Rapid enzymatic assay of biogenic amines in Doenjang and Gochujang using amine oxidase

Safety Analysis of Korean Cottage Industries' Doenjang, a Traditional Fermented Soybean Product: A Special Reference to Biogenic Amines

The typical Korean diet contains a significant quantity of doenjang owing to its unique taste and health benefits. However, the presence of anti-nutritional and toxic substances, such as biogenic amines and microbial pathogens, in doenjang has resulted in a loss of revenue and poor consumer health. The present study focused on the identification and quantification of different biogenic amines, pathogenic Bacillus cereus, and yeast counts in 36 doenjang products (designated as De-1 to De-36, 500 g each) procured from the different cottage industries situated in different parts of the Republic of Korea. The results indicated, only three samples were contaminated with B. cereus, exceeding the recommended limit (4 log CFU/g) suggested by the national standards of Korea. A total of six distinct yeasts were identified in different doenjang samples, whose comprehensive enzymatic profiling suggested the absence of harmful enzymes such as N-acetyl-β-glucosaminidase, α-chymotrypsin, and β-glucuronidase. The biogenic amines were detected in the range of 67.68 mg/kg to 2556.68 mg/kg and classified into six major groups based on hierarchical cluster analysis. All doenjang samples contained tryptamine, putrescine, cadaverine, histamine, and tyramine, while 94.44% were positive for spermidine and spermine. The results documented the analysis of traditional cottage industry doenjang and suggest the need for constant monitoring to ensure the safety of food for the consumer.

Evaluation of the biogenic amines in low-salt shrimp paste cooked under various conditions

Shrimp paste, a type of traditional Chinese food prepared from shrimp fermented with salt, contains biogenic amines (BAs). In this study, the BA content, salinity, and pH of eight commercial low-salt shrimp pastes were analyzed. In addition, the influences of various cooking conditions on the BA content of it were evaluated by HPLC. The total BA amount per product ranged between 32.39 and 1051.16 mg/kg. The salinity and pH were found significantly inversely correlated with the total BA amount. Of the cooking methods tested, after microwave heating and stir-frying, the total BA amount of shrimp paste, which showed the highest BA amount among 8 samples, declined from 1051.16 to 598.48 and 650.49 mg/kg, respectively; however, boiling or steaming showed no significant effects on the total BA amount. These results indicated possible health risk of low-salt shrimp paste whereas the risk could be reduced by choosing appropriate cooking method.

Quantification of Biogenic Amines in 35 Korean Cottage Industry Traditional Gochujang (Fermented Red Pepper Paste) Products

Traditional gochujang is well known for its distinguished flavor and taste. However, the safety of cottage industry gochujang products is uncertain, particularly, in terms of biogenic amine (BA) content which is not yet documented. The present study aimed to determine the level of BAs present in 35 traditional gochujang products nationwide. All gochujang products had considerable amounts of total BAs ranging from 52.95 mg/kg to 176.24 mg/kg. Individually, histamine and tyramine were either not detected or detected up to 16.94 mg/kg and 2.15–52.34 mg/kg, respectively. In all the tested gochujang products, putrescine, spermidine, and spermine were detected in the range of 7.60–56.72 mg/kg, 14.96–36.93 mg/kg, and 4.68–16.31 mg/kg, respectively. A total of 22 and 19 gochujang products had less than 1 mg/kg of cadaverine and histamine, respectively. The findings indicate that all the gochujang products tested herein had BA levels below the suggested toxicity limits recommended by the various regulatory authorities, which reveal that they are safe for human consumption.

Development of a colorimetric enzymatic assay method for aromatic biogenic monoamine-producing decarboxylases

Biogenic amines (BAs) produced by the action of bacterial amino acid decarboxylases in fermented foods cause various health problems in human. Despite the importance, detailed characterizations of the BA-producing decarboxylases are relatively less progressed than the studies on BA-producing bacteria, due to the time-consuming chromatography-based assay method. In this study, a simple and general colorimetric assay for aromatic amino acid decarboxylases coupled with an amine oxidase from Arthrobacter aurescens (AMAO) and horseradish peroxidase was developed using a tyrosine decarboxylase from Enterococcus faecium DSM20477 (EfmTDC) as a model enzyme. The activity profiles over pH and temperature and the kinetic analysis for EfmTDC revealed that the results by the colorimetric assay are compatible with those by the chromatographic assay. In addition, due to the broad substrate specificity of AMAO for histamine and 2-phenylethylamine, the colorimetric assay would be applicable to the characterization of other aromatic amino acid decarboxylases including histidine decarboxylases.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10068-021-00938-4.

