A Gum Worth Its Weight in Gold

A Gum Worth Its Weight in Gold

By Donna Berry
Contributing Editor

Ifyou are unfamiliar with the origins of the highly functional, all-naturalthickener referred to as locust bean gum (LBG), sit back and enjoy. This is astory you want to know.

For starters, LBG is extracted from the seeds of carob pod, which grows onthe carob tree (Ceratonia siliqua), part of the pea family (Leguminosae),that has been highly valued by humans and animals for thousands of years.

Biblical scholars believe John the Baptist, later known as St. John,sustained himself in his desert life by eating carob pods. The belief is sowell-established that a common name for the carob tree is St. Johns Bread.John the Baptist is also the likely source of the name locust bean, as it isreported that he subsisted on locusts and wild honey. The locusts arebelieved to be the carob pods, not the insect, and they actually have a sweet,honey-like taste.

This is where theres some disconnect, for reasons unknown. There actuallyis a tree called the locust tree, Robinia pseudoacacia, a genus native tothe United States and Mexico that also belongs to the family Leguminosae.Its common name arose from its resemblance to the carob tree, which was known asthe locust tree in biblical times (again, heres that disconnect). Thisduplication of common names causes confusion, so botanists have given the twotrees their own unique scientific name; however, for some unexplained reasoned,the ingredient processed from the carob tree is usually referred to as locustbean gum.

The carob tree, an evergreen that can rise upward of 50 ft. above the ground,is native to the Mediterranean region. In addition to being consumed by thelikes of John the Baptist, the carob trees seeds, which are quite consistentin weight, were used as weights by early merchants to determine the value ofprecious gems and gold dust. The Greek word for the carob pod kerationbecamecarat and eventually karat. One carob seed, weighing about 200 mg,would be balanced by a one-karat diamond or ruby. The karat value for gold isstill used, not as a measure of weight, but of the amount of gold in an object.

A golden ingredient

For food formulators, the seed of the carob pod is worth its weightin gold, as the seed contains galactomannan, a carbohydrate used to thicken andstabilize a variety of products. The galactomannan is obtained from the pods,which can grow up to a foot in length. The pods dry on the tree and areharvested when they fall to the ground.

First, the whole, washed carob pod is kibbled, which is the term used todescribe breaking up the pods and separating the seeds from the pods. Kibblingis accomplished by a machine called, you guessed it, the kibbler, says PaulFlowerman, president, P.L. Thomas & Co., Morristown, NJ. It is kibbled toseparate the pod from the five to 15 seeds in each pod. When the seeds areremoved, the pod is kibbled to various grades for animal feed, and even morefinely to produce a very fine chocolate substitute appropriately named carob.

The real money for the carob-pod processor is in the seed. First, the tinyseeds have to be polished, a difficult process as the seed skins are very tough.This is accomplished by either a mechanical or acid process, or a combination ofthe two, says Flowerman. Once the seeds are split, they are milled, orground, and, using a sieve, the tiny plant embryo, or germ fragments, areseparated from the endosperm.

The endosperm is the source of the valuable carbohydrate galactomannan. Theendosperm is further processed to produce various grades of LBG. It is acompletely natural product with no chemical modification or additives, saysMar Nieto, TIC Gums Inc., Belcamp, MD. In addition, LBG is a source ofsoluble fiber.

Like guar, LBG is a galactomannan. The LBG molecule has about 3.5 mannoseunits for every galactose residue. This non-ionic molecule typically is made upof about 2,000 residues. The galactose residues prevent strong chaininteractions; but, as many as 11 unsubstituted mannose residues may line up in arow. Junction zones may form between such clear areas when there are more thansix unsubstituted residues. These nano-crystalline links only dissociate in hotwater. If the galactose residues were perfectly randomized or blocked, it islikely that each molecule would have more than four such areas capable of actingas junction zones, thus allowing cold-water gel formation.

Being a long-chain polysaccharide, LBG is capable of binding large amountsof water as it hydrates. Therefore, it affects the rheology of the aqueousmedium into which it is dispersed, says Joshua Brooks, vice president salesand marketing, Gum Technology Corporation, Tucson, AZ. Unlike guar or taragum, also both galactomannans, LBG requires heat in order to fully hydrate.Heating provides the additional energy required to activate the long-chainmolecules and allows these molecules to sweep through the surrounding watermolecules promoting hydration.

