Locust bean gum is a galactomannan vegetable gum extracted from the seeds of the carob tree, mostly found in the Mediterranean region.The long pods that grow on the tree are used to make this gum. The pods are kibbled to separate the seed from the pulp. The seeds have their skins removed by an acid treatment.ocust bean gum is a galactomannan vegetable gum extracted from the seeds of the carob tree, mostly found in the Mediterranean region.