From Starch to Maltodextrin

July 2005

From Starch to Maltodextrin

By Donna BerryContributing Editor

A positive outcome of the low-carb craze is an improved understanding that not all carbohydrates are created equal. In fact, some are downright essential for enabling food manufacturers to provide varied and flavorful offerings to today's busy consumer. Only those who cook from scratch can avoid carbohydrates classified as or derived from starch, as starch and maltodextrin ingredients are the secret to the success of many convenience and processed foods.

Branches and chains Plants produce starch through the photosynthesis of sugar. Food starch is primarily derived from corn, wheat, tapioca and potato plants, but other sources, such as rice and arrowroot, find their way into various food products.

The same general chemical and physical considerations apply to all plant starches before they are processed into ingredients. They consist of large molecules composed of chains of glucose units linked together to form one of two polymers. Amylose is the mostly straight-chain polymer, with long chains of glucose units joined by alpha 1,4 linkages. Amylopectin, the branched-chain molecule, consists of shorter chains of glucose monomers linked by some alpha 1,4 linkages and many alpha 1,6 branch points. The proportion of these two polymers in any given starch granule depends on the plant of origin, which also influences the number of glucose units.

Amylose and amylopectin are inherently incompatible molecules. Amylose has a lower molecular weight with a relatively extended shape, and amylopectin is much larger, but also more compact. Amylopectin typically consists of branched chains of 20 to 30 glucose units; each molecule can contain as many as 2 million glucose units. On the other hand, amylose chains vary in length, starting with about 200 glucose units to more than 20,000.

Most native starch has about 20% to 30% amylose (tapioca can have lower amounts), and the rest is amylopectin. However, plant-breeding techniques have allowed for the development of starches with varying ratios of amylose to amylopectin. For example, the term "waxy" describes starch that is almost completely amylopectin. This takes advantage of amylopectin's unique functionality, as waxy starches form thick, clear pastes, but gel only at very high concentrations, such as 30%. On the other hand, standard cornstarch, at 25% amylose, forms a gel at a level of 4% to 5%. High-amylose starches, which contain 50% to 70% amylose, have their own set of unique properties: film formers, oxygen and fat barriers, ingredient binders, and quick-setting, stable gels.

One way that starch ingredients vary in how they thicken, gel or bind, as well as provide mouthfeel and sheen to a food system, is their ratio of amylose to amylopectin. Amylose and amylopectin chain length also influences performance.

By molecular design, long, straight-chained amylose is more soluble in water, but creates a less-viscous solution than branched-chain amylopectin. "A good rule of thumb to remember is that amylose gives a short texture and gels upon cooling," says Brenda Waite, technical service, Tate & Lyle, Decatur, IL. "Amylopectin, on the other hand, provides more viscosity and does not gel, because the molecular branching inhibits reassociation."

Shape impacts performance Amylose and amylopectin molecules are packed tightly into the solid starch granules where they strongly associate via the many possible hydrogen bonds along the glucose units. In some regions of the granule, the molecules are so regularly ordered that they form a very strong, crystalline structure. However, in other regions, the molecules are more random and have an amorphous, readily disrupted structure.

Unlike glucose, ordinary starch granules are not soluble in cold water. They form an opaque suspension, which, upon heating, slowly becomes translucent as the granules swell and the suspension transforms into a viscous solution, a process referred to as gelatinization.

Upon heating the solution, the molecules' energy disrupts the weak, amorphous regions of the starch granule. This enables hydrogen bonding between starch and water molecules, making the granules absorb water and swell. Swelling, in turn, puts stress on the more-structured crystalline regions, and eventually the entire granule loses all organized structure, becoming an amorphous network of intermingled starch and water that provides viscosity to the solution. The mixture requires sufficient starch to bring the molecules close enough together for thickening to occur.

The temperature range at which starch molecules disrupt varies by plant origin, the ingredient processing and other ingredients in the food system. Starches from roots, such as potato, typically require less heat to start the swelling process than do starches from grains, such as corn. In general, gelatinization begins at around 140?F, and by the time the mixture reaches a temperature of about 185?F, the granules have swollen to five times their original size.

As mentioned, the point at which the granules begin to gelatinize is identifiable by a change in appearance -- the initially cloudy suspension suddenly becomes more translucent. This results from the individual starch molecules no longer being packed so closely as to deflect light rays; thus, the solution appears clearer.

When the mixture cools, the movement of the molecules slackens. When the straight amylose molecules collide with each other, they lock firmly in place. They then connect into a rigid network throughout the liquid, and the starch paste settles into a gel. The branched amylopectin molecules have little tendency to lock together, and thus, do not produce a gel.

