3.5. Homogeneity and molecular weight
The elution profiles of apple, citrus and dragon fruit peel pectins as a function of elution volume obtained using HPSEC-MALLS-RI are illustrated in Fig. 4. RI gives a signal proportional to the concentration, whereas the MALLS response to a given concentration is proportional to the product: concentration molecular weight (Wyatt, 1993). The molecular characteristics of the pectins are shown in Table 4. The molecular weight (Mw) and chain length (Mn) of dragon fruit peel pectinwas found to be lower than that of apple and citrus pectins. Heterogenous profiles were observed, with dragon fruit peel pectin exhibiting a more pronounced sign of heterogeneity (Fig. 4c). A large polydispersity index (PDI) implies a
wider molecular weight distribution and the PDI is equal to 1 formonodispersive polymer (Rogosic, Mencer, & Gomzi, 1996). The larger PDI of dragon fruit peel pectin than that of apple and citrus pectins agreed well with the elution profile that is indicative of the higher heterogeneity of the sample