Hydrocolloid Handbook

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.

Like many other natural gums, acacia provides a good source of soluble fiber, between 75% and 95%. "Today, with all the low-carb diets and emphasis on fiber, there's a big push to fortify foods with fiber and also to reformulate, replacing some of the carbohydrates with fiber, which of course offers no calories," says Simmons.

Acacia is a GRAS compound, but FDA limits usage levels. Depending on the application, use levels vary from 1% to 80%. "People find that even adding 1% or 2% can make a distinct label impression, for example replacing either sugars or flours in a bakery product," Simmons continues. She also notes the success of adding acacia gum to low-carb and sugar-free formulations that contain polyols: "You can substitute some of the polyol with gum acacia and reduce the laxation effect considerably and still retain the low-carb labeling. Substituting some gum arabic typically doesn't impact the sweetness at all." Gum arabic is odorless, colorless and flavorless. Because it doesn't add viscosity, it's easy to add to any given formula.

TIC Gums, Inc., Belcamp, MD, recently patented a series of emulsifying hydrocolloids that includes modified acacia gum. "By the introduction of lipophilic or hydrophobic groups to the gum substrate through chemical modification, the emulsifying properties are significantly enhanced," says Florian Ward, Ph.D., vice president, research and development. "Applications include oil-in-water emulsions, e.g., beverage and flavor emulsions, salad dressings, spray-dried oils, etc."

At the present time, acacia gum is in short supply. "Any natural ingredient is going to be up and down in the supply chain," says Simmons. "Initially, there were only two or three countries that were significant exporters of acacia. Today, CNI and other suppliers are purchasing raw gum harvested from over 15 different countries in Africa. The supply situation is much improved, but in the past two years there have been some very bad crops. We are at the mercy of weather and sometimes other things that influence this natural product. One of the benefits of that is that you can claim that it is all-natural and absolutely GMO-free because there is no cultivation. When compared to other natural ingredients, such as vanilla or cocoa, the supply and pricing of acacia gum is relatively stable."

Carrageenan: gum of the sea

Carrageenan is extracted from red seaweeds, originally those called Irish moss. The story goes that, in the 1800s, an inventive Irish soul boiled some seaweed with milk and then strained the seaweed out. When the milk cooled, it formed custard that was sweetened with sugar.

"The original carrageenan processing plants were in those areas where this Irish moss was available, and it was basically just harvested off of coastal rocks," says Rangus. "Today, most of the carrageenan-bearing seaweeds come from the Philippines and Indonesia where it's farmed, and the coastal waters off of Chile. These different areas yield different types of seaweed, and those give different types of carrageenan with varying properties in terms of the types of gels they make -- whether they are cold-soluble or not cold-soluble, whether they're just thickeners, whether they're primarily used for meat applications, dairy applications and such. As a group, carrageenans are actually pretty complex in that there are three basic fractions of carrageenan: kappa, lambda and iota. These basic fractions can then be combined into many variations with different functions."

Generally, the kappa carrageenans give firm, brittle gels. Iota carrageenans provide very elastic gels, similar to those in gelatin desserts. The lambda carrageenans tend to be nongelling, thickening types.

Lambda carrageenan is harvested from wild seaweed in Chile; kappa and iota carrageenans come from seaweeds farmed in the Philippines and Indonesia. Cuttings are tied to nylon lines staked in shallow water. "In 60 days, you have a 2- to 3-foot-high plant, and those are harvested, just like you grow corn." Rangus says. "In that respect, you have a very stable raw material. Depending on the demand for the particular type of seaweed, the farmers grow more or less of it." Supplies of some other gums can be less stable because of weather conditions.

There are three types of extraction: alcohol precipitation, potassium chloride precipitation, and the natural-grade, or semi-refined, process. Natural-grade carrageenan typically costs one-third less than traditional types. This is effective in dairy and meat applications where cold solubility and gel clarity are not important.