Combined Cross-Linked Enzyme Aggregates of Monoamine Oxidase and Putrescine Oxidase as a Bifunctional Biocatalyst for Determination of Biogenic Amines in Foods

In order to determine total biogenic amines in fermented foods, the combined cross-linked enzyme aggregates of a monoamine oxidase and a putrescine oxidase (combi-CLEAs) and the cross-linked enzyme aggregates (CLEAs) of the fused enzyme of two amine oxidases (MonoAmine Putrescien Oxidase, MAPO) were prepared. The effects of various parameters were examined to optimize the CLEAs formation. Biochemical characterization and stability of free and the CLEAs enzymes were performed. Through optimization of the CLEAs formation condition, the combi-CLEAs and the CLEAs-MAPO were prepared with 82% and 78% of residual activities relative to the activities of the subjected enzymes were in a preparative scale. The optimal pH for tyramine-activities of the CLEAs enzymes were shifted to relatively basic pH, leading to synchronization of the optimal performances of combi-CLEAs over pH for tyramine and putrescine. In addition, thermostability of the CLEAs enzymes were improved with almost double half-lives at 65 °C in comparison to the free enzymes. The catalytic efficiencies of combi-CLEAs for tyramine, histamine and putrescine were reduced by 41%, 56%, and 31%, respectively, and the inhibition potency by the substrate was reduced by two-fold in comparison of the mixed free enzymes. In conclusion, combi-CLEAs are a promising catalyst with the improved stability and the same optimum pH for dual activities in enzymatic determination of biogenic amines in foods.

Occurrence and reduction of biogenic amines in traditional Asian fermented soybean foods: A review

Biogenic amines are harmful substances generated during the fermentation process. Regulations on biogenic amine content in fermented foods are currently insufficient in comparison to the popularity of fermented food consumption in Asian countries. The current review evaluated the biogenic amine content of fermented soybean-based Asian foods to determine whether the food products are safe for consumption. Though the reported ranges of biogenic amine content in fermented soybean foods varied widely, most products contained biogenic amine concentrations at potentially hazardous levels. To ensure the safety of fermented soybean food products, further efforts are required in the improvement of the food manufacturing process, as well as the establishment of regulations on managing biogenic amine content.

Optimizing the preparation conditions and characterization of cross-linked enzyme aggregates of a monoamine oxidase

Monoamine oxidases are useful in determination of biogenic monoamines, particularly histamine and tyramine. In this study, cross-linked enzyme aggregates (CLEAs) technique was applied to improve the stability of a monoamine oxidase from Arthrobacter aurescens (AMAO). Under the optimized condition (50% of saturated ammonium sulfate, 5 mM glutaraldehyde, 2.0 mg/mL AMAO, 4 h-cross-linking at 25°C, pH 8.0), CLEAs-AMAO was recovered with a yield of 82% based on the subjected total enzyme activity. Both pH activity and stability at alkaline pHs of CLEAs-AMAO were significantly improved compared to those of the free enzyme, resulting in the shift of optimum pH to pH 8.0 and a broader pH profile. The half-life of the CLEAs at 65°C was elongated by 1.7-fold compared to that of the free enzyme, suggesting the thermal stability of AMAO was also improved by the CLEAs formation.

Construction of a bifunctional enzyme fusion for the combined determination of biogenic amines in foods

Biogenic amines (BAs) are a group of low-molecular-mass organic bases derived from free amino acids. Due to the undesirable effects of BAs on human health, amine oxidase-based detection methods for BAs in foods have been developed. Here, we developed a bifunctional enzyme fusion (MAPO) using a Cu(2+)-containing monoamine oxidase (AMAO2) and a flavin adenine dinucleotide-containing putrescine oxidase (APUO) from Arthrobacter aurescens. It was necessary to activate MAPO with supplementary Cu(2+) ions, leading to a 6- to 12-fold improvement in catalytic efficiency (kcat/KM) for monoamines. The optimal temperatures of Cu(2+)-activated MAPO (cMAPO) for both tyramine and putrescine were 50 °C, and the optimal pH values for tyramine and putrescine were pH 7.0 and pH 8.0, respectively, consistent with those of AMAO2 and APUO, respectively. The cMAPO showed relative specific activities of 100, 99, 32, and 32 for 2-phenylethylamine, tyramine, histamine, and putrescine, respectively. The tyramine-equivalent BA contents of fermented soybean pastes by cMAPO were more than 90% of the total BA determined by HPLC. In conclusion, cMAPO is fully bifunctional toward biogenic monoamines and putrescine, allowing the combined determination of multiple BAs in foods. This colorimetric determination method could be useful for point-of-care testing to screen safety-guaranteed products prior to instrumental analyses.