This is a generalization; chain length and the amylose-to-amylopectin ratio influences the ability to form a gel. For example, ordinary potato starch's very long amylose chains do not readily lock, making a very viscous starch paste that remains a paste when cooled. Since starch gelatinization is critical in bread making -- swollen starch granules gel between gluten strands and provide bread with structure -- ordinary potato starch is typically not used.

For amylose-containing starches that do gel, changes often take place in the gel upon cooling. The amylose molecules become less soluble and tend to aggregate and partially crystallize. This is referred to as retrogradation and is the complete opposite of gelatinization. When the gel shrinks, some of the liquid separates from the gel, which is called syneresis. Retrogradation occurs very slowly, if at all, in waxy starches because the amylose and amyloselike fractions are minute and very dispersed.

Better breeding Advanced breeding techniques have enabled Avebe Group, Veendam, the Netherlands, to produce a GMO-free waxy potato starch with more than 99% amylopectin. "Eliane(TM) combines the superior functionality potato starch is renown for with a unique twist -- a short, shiny texture," says Dale Bertrand, manager of research and commercialization, food starch division Avebe America, Princeton, NJ.

"Amylopectin potato starch exhibits the very high viscosity of regular potato starch without the salt sensitivity," continues Bertrand. "This means that now there is a commercially available, cost-effective alternative to waxy maize starch. It's cost effective because you need less to get the same result. Regular potato starch contains about 20% amylose, which can increase solution opacity due to the retrogradation that comes with amylose content. Formulators trying to avoid amylose were previously limited to waxy maize starch." He notes this new starch "provides the same stability as waxy maize starch, along with potato starch benefits such as high viscosity and a clean, neutral flavor." Ordinary potato starch provides finished products with a matte finish, he notes, while this new starch offers clarity and a smooth, glossy appearance.

This new amylopectin potato starch was developed through classic plant breeding at Averis, the seed company owned by Avebe. It has been growing this potato plant on a commercial scale for three years and has stored enough starch for a global launch at the 2005 IFT Annual Meeting + Food Expo®. The first commercial application has taken place in the Asia Pacific Rim with a ramen-type noodle. "These noodles can be cooked with simply hot water. They do not require boiling water," says Bertrand. "Another application is in emulsified meats." The starch starts binding water at a lower temperature than corn starch, he notes, which means more meat juices are retained in the product. It has a higher water-binding capacity than native potato starch in meat systems.

These new starches from Avebe not only offer the benefits of breeding technology, but are also available with various degrees of modification to meet specific application needs. "A full range of modified versions of this amylopectin potato starch are available," says Bertrand. "For example, pregelatinized Eliane is available for instant applications, while a highly crosslinked and substituted version works in retort and high-shear applications."

At the USDA Agricultural Research Service (ARS) Western Wheat Quality Laboratory, Pullman, WA, scientists are field-testing a soft, white spring wheat, Penawawa-X. This is the first commercial, soft white spring wheat with 100% amylopectin starch, which is called "full waxy." As such, it pastes at lower temperatures and swells with more water than regular or partially waxy wheat starches (those containing less than 25% amylose). Waxy starch gels also do not lose water with freezing and thawing.

Craig Morris, a cereal chemist who directs the ARS lab, developed this wheat using conventional plant-breeding techniques that enabled him to combine three deficient forms of the gene for granule-bound starch synthase (GBSS), the enzyme responsible for making amylose. Since the deficient forms can't make GBSS, no amylose is made, either. Morris sees such full-waxy starches as food-bodying agents, shelf-life extenders and shortening replacers.

Ordinary is uncommon Breeding techniques enable scientists to modify the starch polymer content of plants. However, even such native starches are often undergo processed for further improved functionality.

Native cook-up starches have numerous limitations in stability and shelf life. Such starches, though, are extremely economical. "Regular cook-up starches can be used in any type of food application that will be heat processed and consumed right away," says Tonya Armstrong, senior applications scientist, Grain Processing Corporation (GPC), Muscatine, IA.

"When a consumer wants to prepare a food item with limited or no shelf stability and use it in less than six hours, a commodity starch can be used," says Tom Luallen, technical director, Cargill Food & Pharma Specialties, Minneapolis. "However, if there is extended time in the refrigerator or freezer, specialty starches are an excellent way to achieve shelf life."

Because we live in a world of prepared, ready-to-eat convenience foods, ordinary cook-up starches popularity has fallen off. Fortunately, scientists have developed a variety of ways to modify starch to provide desired stability and shelf life.

