4. Strategies to Reduce Biogenic Amine Content in Kimchi Products
Despite the risks associated with BA accumulation, limited research has been conducted on reducing the BA content of kimchi products. Instead of directly reducing BA content in kimchi, several studies have reported various methods to reduce BA concentrations in the kimchi ingredients
Jeotgal and
Aekjeot. Kim et al.
[39] reported that kimchi produced using fermented seafood products contained BA at significantly higher concentrations. Lee et al.
[40] suggested that the BA concentration of kimchi products may be reduced by limiting the quantity of the fermented seafood products used during kimchi production. For example, Kang
[41] reported the histamine content of kimchi without
Myeolchi-
aekjeot at safe levels, however, the addition of
Myeolchi-
aekjeot raised histamine content to unsafe concentrations above the recommended limit by a factor of approximately 6. The study also described the effect of heat treatment of
Myeolchi-
aekjeot on the histamine content of kimchi. Histamine concentrations in kimchi produced using heat-treated
Myeolchi-
aekjeot were reported at 546.14 ± 1.33 mg/kg, while non-treated kimchi contained 592.78 ± 3.43 mg/kg. The reported results indicate that microorganisms from
Myeolchi-
aekjeot contributed towards the production of histamine during kimchi fermentation. Also, as research shows that histamine is heat-stable
[42], the lower BA content in kimchi produced using the heat-treated
Myeolchi-
aekjeot may be due to the sterilization of histamine-producing microorganisms
[41]. In addition to the contribution of BA content in kimchi by
Myeolchi-
aekjeot, Lee et al.
[31] suggested that microorganisms from
Myeolchi-
aekjeot may produce BA during kimchi fermentation. Utilizing substitute ingredients in lieu of
Myeolchi-
aekjeot and
Kkanari-
aekjeot may also be effective in reducing BA content in kimchi. As other
Jeotgal products including
Ojingeo-
jeot (salted and fermented sliced squid),
Toha-
jeot (salted and fermented
toha shrimp),
Jogae-
jeot (salted and fermented clam),
Baendaengi-
jeot (salted and fermented big-eyed herring), and
Eorigul-
jeot (salted and fermented oysters) have been found to contain individual BA content below 100 mg/kg
[43], utilization of the fermented seafood products with low BA content for kimchi production is expected to reduce the overall BA content of kimchi products
[29].
Research on using additives to reduce the BA content of fermented seafood products has also been reported. Mah et al.
[44] conducted research to reduce BA production by microorganisms isolated from
Myeolchi-
jeot, introducing additives into assay media and
Myeolchi-
jeot. The results confirmed that compared to the control, garlic extract was the most effective inhibitor of bacterial growth and BA production by yielding lower in vitro production of putrescine, cadaverine, histamine, tyramine, and spermidine by 11.2%, 18.4%, 11.7%, 30.9%, and 17.4%, respectively. Further results revealed that compared to
Myeolchi-
jeot samples treated with ethanol (control), the addition of 5% garlic extract to
Myeolchi-
jeot (treatment) inhibited bacterial growth and consequently reduced overall BA production by up to 8.7%. In another study by Mah and Hwang
[45], other additives were also used for the reduction of BA production by
Myeolchi-
jeot microorganisms in assay media and
Myeolchi-
jeot. Among the additives tested in assay media, glycine most effectively inhibited in vitro BA production by bacterial strains. In comparison to the control without additives, the addition of 10% glycine in assay media resulted in reductions in putrescine, cadaverine, histamine, tyramine, and spermidine production by 32.6%, 78.4%, 93.2%, 100.0%, and 100.0%, respectively. Compared to the
Myeolchi-
jeot samples salted at 20% NaCl, additional supplementation of 5% glycine reportedly reduced overall BA content by 73.4%. The results suggest that the addition of glycine as well as salt may improve the safety of fermented seafood products. It is noteworthy that despite the results showing effective BA reduction, the use of garlic extract or glycine may affect the flavor of the final product.
Aside from additives, other studies have utilized starter cultures to reduce BA content in
Jeotgal. In a study by Mah and Hwang
[46], some bacterial strains isolated from
Myeolchi-
jeot were found to reduce BA content in
Myeolchi-
jeot. The reported results showed that, of the 7 starter candidate strains,
S.
xylosus exhibited the highest histamine degradation capability as well as the ability to slightly degrade tyramine in assay media. In comparison to the uninoculated
Myeolchi-
jeot control, the addition of the starter culture reduced the production of putrescine, cadaverine, histamine, tyramine, and spermidine by 16.5%, 10.8%, 18.0%, 38.9%, and 45.6%, respectively. Jeong et al.
[47] isolated strains from
Jeotgal for use as potential starters and found that
S. equorum strain KS1039 did not produce putrescine, cadaverine, histamine, and tyramine in vitro.
A limited number of studies have even attempted to directly reduce the BA content of kimchi through the inoculation of bacterial strains. Kim et al.
[48] reported reductions in tryptamine, putrescine, cadaverine, histamine, and tyramine levels in
Baechu kimchi fortified with
Leu. carnosum,
Leu. mesenteroides,
Lb. plantarum, and
Lb. sakei strains. Similarly, Jin et al.
[30] reported that
Kkakdugi and
Chonggak kimchi inoculated with
Lb.
plantarum strains incapable of producing BA contained lower level of tyramine (but not the other BA) than the uninoculated control. Therefore, utilizing LAB strains unable to produce (and/or able to degrade) BA as kimchi starter cultures may likely reduce the total BA content during kimchi fermentation.
Although the aforementioned studies have shown both direct and indirect methods of reducing BA content in kimchi, current commercial kimchi production processes do not appear to utilize the BA reduction techniques. This might be due to the application of BA reduction methods such as the use of additives, starter cultures, and adjusting the quantity of fermented seafood products have been reported to affect the flavor of kimchi products
[45][49][50]. Consequently, inconsistent product quality is reflected in the wide range of BA content of kimchi products, including concentrations that exceed recommended limits for safe consumption. The high BA content reported for various kimchi products indicates that modern production methods require further preventative measures to ensure the safety of the fermented vegetable products, including practical application of research-based BA reduction techniques described above. Commercial kimchi production may greatly benefit from utilizing the aforementioned and novel strategies including control of fermentation conditions, utilizing starter cultures, alternative ingredients, and/or ingredients with low BA content. Furthermore, the establishment and expansion of regulations limiting BA content in fermented foods remain necessary to safeguard consumers against the potential BA intoxication.