Pichia kudriavzevii is the major yeast involved in film-formation, off-odor production, and texture-softening in over-ripened Kimchi

Yeasts were isolated from over-ripened kimchi and identified. Isolates were identified as Pichia kudriavzevii, Kazachstania servazii, Kazachstania exigua, Kazachstania bulderi, and Rhodotorula mucilaginosa. Among the isolates, P. kudriavzevii GY1 and K. bulderi HY2 were separately inoculated into kimchi and incubated at 10°C for 21 days. After incubation, HY2 kimchi showed less offodors, whereas GY1 kimchi showed strong off- and moldyodors in the sensory evaluation. P. kudriavzevii GY1 showed significantly higher polygalacturonase activity than K. bulderi HY2. Volatile compounds in kimchi samples were analyzed by HSPM-GC. Peak areas of obnoxiousodor compounds, including methanethiol, were 6.61, 9.46, and 20.87% for control kimchi, HY2 kimchi, and GY1 kimchi, respectively. Therefore, P. kudriavzevii was mainly responsible for kimchi spoilage, including off-odors and texture softening. Moreover, K. bulderi was associated with kimchi deterioration at cell counts up to 8.0-9.0 log CFU/mL, even though its effects were not as strong as those of P. kudriavzevii.