Locust Bean Gum
LBG, also known as carob gum and St. John's bread, it is a vegetable gum extracted from Carob pods of the Carob tree. It is found only around the Mediterranean Sea due to its sensitivity to low temperatures and has been used as a food source for thousands of years. The pods are kibbled to separate the seeds from the pulp. The seeds are deskinned, 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, then the endosperm is milled by a roller operation to produce the final Locust Bean Gum powder.
What is it ?
A fibrous carbohydrate from the galactomannans group and is a guar gum relative. It is a linear polysaccharide from a chain of sugars made up of a mannose backbone and galactose side groups, with a ratio of 4:1. Locust bean gum is less soluble and has a lower viscosity, than guar gum, as it has fewer galactose branchpoints. It needs to be heating to dissolve, but is soluble in hot water. Locust bean gum differs from guar gum in that it forms thermal-irreversible weak gels by association of the galactose deficient side groups and therefore, has poorer freeze-thaw stability. It is used as a thickening agent, a stabilizer, and has synergistic properties.
What do we use it for ?
One of the principal food uses of LBG is as an ice cream and sorbet stabilizer. It imparts a smooth melt-down and desirable freeze-thaw shock resistance to the ice cream. It also produces softer doughs with greater resiliency when baking, is used as a texture modifier in soft cheeses, and a binding and lubricating agent in sausages.
Kappa Carrageenan. Makes for stronger gels, less brittle, more cohesive, and less prone to synersis. Kappa-LBG mixes are strongest in ratio of 60-40, and can be used as a substitute for gelatin. Must be brought to a boil to become fully functional.
Xanthan Gum. To form elastic gels at a 1:1 ratio.
Agar Agar. Makes for less rigid and more elastic texture in ratio of 9 parts agar to 1 part LBG.
- Density is improved by mixing with 3-5 times its volume with sugar.
- For proper hydration, heat to least 90 degrees Celcius under high shear.
- Viscosity is high at a lower temperature.
- Freeze/thaw stable.
- Appearance is often hazy, but clear variety is now available(CP Kelco).
- Typical pH: down to 3.6 if boiled and lower if not over heated.
- Shows pseudoplastic, or "shear thinning" properties. Solutions do not possess a yield point.
0.5% to 1% and AgarLBG 1% to 1.5%
<u>Further Reading/Research:</u> Hydrocolloids: Practical Guides for the Food Industry (Eagan Press Handbook Series), Andrew C. Hoefler, Martin Chaplin: Locus bean gum, London South Bank University, web page.