Preparation and characterization of low methoxyl pectin by high hydrostatic pressure-assisted enzymatic treatment compared with enzymatic method under atmospheric pressure

• HHP-assisted enzymatic method (E-HHP) for LMP production is proposed.
• The preparation conditions (pressure, temperature, time) of E-HHP were optimized.
• The properties of two pectins de-esterified by E-HHP and E-AP were compared.
• E-HHP-prepared pectin had higher viscosity and induced a more homogeneous gelation.
• E-HHP could be taken as a highly efficient and novel method for LMP preparation.

A commercial pectin was de-esterified by using the HHP-assisted enzymatic method (E-HHP), and the effects of pressure, temperature and pressure-holding time on the degree of esterification (DE) of pectin de-esterified by E-HHP were investigated. A single factor experiment and an orthogonal test were performed to optimize the de-esterification condition of E-HHP. The optimal conditions of E-HHP consisted of a pressure of 400 MPa, a temperature of 45 °C and a pressure-holding time of 15 min. Under the optimal conditions, the DE was decreased from 65.32 ± 0.64% to 28.08 ± 1.39% within 15 min, whereas 120 min was required to obtain pectin with a similar DE (26.64 ± 1.00%) using the enzymatic method under atmospheric pressure (E-AP). The physicochemical properties, rheological and gelling characteristics of pectin de-esterified by E-HHP and E-AP were also compared. The results showed that the pectin prepared by E-HHP had much higher viscosity and induced a rapid and homogeneous gelation, leading to the formation of gel with better viscoelastic properties, whereas the other characteristics showed no significant difference. E-HHP had no degradation action on the pectin molecule as demonstrated by the viscosity-average molecular weight and molecular weight distribution. From these results, it could be concluded that E-HHP is a highly efficient and novel method to prepare low methoxyl pectin.

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