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Bulking agents: Bulking up while scaling downBulking agents: Bulking up while scaling down

Bulking agents used to serve two elementary functions, but now with wider focus on health, fat content and calorie control, bulking agents fill many more requirements.

Lynn A. Kuntz

June 1, 1996

27 Min Read
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In simpler times, bulking agents served two elementary functions. They acted as diluents or carriers for microingredients such as colors and flavors, where the increased volume of the mix allowed it to be measured or packed much more easily. They also found wide use as fillers - inexpensive extenders for costly ingredients such as cocoa butter or nonfat dry milk.

Now, with the increasing emphasis on health, fat content and calorie control, food product designers need bulking agents that fill many more requirements. Like those used in more traditional roles, today's bulking agents should be relatively bland and inert in a particular application. But, in addition to merely taking up space, they often need to take on some of the characteristics of the fat, sugar or other caloric ingredients they have replaced. At the same time, they must help reduce calories.

Not surprisingly, many of these ingredients no longer qualify as cheap fillers. Current technology has provided a wide variety of options from both a cost and functionality standpoint.

"If you go back to the food technology of 30 years ago, bulking agent meant filler," says Cheryl Mitchell, Ph.D., vice president and head of R&D, California Natural Products, Lathrop, CA. "The object was to sell more sugar or maltodextrin and reduce the content of the other expensive ingredients. Some in the industry and in the FDA still think of these as diluents, but we've gone beyond that. They aren't always inexpensive, and they serve a functional and nutritional role."

Mass considerations

A number of factors determine whether a bulking agent works in a particular food system. These include cost, caloric contribution, functionality or inertness, as well as any benefits, particularly health advantages, attributed to the consumption of the ingredient. Often the requirements for the finished product must be met by using a combination of ingredients - in other words, a bulking "system."


As food ingredients go, those such as fat, sugar and flour are relatively inexpensive. Depending on the market conditions, they will fall well under 40 cents per pound. In fact, this often causes sugar to provide bulk in fat-reduction applications, much to the disgust of the "nutritionally correct." Water makes an excellent bulking agent in terms of cost. Often, however, especially in low-moisture applications, adding large quantities of water is not a viable option.

Some ingredients used as bulking agents, such as whey and maltodextrins, may fall in the same general price range as fat and sugar. Depending on the product, they may not give the desired result in terms of caloric content and functionality. The cost per pound of more sophisticated bulking agents usually rises dramatically, resulting in finished product costs that may cause marketing to suffer a coronary episode.

"In developing these products, one of the first goals is to get a concept that works," says Florence Kopchik, manager, food applications, Cultor Food Science, Groton, CT. "Then you can step back and look at ways to reduce the cost. If you don't develop a product that works in the first place, you won't have to worry about its cost."

Blending more expensive functional products with low-cost fillers can drop the price back into the realm of reality. Still, to gain high-tech advantages the ingredient cost often will significantly exceed that of its high-caloric counterpart. However, there can be other factors that affect cost.

"Food companies are currently under some of the most extraordinary cost pressures that they've ever been under," says Lewis Paine, president and CEO, Opta Food Ingredients Inc., Bedford, MA. "One of our basic assumptions is that companies will not pay more for something merely with added functionality."


While it's difficult to figure out exactly what the average consumer really knows about the caloric content of food, it's obvious that concepts such as "low" and "free" in fat and sugar also assuage their eating guilt. These kinds of claims help to determine the appropriate types of bulking agents.

Fat has 9 Cal/gram, so replacing it with a nonfat ingredient results in a calorie reduction. Obviously, the fewer calories in a bulking agent, the quicker the calorie reduction; but, using a 4 Cal/gram carbohydrate or protein as a fat replacement can still significantly lower the caloric content. The higher the levels of replaceable fat, the greater the calorie reductions in the finished product. Therefore, fat replacement usually makes sense.

"If your object is to remove fat, you may also find that replacing some of the sugar with other carbohydrates such as maltodextrins and syrups may make it easier to do," advises Mitchell.

