High methoxyl pectin enhances the expansion characteristics of the cornstarch relative to the low methoxyl pectin

The addition of dietary fiber pectin in extruded foods is beneficial for human health. However, pectins with different methyl ester levels may have different effects on the quality of extrudates. Hence, in this study, low and high methoxyl pectin were extruded with corn starch to investigate their impact on the expansion characteristics of corn starch. Pasting and thermal properties of the blends and structural characteristics and physical properties of extrudates were evaluated. Pectin interacted with starch molecules and restricted water adsorption into amorphous regions of corn starch, which influenced the gelatinization. Low methoxyl pectin increased the viscosity of the blends from 718.0 +/- 8.7 to 773.0 +/- 9.5 mPa.s, but high methoxyl pectin showed the opposite effect (from 718.0 +/- 8.7 to 664.3 +/- 4.7 mPa s). The extrudates of high methoxyl pectin and corn starch blends showed better quality than that of low methoxyl pectin and corn starch blends, especially on the expansion ratio (3.76 +/- 0.01 for 15% HMP addition and 2.85 +/- 0.04 for 15% LMP addition). The results of this work demonstrated that high methoxyl pectin addition, even at high levels, had little effect on the quality of corn starch extrudates compared to the one without pectin addition.