Extraction and characterization of pectin from coffee waste and the effects on pectin-maize starch gel

The pectin from coffee waste water and coffee pulp by different extraction methods were obtained and the interaction between pectin and maize starch (MS) were investigated in the present study. Degrees of methyl-esterification (DM) for pectin with acid (AEP), chelating agent (CSP) and water soluble pectin (WSP) were 45.8%, 22.6% and 28.6%, respectively. The results of pasting properties showed that pectin from coffee waste (CW) reduced the viscosity of composite gels, and ability of the pectin to maintain the viscoelasticity of composite gels followed the order AEP, CSP and WSP. The AEP, CSP and WSP significantly decreased the relative crystallinity from 4.03% to 2.91%, 1.37%, 3.10% and enhanced the short-range order. These results suggested that both methylation and RG-I are likely to interact with MS chains and the interaction mainly depended on hydrogen bonds without changing the B-type of crystallinity in the composite gels.