Department of Agricultural Engineering, National Institute of Agricultural Sciences, RDA, Jeonju, Jeollabuk-do, 54875, Korea.
Protected Horticulture Research Institute, National Institute of Horticultural and Herbal Science, RDA, Haman, Gyeongsangnam-do, 52054, Korea.
J Food Sci. 2021 Mar;86(3):749-761. doi: 10.1111/1750-3841.15633. Epub 2021 Feb 18.
The supercooling degree (SD), which refers to the difference between the ice nucleation temperature and freezing point of kimchi, varies depending on the type of kimchi, manufacturer, recipe, and manufacturing season. The aim of this study is to investigate the major influencing factors for the supercooled storage of kimchi and to analyze the possibility of supercooled storage for commercial kimchi. Pearson correlation analysis determined that, in commercial kimchi manufactured between March and July 2018, the SD of kimchi correlated to the number of aerobic bacteria (P < 0.01), however, was not associated with lactic acid bacteria. Moreover, the ice nucleation temperature of saline solution inoculated with aerobic bacteria was reduced from -3.03 ± 0.04 to -6.18 ± 0.11 °C by 10 kGy gamma ray sterilization. Meanwhile, the ice nucleation temperatures of 1.8 kg of commercial red cabbage kimchi and 500 g of white cabbage kimchi manufactured in February 2020 were -3.93 ± 0.06 °C and -3.57 ± 0.06 °C, respectively, and they could be stored at -2.5 °C for 12 weeks without freezing. Additionally, supercooled storage of kimchi at -2.5 °C caused a fermentation delay effect compared to control storage at 1 °C, considering the acidity and amount of lactic acid bacteria. Therefore, if the number of aerobic bacteria is controlled during the manufacturing process of kimchi, supercooled storage at temperatures below -2.5 °C may extend the shelf life of kimchi. PRACTICAL APPLICATION: We have shown that aerobic bacteria are the key influencing factor for ice nucleation of kimchi during supercooled storage. Aside from the initial sterilization process, fermentation of kimchi can also be delayed by lowering the storage temperature below -2.5 °C. Moreover, the method of direct cool refrigeration may have an industrial-level application.
过冷度（SD）是指泡菜的成核温度与冰点之间的差异，它取决于泡菜的类型、制造商、配方和制作季节。本研究旨在探讨影响泡菜过冷储存的主要因素，并分析商业泡菜过冷储存的可能性。Pearson 相关分析确定，在 2018 年 3 月至 7 月期间生产的商业泡菜中，泡菜的 SD 与需氧菌数量呈正相关（P < 0.01），但与乳酸菌无关。此外，用 10 kGy 伽马射线灭菌可使接种需氧菌的盐水溶液的成核温度从-3.03±0.04°C 降低至-6.18±0.11°C。同时，2020 年 2 月生产的 1.8 公斤红甘蓝泡菜和 500 克白菜泡菜的冰核温度分别为-3.93±0.06°C 和-3.57±0.06°C，可在-2.5°C 下储存 12 周而不冻结。此外，与在 1°C 下进行对照储存相比，将泡菜在-2.5°C 下进行过冷储存会导致发酵延迟，这主要是考虑到酸度和乳酸菌的数量。因此，如果在泡菜的生产过程中控制需氧菌的数量，那么在低于-2.5°C 的温度下进行过冷储存可能会延长泡菜的保质期。实际应用：我们已经证明，在泡菜过冷储存过程中，需氧菌是影响冰核形成的关键因素。除了初始的灭菌过程外，通过将储存温度降低到-2.5°C 以下，也可以延迟泡菜的发酵。此外，直接冷却制冷的方法可能具有工业应用水平。