Carrageenan's, particularly kappa carrageenan's, most unique property is its ability to react with milk protein, making it common in dairy applications. In chocolate milk, carrageenan is used at around 0.03%. "The reason it can be used at such low levels is that it complexes with the milk protein. You need much less of it to provide the thickening and cocoa suspension," Rangus says. Carrageenan suspends the cocoa and gives additional body and viscosity. Though it looks fluid, a gel network holds the cocoa particles up.

"In the carrageenans, if looking for something to suspend, we would look for something with an extremely long chain," says Freed. "You get good suspension with low viscosity by using a high-polymeric chain. If you have a long-chain colloidal suspension, you won't necessarily only get viscosity. You will get suspension."

Other thickeners, such as guar, can build body, but not suspension. In chocolate milk, the cocoa would settle to the bottom. This carrageenan-gel matrix also prevents fat separation in infant formula and evaporated milk and controls whey separation in ice-cream mixes or shake mixes. "In something like evaporated milk, the carrageenan level to prevent separation and settling is around 100 ppm, about 0.01%," Rangus says. "There are very, very low-use levels, specifically due to this carrageenan/protein interaction."

While carrageenan is most reactive with milk protein, it does react in lesser degrees with meat and soy proteins. Rangus describes the degree of reactivity: If the kappa carrageenan-casein synergy is 10, whey protein might be 5, meat protein might be 2 or 3 and soy protein 1 or 2.

Deli meats -- mainly turkey, although it may be found in ham or chicken -- are a primary application for kappa carrageenan because of its ability to maintain product moistness. Rotisserie chickens provide a relatively new use for carrageenan. Likewise, its injection into smoked turkeys holds more moisture in the product. Susan Gurkin, applications director, texturant systems, Degussa Food Ingredients, Atlanta, notes that the meat products tend toward single hydrocolloid use.

Kappa carrageenan reacts synergistically with locust bean gum, primarily in a water system. "You get an enhancement of the gel strength -- a more elastic gel than kappa carrageenan would give just by itself -- and lower syneresis or weeping of the gel," says Rangus. To some extent, this technology is used in dairy applications, but its primary application is in water dessert-gel applications as a gelatin substitute, especially in Latin America and Asia, because carrageenan gels do not require refrigeration.

Generally, carrageenan is recognized as a natural ingredient because it is extracted from seaweed. However, it is not listed as organic. "It can be in an organic food formulation at up to 5%, and the organic food is still organic," Rangus explains. "Most gums are in that category. They are not organic per se, but the food product doesn't lose its organic status by using them." At the high end, carrageenan might be used at 1%.

The difficulty for the food developer is selecting the best carrageenan for the job. Often, a blend of carrageenans is more appropriate. "There's almost an infinite combination of different carrageenans that make up the commercial products that are out there now," Rangus continues. "They are basically different combinations of kappa, lambda and iota carrageenan, and there's even variations within the kappa family, within the iota family and within the lambda family. Then you start looking at combinations of those different variations, and it can be very complex. You can't just pull something off the shelf." Nor can you make a simple substitution. The same carrageenan in a chocolate-milk formulation will not work the same in soymilk.

Gelling with cellulose

Cellulose, the most abundant biopolymer in the world, acts as the base ingredient for a number of gums that are chemically produced and substantially available. Moreover, manufacturing generates little variation when compared to natural gums. That they can't be labeled "natural" might be a detriment to some food applications. However, synthetic gums offer more than just consistent supply, including numerous particle sizes and viscosities.

Manufacturers use CMC, an excellent, cold-soluble thickener, in a broad range of food products, such as syrups, sauces, ice cream, beverages and bakery. Viscosity increases with molecular weight. According to Keller, CMC can replace certain sugar solids in low-calorie systems due to clarity. CMC, when processed properly, is crystal-clear due to its high degree of substitution.

"That's because it doesn't contain any protein and insoluble, unmodified cellulose fibers that can contribute opacity," Ward says, noting also that its nutritional contribution is minimal. "Several years ago, soluble dietary fiber, including gums, CMC and xanthan, were all declared to yield 4 calories per gram. With the help of the Calorie Control Council, we've petitioned the FDA to reduce this value because this does not reflect a true picture of what's happening in the gut. Soluble dietary fiber, specifically CMC, is not digested by the human digestive enzymes. Theoretically, you can use it in low-carb as a thickener, but you have to declare, paradoxically, a caloric value of 4 kilocalories per gram."

