Effects of high hydrostatic pressure and thermal treatment on texture properties of pickled kohlrabi

The effects of high hydrostatic pressure (HHP, 400 MPa for 20 and 30 min) and thermal treatment (90 degrees C for 15 and 30 min) on the texture of pickled kohlrabi and their mechanisms were evaluated by in situ method, including low-field nuclear magnetic resonance, immunofluorescence, transmission electron microscopy, etc. Results showed that HHP could better maintain pickled kohlrabi texture than thermal treatment, with the samples showing higher hardness, springiness, moisture content, lower moisture freedom, and more uniform moisture distribution. Moreover, HHP significantly decreased the degree of esterification of pickled kohlrabi pectin, indicating the potential effectivity for Ca2+-based texture keeping additive. HHP caused no further damage on kohlrabi microstructure or pectin chain. However, damage of microstructure and loss of moisture significantly contributed to the texture loss of thermal-treated pickled kohlrabi, which revealed the necessity for microstructure protection and water holding during thermal processing to maintain pickled kohlrabi texture. These researches could provide guidance for better maintaining the texture of pickled vegetables during HHP and thermal processing.