Effect of preharvest boron spraying on the firmness and microstructure of winter‐harvested frozen broccoli among maturity types

Abstract Background Softening of winter‐harvested frozen broccoli is a challenge. Application of boron (B) can improve fruit texture, but its effects on processed vegetables remain unexplored. This study is the first to investigate the impact of preharvest B spraying [0 (unsprayed), 195, 390, and 585 mg B L −1 ] on the firmness and microstructure of frozen broccoli, utilizing different cultivars harvested during the winter season. Result In the unsprayed group, ‘Pixel’ florets exhibited the highest firmness, followed by ‘Ohayo’, ‘Konnichiwa’, and ‘Kombanwa’, depending on the extent of low‐temperature exposure before harvest. Application of B did not enhance the firmness of ‘Pixel’ or ‘Ohayo’ florets after freeze–thawing, despite reducing water‐soluble pectin levels. Conversely, spraying with 585 mg B L −1 improved the firmness of freeze–thawed ‘Konnichiwa’ and ‘Kombanwa’ florets exposed to temperatures < 0 °C before harvesting by improving cell wall integrity via increased sodium carbonate (Na 2 CO 3 )‐soluble or chelator‐soluble pectin. Synchrotron X‐ray computed tomography analyses suggested the frozen state has a more ordered cell structure, whereas scanning electron microscopy revealed less cellular structure damage in the thawed state for ‘Konnichiwa’ florets sprayed with 585 mg B L −1 compared with unsprayed florets. Nevertheless, freeze–thawed ‘Konnichiwa’ and ‘Kombanwa’ florets sprayed with 585 mg B L −1 were considerably less firm than unsprayed ‘Pixel’ or ‘Ohayo’ florets. Conclusion Preharvest B spraying enhances the firmness of freeze–thawed broccoli grown at low temperatures by increasing cell wall rigidity and minimizing cell structure damage. Nonetheless, B application cannot fully overcome the consequences of exposure to low temperatures before harvest. © 2025 Society of Chemical Industry.