Rheological and Structural Properties of High‐methoxyl Esterified, Low‐methoxyl Esterified and Low‐methoxyl Amidated Pectin Gels

Pectins are polygalacturonic acids with varying degrees of methyl esterification and are widely used to create gels. The commercial pectins studied by the authors were high‐methoxyl esterified pectin, low‐methoxyl esterified pectin and low‐methoxyl amidated pectin. A puncture test was performed at 5 and 20C using a texture analyzer. The compression force was recorded as a function of displacement. The resulting force‐displacement measurements were converted to stress‐strain to calculate Young's modulus by assuming incompressibility of the materials in a linear viscoelastic region (LVR). A rheometer was used for the shear flow curve, frequency sweep, amplitude sweep and creep tests, at 5 and 20C. The effects of temperature on storage and loss moduli were obtained. Further to that, a differential scanning calorimeter was used to investigate the melting behavior of pectin gels. The shear elastic moduli of pectin gels in an LVR were compared with Young's modulus. PRACTICAL APPLICATIONS Understanding the rheological properties of high‐methoxyl esterified pectin (HM), low‐methoxyl esterified pectin (LM) and low‐methoxyl amidated pectin (LMA) pectin gels is useful in the food, pharmaceutical and cosmetic industries for the improvement of product quality. The results may be used to model the relationship between the microstructural and mechanical properties of HM, LM and LMA pectin gels.