Effect of heat treatment and homogenization on the rheological properties of aqueous parsnip suspensions

Parsnip (Pastinaca sativa) suspensions, at concentrations corresponding to a dilute and concentrated regime, were subjected to pasteurization, and heat treatments that favored β-elimination reactions and pectin methyl esterase activity. The different heat treatments were combined with homogenization. Physicochemical properties such as content of insoluble/soluble material and insoluble/soluble pectin were measured together with particle and rheological properties. Pectin methyl esterase activity led to a high yield of insoluble material and insoluble pectin, whereas β-elimination led to a high yield of soluble material and solubilized pectin. Homogenization after heat treatment resulted in increased solubilization of the pectin, especially after β-elimination reactions. Parsnip suspensions subjected to pectin methyl esterase activity exhibited the highest elastic modulus most likely due to the cross-linked pectin conferring rigidity to the cell walls. The content of insoluble material and the particle properties such as size and rigidity are important factor for the rheological properties of concentrated parsnip suspensions.

► Pectin methyl esterase increases content of insoluble pectin in parsnip suspensions.
► β-Elimination increases content of soluble pectin in parsnip suspensions.
► Homogenization increases content of soluble pectin, especially after β-elimination.
► Suspensions subjected to pectin methyl esterase activity have the highest G′.
► Rheology of concentrated parsnip suspension is also governed by particle rigidity.