Abstract
Locust bean gum (LBG) is mucilage from the seed endosperm of the carob tree (Ceratonia siliqua L.) containing galactomannan polysaccharides. This galactomannan was extracted from the milled seeds in hot water. The purification of this polysaccharide by precipitation with isopropanol drastically reduced ash and protein and thus an almost pure galactomannan is obtained. Purified gum has a wide variety of food and industrial applications due to its ability to give very viscous solutions at relatively low concentrations. The addition of this hydrocolloid at levels of 0, 0.25, 0.50 and 1g/100g (w/w) to ketchup processed from double concentrate of tomato paste dilution, having total soluble solid (TSS) content 12.5g/100g (w/w); and its effect on the rheological properties of tomato ketchup was investigated using a Rheomat RM-180 viscosimeter. Results showed a pseudoplastic behaviour, and that an increase in LBG concentration resulted in a change of the shear thinning properties of the ketchup samples as showed by determination of a flow index, consistency index and a variation of apparent viscosity vs. shear rate.