Bo Young Byun

Biogenic amine formation and bacterial contribution in Natto products

Twenty-one Natto products currently distributed in Korea were analysed for biogenic amine contents and tested to determine physicochemical and bacterial contributions to biogenic amine formation. Among them, nine products (about 43%) had β-phenylethylamine or tyramine contents greater than the toxic dose (30mg/kg and 100mg/kg, respectively) of each amine, although no products showed total amounts of biogenic amines above the harmful level (1000mg/kg), which indicates that the amounts of biogenic amines in some Natto products are not within the safe level for human health. From four different Natto products, that contained noticeable levels of β-phenylethylamine and tyramine, 80 bacterial strains were isolated. All the strains were identified to be Bacillus subtilis and highly capable of producing β-phenylethylamine and tyramine. Therefore, it seems likely that the remarkable contents of β-phenylethylamine and tyramine in Natto predominantly resulted from the strains highly capable of producing those amines present in the food.

Formation and destruction of biogenic amines in Chunjang (a black soybean paste) and Jajang (a black soybean sauce)

Chunjang and Jajang samples were analysed for biogenic amine contents by using HPLC equipped with a UV-Vis detector. Chunjang samples contained relatively large amounts of histamine (up to 273mg/kg) and tyramine (up to 131mg/kg), whereas Jajang samples had relatively small amounts of biogenic amines (mostly less than 40mg/kg). There appeared to be a strong relationship between biogenic amine contents in Chunjang and Jajang, and the biogenic amines in Chunjang were found to be pyrolysed during frying thereof to prepare Jajang. Meanwhile, the total plate counts of Chunjang samples ranged from 5 to 8logcfu/g, and most strains that were isolated from Chunjang samples were identified to be Bacillus subtilis (91.0%). The strains isolated from a sample in which relatively small amounts of biogenic amines were detected showed significantly weak abilities to produce biogenic amines. This indicates that biogenic amine contents in Chunjang are primarily attributed to bacterial abilities to produce biogenic amines.

Occurrence of biogenic amines in Miso, Japanese traditional fermented soybean paste.

The objective of this study was to analyze overall contents of biogenic amines in Miso and thereby evaluate the safety of the food. Through HPLC analysis of 22 different Miso products, it was found that most samples had low biogenic amine contents. However, some samples contained both histamine and tyramine close to hazardous levels of the amines, which indicate that the amounts of biogenic amines in Miso are not completely within the safe level for human health. Meanwhile, the biogenic amine contents showed no clear relationship with physicochemical parameters, whereas they revealed a good relationship with the ratio of soybean to other grains used in raw material. Thus, it turned out that biogenic amine contents in Miso are primarily affected by the ratio of raw ingredients, especially soybeans. The aerobic plate counts of Miso samples ranged from 3 to 8 Log CFU/g, and all the strains isolated from Miso samples were found to produce biogenic amines. Most strains were identified to be Bacillus subtilis, often regarded as the predominant contaminant bacteria in Miso, and highly capable of producing tyramine and spermine. Taken together, therefore, this study suggests that variability of biogenic amine contents in Miso are primarily attributed to the ratio of raw ingredients in the food that affects the relative contribution level of bacterial contaminants to the contents.

Occurrence of biogenic amines in Doubanjiang and Tofu

This study was performed to analyze biogenic amine contents and other parameters in doubanjiang and tofu. Through this study, it was found that doubanjiang contained considerably large amounts of most biogenic amines (>30 mg/kg of β-phenylethylamine in particular), and tofu had a relatively high level of spermidine (>20 mg/ kg). Therefore, the amounts of biogenic amines in the foods seem to be occasionally beyond the safe level for human consumption. Meanwhile, the biogenic amine contents in doubanjiang showed a good relationship with salt content (R2=0.89). The spermidine content in tofu samples was closely related to that in soybean, the raw material of tofu. There also appeared to be a good relationship (R2=0.82) between the biogenic amine contents and total plate counts in doubanjiang, but not in tofu. Most strains from the foods were capable of producing biogenic amines, and the identification revealed that bacterial ability to produce biogenic amines was determined at the level of strains rather than species. Taken together, it seems that biogenic amine contents in doubanjiang are mainly affected by fermentation processes, whereas those in tofu are primarily affected by raw materials.

Bacterial contribution to histamine and other biogenic amine content in Juk (Korean Traditional Congee) cooked with seafood

Eight representative types of juk (Korean traditional congee) cooked with seafood, and plain juk were analyzed for biogenic amine content. Results revealed that while plain juk contains no biogenic amines, juk prepared with seafood has a high level of histamine, ranging from 120 to 170 mg/kg. The seafood used in juk preparation contained different concentrations of histamine, ranging from 60 to 300 mg/kg. No other biogenic amines were detected in most juk and seafood samples. The bacterial contribution to the biogenic amine content in selected seafood was evaluated by analyzing the bacterial distribution and ability to produce biogenic amines. Strains of Achromobacter, Staphylococcus, and Micrococcus that are capable of producing biogenic amines are the dominant genera in the seafood tested. Therefore, this study suggests that the levels of dominant bacteria need to be controlled to reduce the amounts of biogenic amines in seafood and, thereby, in juk prepared with seafood.