Often merely replacing fat cannot generate significant calorie reductions, especially if the product contains little fat in the first place. Replacing sugar (mono- and disaccharides) calories or other ingredients that contribute 4 Cal/gram limits the options for bulking agents. Water may be cheap, but it would be unsuitable in applications that require solids. Ingredients with less than 4 Cal that can be used as bulking agents include insoluble fiber, resistant starch, polydextrose, polyols (sugar alcohols), and oligosaccharides.

"Most people just consider fat or sugar replacement when reducing the caloric content of a product," says Jit Ang, director, technical services, Fiber Sales & Development Corp., St. Louis. "But flour, for example, is just as caloric as sugar. Replacing it with a low-calorie bulking agent can generate significant calorie reductions."


Meeting cost and caloric goals doesn't guarantee success. The vast majority of ingredients, including fat and sugar, affect the finished product in a number of ways: processing, shelf life and quality attributes. Changing these ingredients invariably changes the product. One role of bulking agents is to make those changes as insignificant or as beneficial as possible.

"A good bulking agent needs to do more than just take up space," says Robert Verdi, business manager, bulking agents, Cultor Food Science. "Product developers have to look at more than one dimension."

Bulking agents often must help the finished product mimic its standard counterpart by adding or modifying solids, viscosity, lubricity, volume, spread, sweetness, water binding, water activity, color, flavor, and so on. Ultimately it sometimes becomes difficult to know when many ingredients leave off being "bulking agents" and become "fat or sugar replacements."

"Most of the time you can't use a single ingredient as a pound-for-pound replacement for sugar or fat and expect the same product," says Meera Crain, project leader, Avebe America Inc., Princeton, NJ. "You usually need other ingredients that are compatible with it in the overall system."

Additional benefits

Some bulking agents influence the acceptance of a product. They may have potential health benefits (regardless of the current FDA labeling status) - for example, fiber, oats, soy, oligosaccharides and xylitol. Products derived from fruit or minimally processed grain appeal to those looking for natural products. Others can be derived from nonallergenic sources such as rice or potato. Sugarless products appeal to people who suffer from diabetes.

The use of a particular bulking agent may be legally limited to certain categories by the FDA. In addition, the USDA puts fairly stringent rules on how much and what kinds of "binders" and other ingredients can be added to standardized meat products.

On the other hand, some of these ingredients may exhibit properties that the consumer may consider less desirable. Remember the furor over "sawdust" in bread? Then there are the inevitable debates over "natural" versus "chemical." And one problem that rears its ugly head with the increased ingestion of nondigestible compounds is the effect on the human digestive system. In fact, depending on the level, the FDA requires some bulking agents to carry an advisory warning on the label so that the consumer is aware of any potential problems. Also, let's not forget that some of these products increase bacterial fermentation in the gut.

Air and water show

As mentioned, water often makes an ideal bulking agent, particularly from a cost standpoint. It's especially useful for adding lubricity when fat is removed. However, water does not really act alone in most systems. Something must keep it in place and give it texture or viscosity, as well as help mimic the mouthfeel of sugar or fat. Added starches and gums often provide the majority of the water-binding ability, but other ingredients also bind water, including protein, other carbohydrates and fiber. All vary in their ability to hold water under a variety of conditions, such as heat, freezing and thawing, and pH.

"Fat provides fluidity, so it's necessary to have an aqueous phase when using a dry powder as a bulking agent," observes Kopchik. "Most of the fat mimetics are really just water-control systems."

Using water as a bulking agent has certain technical drawbacks. First, it won't work in a low-moisture product. Increasing water tends to create a number of stability problems. The systems typically bind water physically, and there is often a decrease in soluble solids. This means increased water activity and the potential for microbial spoilage. The tendency for moisture migration will often increase. The associated stabilizers may result in changes in mouthfeel or in flavor delivery. The dynamics of flavor perception also change significantly from a fat based system to an aqueous system.

"The basic concept in fat replacement or reduction is function of solids-to-liquids ratio," says Russ Bianchi, industrial and technical director at LSI/Specialty Products, Oakland, CA. "It then becomes a question of what are the solids and liquids. If the liquids are water active, then you will have to balance that with preservatives or stabilizers, and that may affect the flavor."

Air also functions as a bulking agent in a certain sense - as long as it's understood that it only increases product volume, not weight. If increased volume is a legitimate goal, certain ingredients can help.

