The crude and purified locust bean gum (LBG) from seven areas of the north and centre of Tunisia (Bouarada, Bargou, Kessra, Haffouz, Borj Toumi, Ben Arous and INRGREF) were analyzed for moisture, ash, protein, acid-insoluble matter and mannose/galactose ratio. The purified samples exhibited higher mannose/galactose ratios and lower amounts of ash, protein and acid-insoluble matter than the crude gum. The purified LBG from different regions had 3.43–6.99% moisture, 0.87–2.06% ash, 0.61–2.46% protein, 0.00–1.20% acid-insoluble matter and 3.55–4.32 mannose/galactose ratios. Statistical analysis revealed that purification significantly affected (P < 0.05) moisture, ash, protein, insoluble matter contents and mannose/galactose ratios of the crude LBG and purified LBG for all samples from different areas. The rheological properties of the different carob gum samples were determined, the best rheological properties are those of spontaneous carob trees of Bargou, Bouarada and Kessra areas. The climatic and geographic origin of carob and the cultivation mode influence the chemical and rheological properties. The purification of crude galactomannan samples by precipitation with isopropanol gave a clear and more stable solution, due to the elimination of impurities and endogenous enzymes.