Additionally, its glycemic index (GI) is very low. "They are not digested completely," Ward continues. "You can classify them as having low-GI carbohydrates, and when you are declaring low-carb you can subtract soluble dietary fiber from the total carb."

Microcrystalline cellulose (MCC), or cellulose gel, is "very fine-mesh, almost like homogenized, spray-dried cellulose that does not dissolve in water, and therefore they do not contribute any viscosity," Ward says. "Since it's not modified, you can call it 'natural.' It will contribute opacity and fiber, so you can also use them in low-carb formulations." Because its small micron size gives a smooth texture, product designers frequently use it in whipped toppings and fat-free dressings.

Methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) are modifications of cellulose. "They've improved the functionality of the cellulose by introducing lipophilic groups, like ethers and esters," Ward says. These products gel upon heating, prevent boil-out in baked fillings and regulate viscosity during processing.

Guar's rising star

According to Paul Flowerman, president, P.L. Thomas, guar gum is the most cost-effective natural thickener. Most of the 20,000-metric-ton U.S. market comes from India and Pakistan. Although the crop is irrigated for part of the year, it is rain-sensitive. In 2004, substantial late rains in all growing areas significantly lowered prices. Still, prices have remained high for the last couple of years. "The trend is very positive," he says. "We look to a reasonably normal year for guar supplies."

Manufacturers define different grades and qualities of guar gum by the particle size, the viscosity that is generated with a given concentration, and the rate at which that viscosity develops. "Some guar gums, for example, coarse-mesh guar gums, will typically -- but not always -- develop viscosity more slowly. They may achieve a reasonably high viscosity, but will take longer to achieve. On the other hand, they will disperse better than fine-mesh, all conditions being equal," Flowerman says. A finer mesh, like a 200 mesh, requires more effort to get it into solution. "Rather than having it clump up and form what are called 'fish eyes,'" he says, " you usually need to either mix it with other ingredients or to sprinkle it into the vortex of the gum system to be agitated into solution." The correlation between mesh size and the speed of viscosity development is not necessarily unique to guar, but many other gums, such as xanthan and CMC, will develop viscosity much faster whether they are fine-mesh or coarse-mesh.

Guar can also be characterized by   taste, which, undeterred, can be considered negative -- sometimes described as "mealy." Reduced-flavor guar is one instance of manufacturers' drive to take guar to a more application-specific level. For example, P.L. Thomas offers a very rapidly hydrating guar for suggested use in instant beverages, an apt use since guar will naturally hydrate in cold water. "It can generate a thickening, then the stabilizing, activity at normal dosages well beyond what a normal guar powder can do," Flowerman says. USDA-certified organic guar gum powder is also available. He explains that the rules of the National Organic Program (NOP) are that for a food to be labeled organic, it must use an organic ingredient, if available. Companies seeking "organic" labeling can only use a nonorganic ingredient when an organic ingredient is not available.

Guar works in a very broad range of applications and is only limited by its sensitivity to performance at acidic pHs. "At pHs below 5, its effectiveness will rapidly diminish, and that's when people turn to xanthan," Flowerman says. Guar gum is often used with xanthan for its synergistic effect. Primary applications for guar include ice cream, processed foods, sauces, moist pet foods, tortillas and breads.

Konjac, locust and xanthan

Konjac is a tuber gum, sourced out of Southeast Asia, primarily China. "When exposed to a pH of 9.5 or 10, konjac loses its alkyl groups and becomes a nonthermal reversible gel," Freed explains.

Flowerman points out: "You can get more thickening out of it in a given concentration, say 1%, than any other gum that we know of. On the other hand, it certainly is not as cost-effective for certain applications. There are issues of solubility. You have to heat the solution, which makes it less versatile than guar or xanthan, but it's definitely a gum worth looking at."

It shows a very good synergy with carrageenan and xanthan. "It's a somewhat less-explored gum," Flowerman continues. "I'd say in the last 5 to 10 years it has become much better known."

