Carob and Locust bean gum – LBG properties

LBG properties

LBG comes in a variety of forms, basically as high, industrial and technical grades (Wielinga, 1989). For those buying LBG the key parameters to be aware of are:

1. Acid insoluble residues gives an indication of how well the skin has been removed from the seed. Hence the lower the acid insolubles the better.
2. Protein gives an idea of how well the germ has been separated from the endosperm. Hence the lower the protein level the better.

LBG is only partially soluble in cold water. The mannan sections of the polymer chain can bind together to form a crystalline region which is thermodynamically more stable than the solution state. Hence even when in solution at ambient temperature there is a tendency for the polymer chains to wish to aggregate. This makes the accurate measurement of molecular weight difficult due to the presence of aggregated species in solution. However it also has some advantages. The aggregation can be increased by reductions in water activity and reduction in solution temperature which ultimately forms a 3D network and a gel. This is exactly what happens in ice cream during freezing. There are two great advantages of this: firstly a weak gel structure does not impart a slimy or slippery mouth feel to the ice cream and more critically the formation of a weak gel on cooling imparts excellent meltdown resistance to the ice cream.

The synergy of LBG with kappa carrageenan is the basis of the majority of non gelatin dessert jellies as well as most of the jelly used in canned pet foods. The texture of a LBG/carrageenan gel can be manipulated to be close to gelatin and the higher melting temperature is a positive advantage in warmer countries or countries where refrigeration is not present in every household. It is also known that the melting point of the synergistic gel can be manipulated by altering the molecular weight of the LBG. This probably has more use in terms of aiding processing than it actually does in terms of providing a melt in the mouth sensation.

There have been several patents and articles covering different ways to manufacture or mimic LBG from a different source. The only method known to have been commercialised is the treatment of guar with an alpha-galactosidase enzyme to produce a galactose depleted guar with properties similar to LBG.

Additional information on Carob & LBG structure, production and properties can be accessed using the arrows in the Further Reading box below.