"With some of the extremely low bulk density maltodextrins, you would be able to fill out a dry mix package that would ordinarily require two or three times the amount of a regular spray dried maltodextrin," says Celeste Sullivan, applications scientist, food technical service, Grain Processing Corp., Muscatine, IA.

Ingredients with an open structure or those with loosely packed particles take up more space. Agglomeration can expand volume. Some ingredients help maintain a certain volume through formulation changes, such as an ingredient that helps open the structure or that has emulsification properties.

It starts with starch

Maltodextrins are defined by the FDA as non-sweet, nutritive saccharide polymers derived from the enzymatic or acid hydrolysis of corn starch. They consist of dry D-glucose units linked primarily by alpha-1, 4 bonds, and they have a DE (dextrose equivalent) of less than 20. The DE of maltodextrins can go as low as four or five. If the DE of the starch hydrolysates are above 20, they are considered corn syrup solids. The term dextrose equivalent is a measurement of the reducing sugars expressed as dextrose. The number refers to the percentage of reducing sugars on a dry-weight basis.

Maltodextrins also can be derived from other sources. Corn maltodextrins are relatively inexpensive. Those from other sources, including potato, rice, wheat and tapioca, typically fall into a higher price range. Any further processing increases cost, but some of these products find advantages in certain applications.

"Maltodextrins with an expanded structure not only help by increasing fill volume - especially in applications with high-intensity sweetness - they also have the added advantage of being very dispersible. They disperse practically on contact with water," says Dorothy Peterson, food technologist, Cerestar, Hammond, IN.

Maltodextrins can build solids in aqueous systems and bulk in powders. They can build viscosity, control crystallization, and adjust the freezing point of a solution. They bind water due to their high percentage of polysaccharides, but not to the same extent as starches. They contain low levels of reducing sugars and affect the level of browning. They also influence the osmolality of beverages, which helps regulate the absorption of nutrients into the body.

As carbohydrates, maltodextrins carry a full 4 Cal/gram. In addition to complex carbohydrates, they contain low levels of mono- and disaccharides. Maltodextrins are considered non-sweet, but the actual sweetness level increases with DE and becomes noticeable with 36 or 42 DE corn syrup solids.

"You can use maltodextrins in general applications, but for calorie replacement, you would target it as a fat replacer," says Sullivan. "That's primarily because of the calorie content. Low DE products may work in sugar-free applications, depending on the level. For example, a 5 DE maltodextrin contains just over 1% sugar."

Many characteristics of maltodextrins and corn syrup solids depend on the DE. With increasing DE, they have better cold-water solubility, more sweetness and browning, and a higher level of hygroscopicity. Decreasing DE increases moisture retention and viscosity.

"If you are looking for a maltodextrin to provide viscosity, you want to go with the lowest DE possible," advises Peterson. "The lower the DE, the larger the percentage of high-molecular-weight materials which promote viscosity."

Other factors such as the type of starch (amylose versus amylopectin) also affect the specific properties of maltodextrins. Because the material comes from hydrolyzed refined corn starch, maltodextrins are relatively free of other components such as fat or protein. Although bland, they may exhibit a typical flavor that some have attributed to the presence of various compounds that occur naturally in corn. Agglomeration can decrease bulk density (increase volume) for use in dry mix applications.

Maltodextrins tend to be stable under most conditions encountered in food systems, including high heat and low pH. However, they may be affected by extremes.

"In a very acidic product like a sauce or salad dressing where the pH is under 3, you may get some further hydrolysis of the maltodextrin that could conceivably shorten the product's shelf life," says Peterson. "But it's rare to find many products with a pH that low."

Although corn maltodextrins are the most widely used, other types can create slightly different effects. Potato maltodextrins are derived from potato starch. The starting material contains very little fat and protein, minimizing off-flavor development. Potato maltodextrins are considered nonallergenic and have excellent clarity. As with corn maltodextrins, many of the functional characteristics of potato maltodextrins change with increasing or decreasing DE.

"DE is a key factor in determining what type of functionality you are looking for," says Avebe's Crain. "But you have to look at the overall stabilizer system you are using because each one will give you a different effect. For example, combining different maltodextrins with other stabilizers may change the gelling characteristics or the texture."

