Lubricating performance of pectin: Influence from the colloidal structures

This study demonstrates that the lubrication performance of pectin is markedly modulated by its colloidal structure. Motivated by the pH-altered lubricating performance of acidified pectin solutions, this work further investigates the lubricating properties of Ca 2+ -crosslinked pectin microgels (PMGs). The impact of Ca 2+ crosslinking on the physical and colloidal characteristics of PMGs suspensions is evaluated by visual appearance, microscopic morphology, and large amplitude oscillatory shear (LAOS) rheology analysis. Results show that only a low concentration of Ca 2+ (20–60 mmol/L) promotes the formation of a robust colloidal structure. The strain stiffening index (S) shows that Ca 2+ crosslinking endows pectin with greater resistance to applied strains, and notable strain stiffening behaviors are observed in PMGs suspensions. Friction curves suggest that acidified pectin solutions have lower maximum friction coefficients ( μ max ) and PMGs suspensions have narrower boundary regimes. Furthermore, the lubricating performance of PMGs suspensions can be regulated by the homogenization rate and NaCl concentration, where shorter boundary regimes are found in robust PMGs suspensions. For pectin-PMGs mixtures, friction curves further confirm that a low PMGs proportion (10 %) is sufficient to promote the rapid lubrication regime transition. By clarifying the linkage between colloidal structure and lubricating performance of pectin, this study provides new perspectives for regulating oral lubricating behavior in food products.