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This study aimed to assess the effects of three different freezing techniques — cold room freezing (CRF; −20 °C), air-blast freezing (ABF; −70 °C), and cryogenic immersion freezing (CIF; −70 °C) — on the microstructure and physicochemical properties of Korean white kimchi (KWK) during frozen storage at −20 °C and − 45 °C for 8 weeks. CIF-treated KWK exhibited a higher freezing rate and after ultra-cold (UC; −45 °C) frozen storage, it showed a greater number and smaller diameter and area of ice crystals than CRF- and ABF-treated KWK. Drip loss was reduced and CIE color changes were delayed in KWK under UC frozen storage. The pH, titratable acidity, and reducing sugar content of frozen KWK remained unaffected by the freezing method, storage temperature, or duration. Thus, CIF combined with UC frozen storage preserves the physicochemical quality of KWK with minimal histological damage during long-term storage. In the kimchi industry, where the shelf life of commercial products is often constrained by successive fermentation under low-temperature storage and distribution conditions, introducing frozen kimchi is a promising solution to reduce waste of overripe kimchi in the supply chain. This study highlights the effectiveness of combining CIF and UC frozen storage methods to minimize the damage caused by freezing in kimchi. This innovative technology provides a practical means for streamlining freezing processes, saving operational time, and ensuring kimchi quality during long-term storage and distribution.
Kang et al. (Mon,) studied this question.