Locust bean gum comes almost exclusively from the Mediterranean where processors derive it from the kernel of the carob tree. "Locust bean gum is the most costly of all the galactomannans," Flowerman explains. Guar, tara and fenugreek are also galactomannans.

"It's about six times more costly than guar, because guar can be grown in about 120 days," Ward says. "It comes from a tree that takes about 7 to 10 years to mature."

Typically, locust bean gum doesn't give cost-effective thickening alone. It's not cold-water-soluble and requires heating to 180?F, although this can be an advantage in some processing systems. Locust bean gum exhibits some remarkable synergies with other gums, such as carrageenan and xanthan. "When you mix locust bean gum with xanthan gum," Ward says, "you form a beautiful, flexible gel. It forms a heat-reversible gel. If you mix locust bean gum and carrageenan, you will form a gel that is sliceable with very low weeping, or syneresis." This is why it is frequently used in cheese products. Additionally, locust bean gum is especially good for freeze/thaw applications. It does not impart the negative taste that people associate with guar gum.

Xanthan, a biogum, is produced as a secondary metabolite during bacterial fermentation by Xanthomona campestris. "Xanthan has become the workhorse," says Gurkin. "It's fairly inexpensive and easy to use."

It is the only bacterially produced gum manufactured industrially on a large scale. "Xanthan gum has great structural integrity, and therefore it can be used under almost all processing conditions," says Flowerman. "It is characterized by rapid hydration and viscosity development. It demonstrates great synergy with other gums. Sometimes it can be used in very low concentrations to positively affect a stabilizer system or a food ingredient system. It is simply an outstanding gum."

To its advantage, it is cold-water soluble and effective over a wide pH range. It can be dissolved in very acidic solutions or those with a high pH. James Carr, Ph.D., president, Excelon Specialty Products, Lake Bluff, IL, notes that xanthan's excellent physical stability and highly pseudoplastic (shear-thinning) behavior make it an extremely versatile hydrocolloid: "Xanthan solutions exhibit a perceptible yield-value that must be exceeded in order to induce flow. These solutions tend to thin under shear conditions and then re-thicken when shear is removed, after pumping or pouring, for example. For food systems that require stabilization over a short time frame, such as instant beverage mixes, pseudoplastic thickening agents are good candidates. But to stabilize products over a longer time frame, a three-dimensional network normally needs to be formed using a weak gelling system or some other form of physical entrapment to suspend the particles."

Thermally stable, xanthan will not thin when heated to the extent that most gums will. This makes it an ideal choice for hot-filling or emulsion stabilization in a retort product.

"Xanthan is more costly than guar gum," Flowerman says, "so cost-effectiveness does become more of an issue when you're dealing with products at neutral or slightly acidic pH. Then again, it substantially replaced gum tragacanth when that gum, whose main source is Iran, fell under the trade embargo."

Studying starches

Surpassed only by cellulose in its abundance, starch is found in all green-leaved plants. Like gums, starches are carbohydrates, specifically amylose and amylopectin. "In starch, you've got two different kinds of glucose chains," explains Rhonda Witwer, business development manager of nutrition, National Starch & Chemical Company, Bridgewater, NJ. "Amylose is the linear chain, and amylopectin is very highly branched." All starches consist of one or both of these molecules, though the amounts of each vary depending on the source of the starch.

Selective-breeding hybridization creates corn that yields different percentages of amylose and amylopectin. High-amylose starches have unique gelling and film-forming properties. Because of amylopectin's branched nature, starches containing high amounts have increased viscosity stability.

Though native starches, such as corn, potato or tapioca, can impart viscosity and body, they offer a fairly narrow range of functionality. For one, they usually cannot be used at more than 6% solids because they impart high viscosity.

Manufacturers customize modified food starches to enhance certain attributes, such as thickening, increased stability, mouthfeel improvement, gelling, dispersability and clouding. Conversion by acid hydrolysis, oxidation and enzymes creates modified starches with distinct functionality depending on the method used. As a whole, viscosity is greatly reduced, allowing higher usage levels. Water solubility, gel strength and starch stability are subject to enhancement by conversion.

