Raw material and Production

The carob tree
The carob tree, Ceratonia siliqua L., is a medium sized leguminous, evergreen tree with a well developed round crown and a short trunk. The tree is native widespread in the Mediterranean countries. Carob trees grow in their habitat usually in association with wild olives or pistachios, but carob plantations are also found. The trees grow best in calcareous soils, preferably near to the sea; they are drought resistant but tolerate only slight frost.

The quantity of carob bean kernels per pod depends on the variety and amounts to 8-15%.

The carob bean and its products
The fruit of the carob tree, the carob pod, is a chocolate brown and slightly bent pod when ripe and ready for harvest (late August to early October). Each pod bears 10 to 15 dark brown, hard seeds or kernels which are rather uniform in weight (ca. 0.2g). Arab jewellers used the kernels as weight unit to weigh precious metals and diamonds (hence the word “carat”). Carob kernels are the most valuable components of the carob bean because they are the starting material for the manufacture of carob bean gum.

The carob kernels are surrounded by a pulp (pericarp) which dries out to a brown mass during ripening. The pods are broken (“kibbling”) to small pieces (“kibbles”) thereby releasing the kernels which are separated. The kernels represent roughly 10% of the weight of the pod, the remaining 90% being the carob pulp.

Product of the Carob Beans are:

  • Carob Bean Gum (Locust Bean Gum) E 410
  • Carob germ meal
  • Kibbled carob and Carob Powder

Production of carob bean gum (CBG/LBG)

Carob kernels
The most valuable parts of the carob fruit are the kernels. Undoubtedly the endosperm is the most valuable part of the kernel which is ground to a fine powder and known commercially as “Carob Bean Gum” (CBG), syn. “Locust Bean Gum” (LBG).

Cross section of carob kernel (Neukom, H., Lebensm.-Wiss.u.Technol. 22, 41-45 (1989)

Production of carob bean gum
The carob kernels are difficult to process, since the seed coat is very tough and hard. By special processes the kernels are pealed without damaging the endosperm and the germ. The following procedures are applied:

Acid process:

The kernels are treated with sulphuric acid at a certain temperature to carbonise the seed coat. The remaining fragments of the seed coat are removed from the clean endosperm “sandwich” in an efficient washing and brushing process The sandwiches are dried and cracked and the more friable germs get crushed. The germ parts can be sifted off from the unbroken endosperm halves.

Roasting process:

The kernels are roasted in a rotating furnace where the seed coat more or less pops off from the rest. The germ and the endosperm halves are recovered as mentioned above. This process yields a product of somewhat darker colour. The advantage is that no sulphuric acid as processing aid is necessary, and, therefore, no effluent originates from the production process.

A coarse processing flowchart for Locust bean gum is as follow: