukjang fermentation 47
2.4.1. Cheonggukjang fermentation with the selected Bacillus strains capable of degrading toxic BAs 47
2.4.2. Cheonggukjang fermentation with the selected food additives capable of reducing toxic BAs 52
2.5. Measurements of physicochemical and microbiological properties 54
2.6. BA analysis in Cheonggukjang samples 55
2.6.1. BA extraction from Cheonggukjang samples and bacterial cultures for HPLC analysis 55
2.6.2. Standard solutions preparation for HPLC analysis 56
2.6.3. Derivatization of extracts and standards 56
2.6.4. Chromatographic separations 57
2.7. Statistical analysis 58
3. Results and Discussion 59
3.1. Degradation of toxic BAs by Bacillus strains isolated from Cheonggukjang products 59
3.2. Effects of toxic BA-degrading Bacillus strains on food quality parameters and BA content in Cheonggukjang 64
3.2.1. Effects of toxic BA-degrading Bacillus strains on the physicochemical and microbiological parameters of Cheonggukjang 64
3.2.2. Effects of toxic BA-degrading Bacillus strains on BA content in Cheonggukjang 68
3.3. Effects of toxic BA-degrading Bacillus strains on food quality parameters and BA content in Cheonggukjang contaminated with tyramine-producing E. faecium 77
3.3.1. Effects of toxic BA-degrading Bacillus strains on physicochemical and microbiological parameters of Cheonggukjang contaminated with tyramine-producing E. faecium 78
3.3.2. Effects of toxic BA-degrading Bacillus strains on BA content in Cheonggukjang contaminated with tyramine-producing E. faecium 81
3.4. Inhibitory effects of food additives on tyramine production of Enterococcus and Bacillus strains in assay media 90
3.5. Effects of food additives on food quality parameters and BA content in Cheonggukjang contaminated with tyramine-producing Bacillus and Enterococcus strains 95
3.5.1. Effects of food additives on physicochemical and microbiological parameters of Cheonggukjang 96
3.5.2. Inhibitory effects of food additives on BA formation in Cheonggukjang 100
4. CONCLUSION 109
REFERENCES 112
Table 1. Biogenic amine content in Cheonggukjang products. 32
Table 2. Composition of culture medium used for BA production test. 42
Table 3. Composition of buffer used for toxic BA degradation test 44
Table 4. Composition of culture medium used for toxic BA degradation test 45
Table 5. Ingredients used for preparation of BacNon group 50
Table 6. Ingredients used for preparation of BacEnt group 51
Table 7. Ingredients used for preparation of Chenoggukjang fermentation with food additivies 53
Table 8. In vitro production and degradation of histamine and tyramine by Bacillus strains isolated from Cheonggukjang 61
Table 9. In vitro productivity of histamine and tyramine by selected Bacillus strains originating from Cheonggukjang 62
Table 10. In vitro degradation rates of histamine and tyramine by selected Bacillus strains originating from Cheonggukjang 63
Table 11. Changes in BA content during the fermentation of Cheonggukjang inoculated with Bacillus strains (BacNon group) 74
Table 12. Degradation rates of histamine, tyramine, and spermine by B. licheniformis CH7P22 during the fermentation of Cheonggukjang with and without E. faecium contamination. 75
Table 13. Changes in BA content during the fermentation of Cheonggukjang inoculated with Bacillus strains along with an E. faecium strain (BacEnt group) 87
Table 14. Effects of food additives on tyramine production in assay media 93
Table 15. Effects of food additives on bacterial counts in assay media 94
Figure 1. Cheonggukjang production process 22
Figure 2. Representative fermented soybean products from Japan, China, and Korea. 23
Figure 3. Structure of BAs and respective precursors. 29
Figure 4. Changes in physicochemical and microbiological properties during the fermentation of Cheonggukjang inoculated with Bacillus strains (BacNon group). (a) pH, (b)... 67
Figure 5. Changes in (a) tyramine, (b) histamine, and (c) spermine content during the fermentation of Cheonggukjang inoculated with Bacillus strains (BacNon group). ●: B... 73
Figure 6. Cheonggukjang of BacNon group on day 4 of fermentation 76
Figure 7. Changes in physicochemical and microbiological properties during the fermentation of Cheonggukjang inoculated with Bacillus strains along with an E. faecium... 80
Figure 8. Changes in (a) tyramine, (b) histamine, and (c) spermine content during the fermentation of Cheonggukjang inoculated with Bacillus strains along with an E. faecium... 86
Figure 9. Cheonggukjang of BacEnt group on day 4 of fermentation 88
Figure 10. Comparison of tyramine formation during the fermentation of heonggukjang with and without E. faecium contamination. ■: NC1 sample inoculated with B. licheniformis... 89
Figure 11. Changes in physicochemical and microbiological properties during the fermentation of Cheonggukjang inoculated with prolific tyramine producing B. subtils CB... 99
Figure 12. Changes in (a) tyramine, (b) spermidine, (c) spermine, (d) putrescine, and (e) cadaverine during the fermentation of Cheonggukjang inoculated with prolific tyramine... 107
Figure 13. Cheonggukjang treated with food additives on day 4 of fermentation 108