Cross-linking adds to the starch polymers small amounts of compounds that react with more than one hydroxyl group. Essentially, this reinforces hydrogen bonding and inhibits swelling of the granule. This provides short texture, and more resistance to temperature, acid and shear.

Stabilization imparts textural and freeze/thaw stability, as well as increased shelf life, by blocking retrogradation (reassociation through hydrogen bonding of the linear fractions). This prevents gelling and weeping. Pregelatinization, a physical modification, imparts swift viscosity development, cold-water swelling and process tolerance.

A vast variety of starches are available, so selection begins with a few basic questions. Is the product cook-up or instant? What are the processing conditions: time, temperature and shear? What other ingredients are present in the system: sugar, acid, fat, and/or protein? Are other hydrocolloids present? This last question is important, because just as synergies exist between gums, enhanced functionality exists between starches and gums.

Traditional lines are starting to blur. It's long been accepted that starches are digested. Indeed, most conventional starches, once cooked, become rapidly digestible.

Not so with resistant starches. Though technically not hydrocolloids due to their low interaction with water, resistant starches are relatively new offerings.

"Resistant starches behave as fiber in the large intestine," says Witwer. Some health benefits of resistant starches include low impact on blood sugar, increased insulin sensitivity, and positive impact on lipid metabolism and colon health. "You can develop great-tasting foods that significantly lower the blood-sugar response, which is one of the primary mechanisms of the low-carb diet. We go through a very natural and patented processing technique that encourages those linear chains of glucose to line up and crystallize, which makes it resistant to digestion," she continues. Resistant starches deliver insoluble fiber so, in most cases, they're used as a flour substitute.

Healthy hydrocolloids

"Gums have become extremely valuable in developing low-carbohydrate foods," Freed says. "When you remove carbohydrates -- the starches and the sugars -- you pick up water. You can't use starch because starch is a carb."

The answer, Gurkin says, is to use a gum: "If you're pulling some of the carbs out, a lot of times you can replace a lot of carbs with just a little bit of hydrocolloid. Such a small amount gives you so much texture and structure. The same with fat. If you're reducing your fat levels, you can replace some of that mouthfeel and texture. Hydrocolloids are very good at that."

Gurkin finds hydrocolloids also have their place in removing trans fats: "The first step in the low-trans or zero-trans switchover is switching 1:1, say a palm oil alternative. Now we're getting people that are looking at that next step. Kind of like the reduced-fat, low-fat, no-fat craze of the early '80s, the trend now is for a better balance, both flavor- and texture-wise. Again, a lot of the hydrocolloids were the ones giving the texture and the structure."

In the functional-food arena, specific gums are becoming known for certain health benefits. Some companies are promoting the bifidobacteria-protective quality of gum arabic. According to Flowerman, monographs on guar show blood-glucose reduction and stabilization. Fenugreek, a more exotic galactomannan, is becoming recognized for blood-glucose stabilization and cholesterol reduction. "Outside of the United States, it is being incorporated into a number of food products, cakes and breads, specifically for people who would like to have low-glycemic-index foods," he says.

Perhaps one of the most well-known, healthful hydrocolloids is psyllium, the functional ingredient in Metamucil(TM). A significant soluble fiber recognized for its laxative effect, it is associated with reduction of cholesterol. Product designers have formulated psyllium into cereals and baked goods. According to Flowerman, psyllium presents challenges in formulating foods, because it forms a mucilage. However, he believes it deserves a second look -- its use as a laxative and   soluble fiber is growing.

Another lesser-known hydrocolloid, guggul gum, a tree exudate from India, has also been shown to reduce cholesterol, although it does not have an FDA-recognized health claim. "The health-promoting properties of these gums as soluble fibers is receiving increased recognition beyond the gums' traditional functionality as stabilizers," Flowerman says.

When it comes to starches, "the new things we are looking at are in the area of health and wellness," says Mark Hanover, director of research, Tate & Lyle, Decatur, IL. "That includes things like resistant starches and products that can aid in the development and production of healthier, but indulgent-tasting, food products."