Manufacturing starch ingredients begins by wet-milling the plant source into a slurry. "The starch slurry is then dried, with or without any physical processing. These ingredients are referred to as native starch," says Waite. Native starch is also often called regular, traditional and ordinary. "The starch slurry can also be modified by chemical and/or enzyme addition," she says. Such starches are referred to as "modified." Consequently, they also are not considered "natural" when it comes to food labeling. "It is important to note that the drying process can impact the performance characteristics of the starch as much as chemical or enzyme additions," she notes.

"Basically, starches are processed in order to enhance or repress inherent properties as appropriate for a specific application," says David Huang, senior market development manager, nutrition, new business and pet foods, National Starch Food Innovation, Bridgewater, NJ.

Five primary technologies modify starches: · Thinning, hydrolysis with an acid or enzyme, or a combination of the two, decreases the overall molecular weight of the starch and creates more reducing ends. These starches do not thicken when hot and remain easy to stir, but still set to a gel when cool.

· Dextrinization is a dry reaction using heat and acid to increase the solubility and stickiness of starch. Dextrins are often used for film-forming.

· Oxidation creates a negative charge, which is excellent for meat batters and breadings. This also increases the whiteness of the starch.

· Crosslinking and substitution "are the most common forms of starch modification," Waite says. "Crosslinking is a chemical process that creates linkages within a starch granule. This strengthens the granule allowing for more acid, shear and heat stability. Substitution involves adding chemical groups to the starch granule for increased water-holding capacity, freeze/thaw stability or lipophilic characteristics." She notes that combinations of modifications are common, particularly substitution with crosslinking.

"Crosslinking of starch can be thought of as a means to 'spot weld' the granule at random locations, reinforcing hydrogen bonding and inhibiting granule swell," says Huang.

Depending on the desired function and application, the degree of crosslinking can range from a little to a lot. "In general, as the degree of crosslinking increases, the starch becomes more tolerant to acid and less likely to break down," says Huang. "This is not to suggest that the most highly crosslinked starch will give the best viscosity in low-pH food systems. It must be remembered that crosslinking inhibits granule swell, whereas high temperature, extended heating, high hydrogen-ion concentration and high energy input all tend to disrupt hydrogen bonding and enhance granule swell."

With this in mind, product designers should select a starch sufficiently crosslinked to withstand chemical and physical abuses and still give maximum viscosity. "If it happens that a moderately crosslinked starch tends to break down when cooked at low pH, the problem can sometimes be solved with a procedural change," Huang continues. "By cooking the starch at a higher pH, allowing the paste to cool and then adding the acid to reach the desired pH, a satisfactory viscosity may be reached without changing to a more highly crosslinked starch."

Substitution prevents gelling and weeping and maintains textural appearance. Thus, substitution stabilizes the starch. "Since waxy starches have no amylose, they will not retrograde or gel under normal storage conditions. However, under low-temperature or freezing conditions, a waxy paste will become cloudy and chunky and will weep, somewhat like the paste made with regular corn starch," says Huang. "This is attributed to a lowering of kinetic movement as the temperature drops, allowing the outer branches of the waxy starch to associate through hydrogen bonding and bringing about similar, but less dramatic, conditions that occur with amylose."

To prevent this condition, anionic groups are scattered throughout the granule to block molecular association through ionic repulsion, as well as steric hindrance. "The result of this treatment is a stabilized starch that produces pastes that withstand several freeze-thaw cycles before syneresis -- weeping -- occurs," says Huang.

Freeze-thaw-stabilized starches are essential to the frozen-food industry but have applications in many other areas, as well. Cold-temperature storage of other processed foods, such as canned sauces and gravies, are commonplace and require stabilized starches to maintain quality.

Modification is not always necessary for improved starch functionality. For example, National Starch Food Innovation has a line of functional native starches that deliver processing tolerance, along with superior freeze/thaw and shelf-life stability, according to Joe Lombardi, marketing programs manager. Derived from waxy maize, applications include fruit preparations, where storage stability is required, as well as products requiring a long shelf life or low-temperature storage. "Novation Prima delays the onset of syneresis and gelling while providing end-product quality and premium texture," he says.

Modification with purpose Suppliers can selectively modify starches for specific applications and purposes. For example, one line from Cargill is based on stabilized waxy maize starch and is soluble in cold water. "Naturally occurring gums such as gum arabic are widely used in the food industry to provide emulsifying, stabilizing and encapsulating properties," says Luallen. "Cargill has developed the starch-based EmCap(TM) line as an alternative to help overcome supply and quality problems related to climate and international supply from global regions where gums are sourced." One product, an instantized, lipophilic, thinned starch, is recommended for stabilizing liquid emulsions, such as beverages and concentrates; another blends stabilized waxy maize starch and dried glucose syrup. "It is an ideal encapsulating agent, as its extremely low viscosity results in greater drying capacity while its superior properties minimize the oxidation of encapsulated oils," he says. According to the company, this starch is particularly suited for spray-drying where high loading up to 65% is possible.

