Carbamoylethyl locust bean gum: Synthesis, characterization and evaluation of its film forming potential

Abstract

The synthesis of carbamoylethyl locust bean gum (CLBG) was optimized using Plackett-Burman design. The generated model showed high significance (p < 0.05) to all the response variables which justifies the authenticity of the designed model. The optimal conditions i.e. acrylamide (5.12 mM), sodium hydroxide (3.00 mM), reaction temperature (50.97 °C) and reaction time (2.00 h) supported maximum -CONH2 content (5.44%), –COOH content (3.04%), degree of substitution (0.85) and product yield (7.25%, w/w). Carbamoylethylation of locust bean gum (LBG) involved substitution of its hydroxyl (-OH) moieties with amide group (-CH2CH2CONH2). FTIR and NMR spectroscopy confirmed the addition of amide group to CLBG. Scanning electron microscopy assured the slight rough surface of CLBG particles. Differential scanning calorimetry showed that carbamoylethylation of LBG lowered its melting temperature range (205.60–272.45 °C). However, the amorphous nature, non-Newtonian flow and shear-thinning behaviour of pure LBG were retained in CLBG. Further, CLBG films prepared with glycerol (1%, w/w, plasticizer) showed partially smooth surface and have clear transversal cross-sections. CLBG-glycerol films were highly water resistant and almost transparent. Further, CLBG-glycerol films showed good tensile strength (18.55 ± 0.02 MPa) and higher percentage elongation (6.11 ± 0.01%). Water vapor transmission rate of CLBG-glycerol film was quite lower (0.211 ± 0.001 g.mm/h.m2.kPa) which verified its higher resistance towards water.