If ever a group of ingredients could be considered ubiquitous in processed foods, it would be hydrocolloids. From soups to meats, beverages to sauces, casseroles to ice creams, nearly every food category's ingredient legend notes the presence of a hydrocolloid -- perhaps because no other set of ingredients contributes more to body, texture and viscosity. Yet, though their use may be widespread, there is nothing common about them.
The term "hydrocolloid" broadly refers to colloidal ingredients with an affinity for water, such as gums, starches, pectin and gelatin, but those lines are blurring as manufacturers develop new ingredients. Not only can food designers find a broad palette of ingredients to choose from, but they may find wide variations among a specific ingredient. What's more, these ingredients might react differently in different systems or in combination with other ingredients.
Gums -- the big picture
Like other hydrocolloids, gums are polysaccharide chains that contain hydroxyl groups that can bind water. Similarities, for the most part, end there. The chains may be straight or branched. They may consist of a few thousand to 10,000 monosaccharide units. Typically, the type of sugar component describes a gum, such as a galactomannan (locust bean gum and guar gum) or a glucomannan (konjac). They might have side groups, such as esters and sulfates, or a positive or a negative charge. Structural differences and varying abilities to interact with other molecules determine the gum's attributes. "Each gum is completely different," says Allen Freed, president, Gum Technology, Tucson, AZ. Not only are these gums chemically different, but manufacturers can modify gums' particle size and polymer chain length, all of which can impact functionality.
One way to characterize gums is by source. Seed gums, such as guar and locust bean gums, consist of ground seed endosperm. Locust bean gum comes from the carob seed, thus it is also referred to as "carob seed gum." Tree exudates refer to gums derived from sap, such as gum acacia. Marine gums, such as carrageenan, are extracted from seaweed. Microbial fermentation produces xanthan gum. Lastly, chemical processing results in products such as carboxymethylcellulose (CMC).
These gums affect product viscosity and structure in different ways. Xanthan, exudates and seed gums are thickening agents. "The extract gums, the seaweed gums, the alginates and carrageenans are gelling agents," says John Keller, technical manager, P.L. Thomas & Company, Morristown, NJ. "They are basically long-chain polymers made up of various monomers or sugar units. For them to work, you must cross-link them to form a gel." Salts, calcium or potassium make the polymers link with each other. "It's a cross-linking of these polymers to make them knit together and trap water to form a rigid structure," he continues.
Gums often display synergy. Some react more strongly in the presence of other ingredients. Others behave in a complementary manner, offering a solution to one piece of the development puzzle, while a neighboring ingredient adds another dimension.
It's easy to describe gums in broad terms. But to more fully understand the potential of gums, it's best to look at what each brings to the bench.
All about alginates
Alginate is the most abundant marine biopolymer. Processors derive sodium alginate, the sodium salt of alginic acid, from brown seaweed. Propylene glycol alginate is a reaction product of propylene oxide and alginic acid.
"Sodium alginate reacts very strongly with calcium products. Alginate will just thicken if mixed with water, but if calcium is added to the equation, it will form a cold-water gel. Sometimes you don't want it to form a gel right away, so you add sequestrants, like phosphates, to delay the gel," says Freed.
"Alginates can form heat-stable gels," says Scott Rangus, vice president marketing and sales, Ingredients Solutions, Inc., Searsport, ME. Because of this stability, product designers commonly use sodium alginate in fabricated foods. "A good example of an alginate gel is fabricated onion rings," he explains. Manufacturers mince onions and combine them with water, flavorings and sodium alginate. They then extrude the mixture into small rings and spray with calcium chloride. "The calcium converts sodium alginate to calcium alginate, which is the gel form of alginate," he continues. "At that point, the gel is not thermally reversible. It does not melt. Once it's formed as calcium alginate, that gel is heat-stable. That's why it works well in things like the onion-ring application. Those can be battered and breaded and deep-fried and the gel doesn't melt."
Martini drinkers might notice another alginate application. The pimentos in green olives use alginate gels. Manufacturers grind red pepper, form it into strips, add alginate, set the gels with calcium and then stuff them into olives.
The long and short of gum arabic
Gum arabic, also called gum acacia, is a tree exudate from sub-Saharan Africa. Two species are approved for food use, Acacia seyal and Acacia senegal.
Most food applications will use A. seyal, while others need A. senegal for its emulsifying capability. "There's a difference in the protein content that makes the senegal a good emulsifier," Sharrann Simmons, vice president and general manager, Colloides Naturels International (CNI), Bridgewater, NJ, explains. "People use acacia gums for typically two different groups of applications. Acacia gum has been used for years to stabilize and emulsify flavor emulsions. Another major historical use has been as a film coating around nuts or chocolate centers of candies. It forms a very nice film, which is an effective barrier against any fat or moisture migration, either in or out of the candy piece."
What is unique about acacia gum is that it does not provide any viscosity. This makes it especially suitable for beverage use. For applications that require thickening, it works well combined with xanthan.
