Locust bean gum

Production

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. The deskinned seed is then split and gently milled. This causes the brittle germ to break up while not affecting the more robust endosperm. The two are separated by sieving. The separated endosperm can then be milled by a roller operation to produce the final locust bean gum powder.

Chemistry

Locust bean gum occurs as a white to yellow-white powder. It consists chiefly of high-molecular-weight hydrocolloidal polysaccharides, composed of galactose and mannose units combined through glycosidic linkages, which may be described chemically as galactomannan. It is dispersible in either hot or cold water, forming a sol having a pH between 5.4 and 7.0, which may be converted to a gel by the addition of small amounts of sodium borate.

Food science

The bean, when made into powder, is sweet—with a flavor similar to chocolate—and is used to sweeten foods and as a chocolate substitute, although this carob powder is produced from the fruit pod after removal of seeds, while the gum is produced from the seeds themselves. It is also used in pet foods and inedible products such as mining products, paper making, and to thicken textiles. It is used in cosmetics and to enhance the flavor of cigarettes. Shoe polish and insecticides also have locust bean gum powder as an additive. It is soluble in hot water.

In 2011, Spain was the largest source of imports into the United States accounting for about 60% by volume (roughly 1,800 tonnes). Italy (670 tonnes) and Morocco (400 tonnes) ranked second and third respectively. Virtually all consumption of locust bean gum is in the food industry.