Nieto says, For complete hydration and maximum viscosity, LGB requiresheating to 180°F for two to five minutes. Viscosity after heating can be closeto 3,000 cps. In contrast, guar gum, a cold-water soluble gum, has a 1% usagelevel viscosity of about 3,500 cps without heating.

Because LBG only develops viscosity after heating, it is readily dispersiblein aqueous systems without excessive viscosity build up. Being non-ionic, LBG isnot affected by ionic strength or pH, but will degrade at pH extremes at highertemperatures.

LBG is pseudoplastic, or shear-thinning. When fully activated, on its ownLBG will form a pseudo gel, like a hair gel that is firm enough to take theshape of its container but spreads when poured, says Brooks.

Synergizing for functionality

Brooks provides this analogy describing LBGs water-holdingcapabilities compared to other common gums: LBG is like a balloon. If youfill a balloon with water, it only holds the water as long as it is not broken.Once the balloon breaks, the water is freed and the balloon cannot be reused.Thus, once the LBG sac is broken, it never returns.

A sponge-type gum, such as guar, absorbs water. And like a sponge, guarcan fill with water, release water, reabsorb water and absorb even more water,says Brooks. This makes for a very desirable marriage: LBG and guar gum. Thetwo work together very well.

An application example is cream cheese. Cutting through cream cheese breakssome of the hydrated LBG molecules. But the guar picks up the water, preventingsyneresis.

That is what is so unique about LBG; it has extremely functionalsynergistic interactions with other gums. Besides guar, it also works well withxanthan and certain carrageenans, says Brooks. Combined with xanthan at a1-to-1 ratio, when heated, LBG will form a true, elastic gel, which is a gelthat takes the shape of its container and maintains that same shape once it isreleased from the container, much like gelatin. The heat provides the energy topromote cross-linking between the xanthan molecules and LBG.

With kappa carrageenan, LBG also creates a true gel, similar to a gelatinproduct, adds Brooks. This synergistic blend is often used in shelf-stablegel desserts such as fruit-cup gel products.

Flowerman adds, No other hydrocolloid works quite as well as LBG, with alittle going a long way.

When it comes to select frozen products, particularly ice cream, LBG is thestabilizer of choice. Since LBG is hydrophilic, it is very effective inpreventing syneresis and for controlling the formation of ice crystals in alltypes of frozen applications, says Brooks. In frozen soups, gravies or icecream, this water-binding capability will prevent or retard ice crystalformation as the finished product goes through numerous freeze-thaw cycles, fromthe time of manufacture until the consumer gets it home and freezes. There willbe additional freeze-thaw in the consumers freezer as well.

LBG also has application in meat products. Combined with all three typesof carrageenan, this stabilizer system is readily injected or tumbled onto meatand helps the meat retain moisture, says Flowerman. He notes that accordingto the Federal Register, carrageenan, LBG and xanthan gum blends incombination, are not to exceed 0.5 percent in formulations; not permitted incombination with other binders approved for use in cured pork products.

Nieto adds, Bakery fillings such as pumpkin pie, fruit pie and fruit tartfillings also benefit from the addition of LBG. When added to the recipe atabout 0.2%, the result is a filling that is bake stable and not prone to boilout. While cold-water-soluble gums thin out when heated, LBG actually developsits viscosity during the baking step, helping to bind the water and the producttogether, thereby preventing boil out.

A variety of straight LBG ingredients are available to the industry. Somegrades contain dark seed skin specks, similar to those found in vanilla bean icecream, while others have no specks at all, the only difference being aesthetics.Degree of viscosity development also varies, based on the initial quality of theseed and the way it is kibbled. Hydrated LBG powders eliminate lumping that canoccur when regular LBG is added too quickly to hot water.

Flowerman concludes by saying that, in the past two years, the LBG industryhas been troubled with dramatic price increases and uncertain supplies. However,nothing beats the functionality and naturalness of LBG, so it pays to workclosely with suppliers to identify the best synergistic combination ofingredients the biggest karat.

Donna Berry, president of Chicago-based Dairy & Food Communications,Inc., a network of professionals in business-to-business technical and tradecommunications, has been writing about product development and marketing for 11years. Prior to that, she worked for Kraft Foods in the natural-cheese division.She has a B.S. in Food Science from the University of Illinois in Urbana-Champaign. She can be reached at [email protected].