Study on the ice crystals growth under pectin gels with different crosslinking strengths by modulating the degree of amidation in HG domain

The ice crystal morphology formed under a series of amidated pectin gels with various crosslink strengths were investigated. The results showed that as the degree of amidation (DA) increased, pectin chains exhibited shorter homogalacturonan (HG) regions. Highly amidated pectin exhibited a faster gelation rate and a stronger gel micro-network via hydrogen bonds. Based on cryogenic scanning electron microscopy (cryo-SEM), smaller ice crystals were formed in frozen gel with low DA, suggesting that a weaker cross-linked gel micro-network was more effective at inhibiting crystallization. After sublimation, lyophilized gel scaffolds with high crosslink strength displayed less number of pores, high porosity, lower specific surface area, and greater mechanical strength. This study is expected to confirm that the microstructure and mechanical properties of freeze-dried pectin porous materials could be regulated by changing the crosslink strength of pectin chains, which is achieved by increasing the degree of amidation in the HG domains.

Automated summary

The morphology of ice crystals in amidated pectin gels with different crosslink strengths was investigated. Increasing the degree of amidation resulted in shorter homogalacturonan regions in pectin chains. Highly amidated pectin formed a faster gelation rate and a stronger gel micro-network through hydrogen bonds. Lower degree of amidation led to the formation of smaller ice crystals in frozen gels, indicating that a weaker cross-linked gel micro-network effectively inhibited crystallization. Lyophilized gel scaffolds with high crosslink strength displayed fewer pores, high porosity, lower specific surface area, and greater mechanical strength after sublimation. The study suggests that the microstructure and mechanical properties of freeze-dried pectin porous materials can be controlled by adjusting the crosslink strength of pectin chains through amidation in the homogalacturonan regions.