Locust Bean Gum

CAS Number: 9000-40-2

E Number: E410

Locust Bean Gum (LBG) is extracted from the seeds of Carob Tree. LBG, also known as carob gum, carob bean gum or carobin, is a galactomannan vegetable gum mostly found in Mediterranean region. The long pods that grow on the tree are used to make the gum. These long pods are cut to separate the seed from the pulp.

Generally, the Carob pod can be split into two fractions: pulp and seed. Carob pulp varies in properties depending on the harvesting time, cultivar and farming practices. However a basic analysis would be:

Component

%
Seed Coating 30-33
Endosperm 42-46
Embryo/Germ

23-25

 

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 contains polysaccharide which is then milled by a roller operation to produce the final locust bean gum powder.

Pulp can also be extracted to form sweet syrup that is popular as a drink in some countries. Carob pulp has also been used in fermentation processes to produce both proteins and alcohol.

Germ contains about 52% protein and the protein level in LBG is used as a quality indicator reflecting the efficiency of germ removal from the endosperm. The germ also contains about 8% lipids and 27% carbohydrate. High levels of the yellow germ in LBG powder causes the solutions to degrade faster due to polysaccharide degrading enzymes present.

Properties of Locust Bean Gum: 

  • The product, Locust bean gum, occurs as a white to yellow-white powder with a ‘typical’ odour and bland taste.
  • The product does not contain any husk.
  • Viscosity ranges from 2500 cps – 3000 cps.
  • The product does not boil, does not melt and does not burn.
  • It is dispersible in either hot or cold water which forms sol having a pH 5.4 – 7.0. It is partly soluble in cold water and needs heating in order to achieve it’s full viscosity. This can be converted into a gel by the addition of small amounts of sodium borate.
  • LBG is used as a thickening agent and gelling agent in food technology.
  • The viscosity of aqueous dispersions of locust bean gum increases very much on heating.
  • Quantitative coagulation experiments have been made and compared with those of many other hydrocolloids. The gelling with borax is explained as a cross-linking reaction.
  • Locust bean gum increases the gelling strength of agar gels. In a commercial enzyme preparation two “carubinases” which hydrolyze the two different glycosidic linkages of the polysaccharide have been found.
  • Locust bean gum can form derivatives. The reaction products of locust bean gum with acetic anhydride and with epichlorohydrin were especially studied.