Commercial rice maltodextrins can be derived from white or brown rice, or partially polished brown rice syrup. The starting material greatly affects the properties of the maltodextrins because it contains functionally significant levels of fat and protein. The flavor is grain-like, reminiscent of cooked rice. Rice maltodextrins produce less viscosity than corn at a similar DE.

"Often when you remove the fat, you don't get the translucency or cloud produced by the colloidal emulsion," says Mitchell. "Rice maltodextrins, especially the very low DE product, used with starches have been very useful in those applications. By the nature of the process, corn gives an extremely soluble, clear product."

Rice maltodextrins and rice syrup solids may be used for other reasons. Rice is also considered nonallergenic. Most of the commercial ingredients fall under the "natural" banner because they are less highly processed than corn.

"Rice syrup and solids, particularly 26 DE, are used in bar technology to improve the chewiness and mouthfeel of high-protein, high-fiber bars," points out Joseph Hall, technical sales manager at California Natural Products. "Where humectancy is an issue they can provide moistness associated with freshness. It also seems to give lower extrusion pressures than the comparable DE in a corn syrup."

Says California Natural Products' Mitchell: "Because rice syrups and maltodextrins are not refined to the degree that the corn versions are they tend to be a little more aggressive in water retention than the analogous corn product."

Another starch-derived product that adds bulk as well as function is resistant starch. Through a nonchemical method, hydrated starch (amylose) molecules retrograde into short double helices. These associate into tight bundles called crystalites. Because these bundles are so compact, the digestive enzymes cannot penetrate and break them down.

With the Protsky method, the resistant starch assays as insoluble fiber, although some physiological studies indicate that the digestive system may handle it like a soluble fiber. The product is actually labeled as a maltodextrin in the United States. Because a portion cannot be digested, the calorie count comes in at 2.8 Cal/gram. It adds functional advantages, especially in extruded products. It increases expansion, adds strength, resists moisture absorption, and increases crispness, according to Paine.

"The product currently on the market is at about a 35% resistance level, which is economical in applications such as baking. We are looking at commercializing a 45% to 50% resistance level. That's where the cost parameter will allow a much broader variety of practical applications," Paine says.

Which whey

Another inexpensive ingredient often used as a 4 Cal/gram bulking agent is whey, a byproduct of the cheese manufacturing process. Dried whey contains approximately 75% lactose and 12% protein. Acid whey is derived from acidified milk but has been neutralized back to a pH of about 6.5. This process can change the solubility of the minerals found naturally in the whey. Deproteinized whey, which consists mainly of lactose, is also available. The protein in whey gives it much of its functionality in terms of structure and water-binding ability.

"The origin of the whey can impact performance," says Glen Ward, senior scientist, research and applications, Land O'Lakes, Minneapolis. "The composition, mainly the minerals, will vary based on the type of cheese from which it is made."

Typically, acid whey is lowest in calcium. Cheddar whey has a much higher calcium level because the minerals haven't been solubilized by adding acid. The level from mozzarella is even higher because it undergoes less acidic conditions during the process.

Calcium is a fairly critical component in the behavior of whey proteins. "By controlling the level of calcium you can either form a good networked gel, or a very aggregated, non-waterholding gel," says Ward. "The sodium level also affects the gel formation."

Since the protein affects the whey's functionality, we need to know what affects the protein. The isoelectric point of the whey proteins is 4.2. The protein solubility decreases and it may precipitate out. Heat treatments, mineral levels and long storage times also affect the solubility. Heat denatures the protein. and opens up the structure. Opening the structure promotes interactions between molecules, increases viscosity, and increases the water-holding capacity.

Because regular and deproteinized whey contain significant levels of lactose, a reducing sugar, in addition to protein, and exposure to heat results in the Maillard reaction. Whey also can be less-than-inert in terms of flavor.

"Whey can have a whole range of flavors," explains Ward. "It depends on factors like the product age and its origin. The flavor can range from fairly bland with mild cooked dairy notes to some fairly harsh and bitter flavors. It's the small peptides that tend to break down through microbial aging or during cheese processing that is the origin of some of those flavors."

