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Isolation of Hafnia species from kimchi
1School of Food Technology and Food Service Industry, Yeungnam University, Gyeongsangbuk-do, Korea.
Abstract:
Eight commercially packaged kimchi products were examined over 15 days of storage at 4 degrees to evaluate the occurrence of Hafnia alvei (H. alvei). Additionally, 7 saeujeot products, as a possible ingredient source, were analyzed to examine the bacteria's origin. Over the storage period, kimchi samples had decreasing pH levels, which stabilized at pH 4.2; acidity increased to 0.9+/-0.1%. Lactose-nonfermenting bacteria, which H. alvei belongs to, gradually reduced in numbers over the kimchi storage. However, the relative frequency of H. alvei to lactose-nonfermenting bacteria tended to increase. From the kimchi samples, 58 H. alvei-presumptive colonies were selected. Forty-three colonies turned out to be H. alvei and 15 colonies were identified as other strains or of uncertain identification when the API 20E system was used. From further test, 3 of the 43 colonies were H. alvei (-) against the phage test. Finally, H. alvei was isolated from saeujeot, indicating that this ingredient can be an originating source of H. alvei in kimchi.
Insights
Hafnia alvei (H. alvei) occurrence in kimchi was studied. Researchers found that while H. alvei numbers decreased, its relative frequency increased, with saeujeot identified as a potential source.
Area of Science:
- Food microbiology
- Fermentation science
- Bacterial ecology
Background:
- Hafnia alvei (H. alvei) is a bacterium found in various environments, including fermented foods.
- Understanding the dynamics of H. alvei in kimchi is crucial for food safety and quality.
- Saeujeot, a salted fermented shrimp, is a common ingredient in kimchi and a potential source of microbial contamination.
Purpose of the Study:
- To investigate the occurrence and prevalence of Hafnia alvei (H. alvei) in commercially packaged kimchi during storage.
- To determine the potential origin of H. alvei in kimchi by analyzing saeujeot samples.
Main Methods:
- Kimchi samples were stored at 4°C for 15 days, with pH and acidity monitored.
- Bacterial populations, including lactose-nonfermenting bacteria and H. alvei, were quantified.
- API 20E system and phage testing were used for bacterial identification.
Main Results:
- Kimchi pH decreased and acidity increased during storage.
- The total count of lactose-nonfermenting bacteria decreased, but the relative frequency of H. alvei increased.
- H. alvei was successfully isolated from saeujeot samples, indicating it as a potential source.
Conclusions:
- Saeujeot can be an originating source of Hafnia alvei (H. alvei) in kimchi.
- The increased relative frequency of H. alvei in kimchi during storage warrants further investigation.
- Controlling H. alvei in kimchi may involve managing its presence in key ingredients like saeujeot.
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