Abstract: This study was conducted to investigate the effects of blanching methods and freezing rates on the textural properties of processed broccoli. Low-field nuclear magnetic resonance (LF-NMR) spectroscopy and physicochemical analysis were used to evaluate the water distribution, water-holding capacity (WHC), electrical conductivity, and hardness of broccoli samples subjected to hot water or steam blanching followed by freezing at −20, −40, and −80 ℃. Besides, the microstructure was observed. The results indicated that the optimal process for maintaining the hardness of broccoli was steam blanching followed by freezing at −40 ℃. The treatment group exhibited the greatest increase in the peak area proportion (A21) of bound water compared with the control group and the strongest water-holding capacity, the inflorescence and stem retaining 66.72% and 62.53% of the initial hardness, respectively, and the relative electrical conductivity increasing to 87.01%. Scanning electron microscopy (SEM) images showed that the integrity of the cellular structure was maintained after the treatment. This study provides theoretical and technical support for maintaining the quality of frozen prepared broccoli in actual production process.

Key words: prepared broccoli; water-holding capacity; moisture migration; texture