Molecular differences of low methoxy pectins induced by pectin methyl esterase I: Effects on texture, release and perception of aroma in gel systems

Six types of low methoxy pectins (two commercial and four modified pectins treated with pectin methyl esterase from Valencia orange) with different degrees of esterification (DE), molecular weights (MW), and degrees of amidation were prepared. Pectin gels containing five aroma compounds were produced and their texture properties, release of aromas, and sensory flavour intensities were investigated. Regarding the gels made with lower MW pectins (<2.1 × 10⁵), only headspace concentration of isoamyl acetate was increased, according to the de-esterification of the pectins. In the pectin gels of higher MW (>3.7 × 10⁵), however, significantly higher concentrations of aromas in the headspace were shown in the gel with DE value of 6 than the gel with DE value of 40. Perceived flavour intensity was highest in the pectin gel with higher DE (∼40) and lower MW. The sensory texture analysis indicated that the pectin methyl esterase-modified pectin gels had increased hardness, coarseness of mass, springiness, and chewiness. The perceived flavour intensities of the gels showed strong negative correlations with firmness.