The proof is in the pudding

Individual gums have their own imprints, but no one size fits all. Not only does each gum behave in an individual manner, but because of synergies with other gums and ingredients, it may behave entirely different than if left on its own.

"Just as you blend spices to get a particular flavor, you blend gums to get a particular function," Freed says. "If you heat a xanthan and you heat a locust bean gum separately, neither forms a gel, but heat them up together it will form a gel. If you heat konjac alone, it won't form a gel. If you heat it in the presence of a xanthan or a carrageenan, it will form a gel. Konjac greatly synergizes xanthan. You'll use far less xanthan if you throw a little bit of konjac in there. By blending gums, you create unique functionality for different applications."

Carr explains that besides these hydrocolloid/hydrocolloid interactions, several other interactions occur between hydrocolloids and other components in foods. The effect created by kappa carrageenan and milk casein is a classic example of a desirable hydrocolloid/protein interaction. "At a given pH, food gums can interact in a controlled manner with proteins naturally present or added to food systems," he says. "But, since many gums can possess a net charge, the formulator should examine the isoelectric points of proteins present in the system to predict possible interactions at a given product pH."

Because hydrocolloid/ion interactions are also important, knowing the ionic makeup of a formulation and its ingredients can help in obtaining consistent results with gums. "In addition, many commercial hydrocolloids are tailored to specific applications and formulated with certain salts that can improve dispersion and solubility, correct for water hardness, improve clarity or modify final product rheology," says Carr.

Perhaps the best examples of hydrocolloid-lipid interactions are in the stabilization of salad dressings or beverage emulsions. In these systems, hydrocolloids can physically interact with oil-droplet surfaces and prevent flocculation and/or coalescence.

The way manufacturers incorporate a hydrocolloid into a food system will influence its behavior. "We have a line of bakery systems that are based on hydrocolloids and emulsifiers," says Gurkin. "If you were to simply take and dry-blend the hydrocolloid and dry-blend the emulsifier into the baked good, you would get a very nice product. We process them together in a specific way and we get even a greater effect. They both have their functions, and they work very well, but when we process them together, we're actually getting an enhanced effect. The reason we're theorizing this is happening is they are reacting at the right time in the baking cycle."

Product designers shouldn't overlook starch/gum combinations. Modified food starches effectively provide body to food applications -- but, at higher usage levels, can often bind flavors. "Gums can oftentimes be used to reinforce the starches' textural properties and improve overall flavor release," Carr says.

Freed notes that there is a great tradition of people relying on starches and roux as thickeners. However, other options exist. "They are starting to learn that the gums will thicken more efficiently," he says. "Because you use such a low-use level, you really don't impact the flavor. You're able to use far less flavor when you use a gum, and you get a more-natural flavor profile."

Moreover, hydrocolloid systems are cost-effective. "The cost of a blend is usually less expensive than buying the individual ingredients," Carr continues. "Even with the cost of blending involved, custom stabilizers are not that expensive." Freed also sees new development in the microbial fermentation and cellulose gums: "For the most part, the selection we have now is so great that the search for new gums tends to be for more esoteric purposes rather than general application."

It's human nature to reach for the tried and true. "I think there's a lot of potential in some of the other hydrocolloids that some people may be missing, just because they have the tendency to immediately go to the workhorse, xanthan." Gurkin says. "The hydrocolloids are very application-specific. Talk to your supplier because we're the ones that work with them in the system and understand the differences and know the questions to ask for the application."

Keller agrees: "A food developer is good at putting ingredients into products and fitting them into the finished form. They don't have the time and luxury to understand the characteristics, the usage and the handling of the individual ingredients. Use of hydrocolloids can be tricky because they require special application techniques and a special understanding of how to put them in solution. Customarily, you have to work with customers and clients in educating how to use them, and give them the most-efficient and thorough use of these ingredients."

However, Flowerman reminds us that "the food technologist serves many masters, from the applications people who want the most-palatable and effective product, to the corporation, which is concerned with profitability and price. The devil is in the details." That's something all developers know well.

Cindy Hazen, a 20-year veteran of the food industry, is a freelance writer based in Memphis, TN. She can be reached at [email protected].