Fiber options

Fiber can provide bulk, as well as a health-oriented image. Dietary fiber consists of certain polysaccharides and lignin (a cross-linked polymer of plant alcohols). These are not digested by human intestinal enzymes, but may undergo bacterial fermentation in the large intestine.

The compounds considered dietary fiber are generally split into two groups: water soluble and water insoluble. Much debate goes on over these classifications, especially in terms of physiological function. The FDA allows zero-calorie claims for the insoluble fraction, while the soluble portion must use 4 Cal/gram. Gums, pectins, mucilages and certain hemicelluloses fall into the category of soluble fiber. Cellulose, other hemicelluloses and lignin are considered insoluble.

Fiber ingredients come from a number of sources and typically contain a mixture of soluble and insoluble fiber. Most fiber ingredients, especially insoluble forms, are derived from plants - grains like wheat, soy and oats; legumes; fruit; and even trees. Purified forms are available that can bring the level of a specific fiber component up to nearly 100%. These tend to have less color, odor or flavor than their unpurified counterparts. Purified cellulose fibers derived from a variety of sources are commonly used in bulking and calorie-reduction applications, but other types may provide different functional or physiological benefits.

"It's common to combine different sources of fiber to get the finished product characteristics you need," says Fiber Sales & Development's Ang. "One of the main reasons is mouthfeel. Excess levels of one kind of fiber may produce an unacceptable mouthfeel, or sometimes you'll get an unwanted flavor."

A dietary fiber content of at least 2.5 grams per serving, or between 10% to 19% of the Recommended Daily Intake (RDI), allows a label claim of "contains fiber" or "good source of fiber." Above this level, the FDA allows "excellent source" claims.

Several factors affect the functional properties of fiber ingredients, including composition, molecular size and arrangement; fiber length or particle size; and moisture-binding abilities. For example, long, insoluble fibers often produce a gritty mouthfeel, but also may bind more water. Hemicelluloses tend to have a higher water-holding capacity than cellulose because of their structure. Lignin resists chemical and enzymatic degradation. The specific composition appears to affect the level of mineral bioavailability and bowel function.

"There are two kinds of cellulose fibers commonly used in the food industry," says Ang. "One would be considered a bulking grade. Those would have a very fine consistency and physically resemble flour. They perform very well as bulking agents for sugar and fat, as well as for flour. The second classification would be those types that are added not so much for bulking but for their functional characteristics. They can provide bulk, but they are typically used at lower concentrations to replace some of the properties of fat."

In addition to purification, certain processes can increase the functionality of fiber ingredients. Expanding the structure of refined cellulose derived from wheat increases its water retention and suspension capabilities, among other benefits. Another fiber-based ingredient - a partially hydrolyzed guar gum - allows the addition of significant levels of soluble fiber with minimal effect on texture or viscosity. However, as with any ingredient, additional processing drives the cost up. Cellulose gums such as carboxymethylcellulose and methylcellulose also fall into this category. In reality, the combination of improved performance and economic considerations tends to move these ingredients out of the realm of mere bulking agents and into the role of functional stabilizers. Still, in terms of caloric content or the ability to bind noncaloric water, they can be useful additions rather than a volumetric bulking mainstay.

Polydextrose chops calories

Polydextrose was developed as a low-calorie sucrose replacer, and it also can be used as a partial fat replacer. It is a highly water soluble polymer derived from the random polymerization of dextrose, sorbitol and citric acid through thermal processing. The non-sweet, slightly acidic powder has 1 Cal/gram. Suppliers of this ingredient have developed many variations to fit the needs of certain product categories.

"In confections where high levels of sugar replacement are needed, having a very clean-tasting bulking agent becomes important," suggests Verdi.

The original version of polydextrose tended to impart a noticeable acidity when added because of the residual citric acid. Subsequent improvements have reduced the acidic taste and the titratable acidity. These improvements also have increased the ingredient cost.

"The pH range is not less than 2.5 in the monograph," says Kopchik. "But even more important is the level of titratable acidity."

Subsequent polydextrose versions have a titratable acidity down around 0.03 milliequivalents (meq) per gram. Some of the more recent polydextrose variations have a titratable acidity as low as 0.003 meq.

