Food grade carboxymethyl cellulose preparation from African star apple seed (Chrysophyllum albidum) shells: optimization and characterization

Abstract

α-cellulose isolated from African star apple seed shell (ASASS) was used as the raw material for the production of food-grade carboxymethyl cellulose (CMC). Preparation of CMC from ASASS cellulose was carried out by an etherification process, using sodium hydroxide and monochloroacetic acid (MCA) at various temperature. The cellulose and CMC were characterized by FTIR, XRD and SEM techniques. Degree of substitution (DS) was determined using potentiometric titration. Solubility increased with DS of CMC increased together with varied conditions but decreased at a certain level. The optimum results of varied conditions were 0.8015 DS for 30% NaOH concentrations; 0.6259 DS for 50℃ temperature and 0.9254 DS for the amount of MCA. The FTIR spectra revealed the functional group modification of native cellulose to CMC, with absorptions at  1409.49 cm^-1 and 1640.05 cm^-1 indicating ether and carboxyl functional group respectively. The results of XRD analysis showed that crystallinity of isolated cellulose decreased in the CMC and SEM showed the elongated long fibres in cellulose while the fibrils in CMC are short and rough. The obtained product is well suited for pharmaceutical and food additives.

Keywords: Food grade, carboxymethyl cellulose, cellulose, optimization, degree of substitution, characterization.