Abstract/Summary

Maltodextrins are polysaccharides that are widely used in the food industry due to their non-toxicity, low-price and functionality. Most polysaccharides are strongly hydrophilic and hence they are not suitable surface-active agents for emulsion systems. The modification of a polysaccharide’s hydrophilic nature through the introduction of an ester group results in the synthesis of an amphiphilic polysaccharide. This thesis explores the use of enzymatic transesterification reaction, which involves incubating maltodextrins of different dextrose equivalent (DE), namely DE 4-7, DE 13-17 and DE 16.5-19.5 with a vinyl laurate in a mixture of DSMO and tert-Butyl alcohol (10:90) as solvent, and using an immobilised lipase B from Candida antarctica (Novozym® 435) to catalyse the reactions. The highest degree of substitution (DS) was 0.43 and was observed with maltodextrin DE16.5, indicating that the DS is influenced by steric hindrances affecting the reactivity of hydroxyl groups. However, the maltodextrin DE16.5 laurate was obtained with the lowest conversion yield (6.6 mg/g of initial substrates) indicating that from a production perspective this would be a less economically viable process. All maltodextrin laurates showed to be surface-active at a concentration of 10, 20 and 40 % (w/v). The maltodextrin laurates were tested for their emulsion formation ability and emulsion stability, oil-in-water (O/W) emulsion food systems. The maltodextrin DE4 laurate showed good stabilising and emulsifying properties and was more effective than the rest in reducing the emulsion creaming rate, most likely due to its higher viscosity. In addition to their emulsification properties, it was hypothesised that maltodextrin laurates can act like low molecular weight surfactants with detergency properties. The stability and compatibility of the three maltodextrin laurates in detergent formulations was tested targeting the removal of lipophilic substances (rapeseed oil) from cotton cloth. All maltodextrin laurates were shown to possess the emulsion-stabilising capacity for vegetable oil, whereas the high emulsification index with rapeseed oil (54-66%) reflected good stability of the formed emulsion. High oil removal percentage (56-83%, w/w) was obtained under conditions of 0.1M Trizma buffer pH9 at 37 °C in all samples, whereas MDE4 laurate performed the best (83%, w/w) at a concentration of 1.0% (w/v) in the detergent formulation. Overall, the results of this study indicated that maltodextrin laurates have considerable potential in being used as emulsion stabilisers in foods and as surfactants in detergent formulations.