"While these processes produce significant differences from plain polydextrose," continues Kopchik, "the latest version is different in that the product is hydrogenated. When we make the original form, it has residual glucose - a maximum of 4%. When hydrogenated, the glucose changes to sorbitol and the product becomes technically sugar free. Without glucose you no longer have a Maillard reaction. It's (useful) in products like hard candy where you don't want any browning, or in Europe, where they have very stringent sugar-free claims."

Polydextrose functions well as a bulking agent for both sugar and fat, or anywhere caloric solids have been removed. It is a very stable polymer in terms of heat and pH. In addition to its low caloric content, it can act as a humectant and improve texture. It can impart viscosity to a solution at a slightly higher level than an equivalent amount of sugar. It also can help lower the freezing point. Because it is amorphous, it will not crystallize and form a crisp texture. Combining polydextrose with other ingredients, particularly polyols, often can bring the system closer functionally to the sugar it replaces.

The FDA has approved the use of polydextrose in 11 categories. Products include baked goods and mixes, chewing gum, confections and frosting, salad dressings, frozen dairy desserts, sweet toppings, gelatin, pudding and fillings, peanut and fruit spreads, hard candy and soft candy. Petitions for the inclusion of polydextrose in other products are awaiting approval.

Polydextrose has other applications worldwide, such as beverages and meats. In the Far East and certain other markets around the world, it can generate fiber claims, but not in the United States. The FDA requires a laxative effect warning on foods that contain over 15 grams of polydextrose per serving.

Sweet and low (calorie)

One category that has shifted from merely alternative sweetener to sweet "bulking agent" is a group of mono- and disaccharide sugars commonly referred to as sugar alcohols or polyols. These include isomalt, lactitol, maltitol, mannitol, sorbitol, xylitol and hydrogenated starch hydrolysates (HSH). They are formed through hydrogenation of various sugars. The FDA does not classify these as sugars (mono- and disaccharides) and has recently accepted calorie claims of less than 4 Cal/ gram, ranging from 2 to 3 Cal/gram. Their exact regulatory status varies with the product, but several must be labeled for laxative effects at certain serving levels.

Although similar in structure, polyols tend to exhibit varying characteristics that affect their use. These include sweetness levels, caloric content, solubility, hygroscopicity, cooling effect, stability and laxative effect. They are all considered noncariogenic (do not promote tooth decay), and evidence exists that xylitol is actually cariostatic (prevents cavities). They are not reducing sugars so they do not promote browning under high heat conditions. They are all more expensive than full-calorie sweeteners, usually two to five times more expensive, except xylitol which is about 10 times as expensive as sugar.

The polyols supply varying levels of sweetness and can produce slightly different mouthfeels or flavors. To produce a comparable sweetness to sucrose, additional sweeteners may be needed. The sweetness of xylitol is comparable to sugar, but the levels of the others are less: maltitol (90%), HSH (60%), isomalt (60%), mannitol (50%), and lactitol (40%). Maltitol and lactitol have what is described as a pleasant sweet flavor with no aftertaste. However, the high negative heat of solution and high solubility of sorbitol give a cooling sensation when dissolved in the mouth. A similar effect occurs with xylitol and mannitol. Isomalt exhibits the least cooling effect.

"The sugar alcohols have different characteristics. It's rare that you find that one sugar alcohol is going to be a direct replacement for sugar," says Phil Olinger, director of Xyrofin quality, Cultor Food Science, Schaumburg, IL. "There are always exceptions. Isomalt can stand alone in some candies. Lactitol can be a stand-alone bulking agent in chocolate with an intense sweetener. Maltitol can almost stand alone in chocolate. As a general rule of thumb, most dimeric sugar alcohols - lactitol, maltitol and isomalt - can approach sugar in many applications aside from the sweetness."

Many factors affect the use of the polyols. For example, isomalt is the least soluble of the polyols, while sorbitol and xylitol have high solubility. Lactitol is not hygroscopic; HSH and sorbitol have a high affinity for water absorption. Their ability to lower water activity and freezing points depends on their molecular weight. Sorbitol, lactitol and maltitol come closest to sucrose. HSH will not crystallize even at high concentrations, and it can help prevent the crystallization of other sugars and polyols.

