Kimchi’s composition at different fermenting temperatures

October 27, 2016

A study published in the Journal of Food Science evaluates the effect of fermentation temperature on the volatile composition of Kimchi—a traditional Korean fermented food.

It is known that the optimal fermentation temperature for superior aroma and flavor of Kimchi is 4°C–5°C because the temperature determines the distribution of fermentative microorganisms involved in fermentation. However, commercially manufactured Kimchi is usually fermented for a short period (1–2 days) at 20°C and then distributed at a low temperature (5°C–8°C). Therefore, it is important to know the changes in volatile composition in Kimchi fermented at different temperature conditions.

The researchers fermented Kimchi at two temperature conditions (4°C and 20°C) and analyzed the volatile compounds of the samples during the fermentation periods using the dynamic headspace gas chromatography-mass spectrometry method. They found that the optimum ripening time for the Kimchi fermented at 4°C was 35 days, while for Kimchi fermented at 20°C the optimal time was 2 days. The pH at the optimum ripening time was 4.97 and 4.41, and the titratable acidity was 0.59% and 0.76% for the Kimchi fermented at 4°C and 20°C, respectively.

The researchers identified 40 different types of volatile compounds, including alcohol, aldehyde, ester, and sulfur compounds. The Kimchi fermented at 20°C produced greater amounts of volatile compounds than that at 4°C. The amounts of most volatiles increased as the fermentation time increased, but those of aldehydes decreased rapidly during both 4°C and 20°C fermentation. Organic acids, ester, and nitriles were detected only in Kimchi fermented at 20°C. The amounts of dimethyl disulfide, methyl-2-propenyl disulfide, and di-2-propenyl disulfide produced from the Kimchi fermented at 20°C were more than two times of those at 4°C.

The researchers concluded that the strong pungent odor of Kimchi fermented at 20°C is probably due to the high amount of organic acids (low pH) and sulfur compounds (dimethyl disulfide, methyl-2-propenyl disulfide, and di-2-propenyl disulfide) produced at this higher temperature.