"Anywhere that sugar, corn syrup or high-fructose corn syrup is being used, polyols have applications," says Olinger. "For hard candy, I'd probably recommend isomalt with an intense sweetener - it makes a very stable hard candy - but there are some lower-priced alternatives. For baked goods, we generally look at lactitol, maltitol or isomalt and polydextrose. You get a more sugarlike texture. Isomalt and lactitol actually make a sugar cookie that snaps.

"I don't have any scientific basis to say that they will work as fat replacers," Olinger continues. "However, when working with a reduced-fat ice cream we noticed that adding higher average molecular weight hydrogenated starch hydrolysates tended to impart a smoothness we didn't expect."

Bacteria buddies

Another group of carbohydrates, fructo-oligosaccharides (FOS), also provide bulk with fewer calories. These consist of various short-chain fructose polymers that resist human digestive enzymes, and the longer chain inulin. They provide a low level of sweetness - up to 30% that of sucrose. FOS do not appear to have a negative effect on the availability of mineral nutrients. The caloric content ranges from 1.2 Cal/ gram and up, depending on the exact composition.

"Inulin and fructooligosaccharides are both self-affirmed as GRAS," says Ron Jenkins, product manager, textural technologies, Rhône-Poulenc, Cranbury, NJ. "Inulin is a simple hot water extract of chicory, so we consider it a form of a common food. You can also find inulin in bananas, endive and onion soup."

Although inulin and oligofructose are sometimes classified as water-soluble fiber and result in some of the same physiological benefits, they do not always exhibit the same process functionality in food. FOS tend to mimic more closely the effects of sugar in terms of viscosity, texture, humectancy, freezing-point depression and water activity. Because of its longer chain length, inulin is less soluble, acts like a stabilizer, and can even be processed so that it can form a gel with fat-like characteristics.

"By itself, inulin can increase the creaminess of a product - dairy, meats and others - so it can be used for fat replacement," says Jenkins. "If you put 2% inulin in skim milk, it will give it a full-fat mouthfeel."

In addition to their functional contributions to foods, these compounds create physiological advantages, according to a number of recent studies. In fact, many Japanese functional foods contain FOS for this reason. They act as probiotics by fostering the growth of beneficial intestinal bacteria known as bifidobacteria. These help suppress the activity of putrefactive organisms and their toxic fermentation products. In addition to regulating the digestive system, they appear to have a positive effect on serum cholesterol, blood pressure, liver function and cancer.

Bulking beyond 2000

It seems inevitable that the demand for bulking agents to replace fat and sugar will increase. And product designers will demand even more from them in the future - increased functionality, fewer calories, and in general "more bang for the buck." Depending on the approval and consumer acceptance of "high bulk" fat and sugar substitutes, such as olestra and D-tagatose, the role of bulking agents may shift, but it's likely that bulking agents will still be necessary to modify the expense or physiological effects.

"People are still targeting the same qualities as in the full-calorie product," says Olinger. "Whether the goal is calorie-reduced or fat- or sugar-free, (product designers) want to know how they can get the same texture, mouthfeel and stability at the lowest cost. While there's often a cost factor involved in using these ingredients, the reduced-calorie or sugar-free market does produce a higher return."

Says Cultor Food Science's Verdi: "The consumer is looking at these products as a value proposition, and they are proving that they are willing to pay a premium for the health claims they won't find in a traditional product - as long as the product gives them the type of eating experience they expect."

Several promising technologies are on the horizon. L-sugars may be able to provide bulk as well as functionality in food systems. Japan has approved Cultor's latest version of polydextrose, and the company is investigating the steps necessary for its use in this country. Opta has obtained an exclusive license from the USDA for a proprietary technology that involves co-processing starch, hydrocolloids and small amounts of oil. The process will be used over the next several years to create and commercialize unique texturizing agents that reduce fat, improve taste and increase the nutritional value of foods.

While these and other companies are directing a concerted effort toward developing the next generation of functional bulking ingredients, somewhere in a lab, a chemist will accidentally spill his lunch on his experiment and a new ingredient will be born. Now about those regulatory hurdles...

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