A modified tapioca starch serves as the main ingredient in a gluten-free bakery-mix from Corn Products U.S., Westchester, IL. It helps create a moist, expanded crumb, while enhancing the action of leavening agents. The bakery mixes are ready-to-use blends that work in a wide variety of applications. Made from corn- and tapioca-based starches, these products are marketed as "gluten-free" because they do not contain gluten from wheat, oats, rye or barley -- of particular importance for people diagnosed with celiac disease or wheat allergies.

"Gluten provides structure and texture in bakery products. Baking without gluten causes many problems, including weak or poorly developed structures and an undesirable texture," says Eric Shinsato, technical sales support manager, Corn Products U.S. "Alternative grains associated with gluten-free baking may leave a noticeable aftertaste and may cause the mouthfeel to be gritty. Expandex(TM) modified tapioca starch was developed to promote expansion of gluten-free baked items and to offer stability in the absence of gluten and gums. It provides a clean flavor and helps mask the aftertaste associated with alternative grains. It also can improve texture and consistency of gluten-free bakery products."

Instant improvements Pregelatinization is a processing technique where the starch is manipulated so that it swells to some degree in cold water, unlike ordinary starch, which requires heating. The most-common method involves heating a starch paste to its gelatinization temperature, drying on a drum dryer and grinding the dried starch to a powder. Upon reconstitution with water, pregelatinized starch has less thickening power and tendency to gel than pastes of the parent starch. Pregelatinized starch works in applications requiring more rapid hydration or room-temperature preparation, such as instant dessert mixes and soups.

"Our partner, Emsland GmbH, manufacturers a line of GMO-free, kosher-certified, pregelatinized potato starches called Emjel," says Mel Festejo, chief operating officer, American Key Food Products, Closter, NJ. "The line is extensive, with each ingredient possessing its own set of superior functionalities."

For example, one of these ingredients binds and thickens and gives good texturing and stabilizing properties in bakery products, instant puddings and desserts. It also works as a coating agent for nuts, and as a binding and texturing agent with good expansion-regulating properties, mainly for extruded, indirectly expanded snack products. Another acts as a binding and texturing agent in frozen foods, dressings, mayonnaises and creams. It provides good stabilizing, freeze/thaw and baking properties. "As a thickening and stabilizing agent with good texturing and foam-stabilizing properties, this starch can be used in instant sauces and dressing powders," adds Festejo.

Meeting organic needs Modified starches are not only snubbed by the natural-foods industry, organic food manufacturers also will not go near them. Unfortunately, many organic native starches in the food ingredient marketplace today are either very expensive or visually unappealing due to the processing employed. However, product designers can find some ingredients that deliver good results.

"We have been able to work with a farm in Brazil that has not only been free of pesticides and all other matters of concern for more than five years, but the land surrounding this farm has not been in any direct contact with polluting material for almost the same amount of time," says Philip Benyair, vice president of technical sales, American Key Food Products. "This GMO-free, kosher-certified, USDA-certified organic tapioca starch is derived from cassava root. It not only appears and functions like ordinary tapioca starch, it is also priced comparably."

This organic tapioca-starch line comes in four varieties: native, pearls, granulated and pregelatinized. "The most important applications are breakfast cereal and dry mixes such as bakery blends, as well as nutritional bars and frozen prepared foods," says Benyair. "Frozen food product developers know that nothing beats the functionality and price point of tapioca starch. Now organic meal marketers can get what they have been waiting for."

National Starch also markets organic tapioca in its native-starch line. The company recommends one of these starches for higher temperatures and shear food processing, particularly in dairy applications. Another starch is recommended for moderate temperatures and shear food processing systems, such as pasteurized puddings, desserts, soups, sauces, ice cream and other dairy applications, as well as in fruit preparations.

Life beyond the starch granule Starch can be further processed into what some call starch derivatives. Maltodextrin and corn-syrup solids are the two most-common ingredients. Both are made from a corn starch slurry hydrolyzed with either acids or enzymes.

Hydrolysis is controlled to achieve the desired end point and is described in terms of dextrose equivalent (DE), a quantitative measure of the degree of starch-polymer hydrolysis. It measures reducing power compared to a dextrose standard of 100. The higher the DE, the greater the extent of starch hydrolysis.

"As the product is further hydrolyzed -- higher DE -- the average molecular weight decreases and the carbohydrate profile changes accordingly," says Armstrong. The DE of maltodextrins is 19 or lower; 20 or above and the hydrolyzed starch is classified as corn-syrup solids.

"The higher the degree of polymerization of the base starch -- the chain length -- the fewer mono- and disaccharides present in the maltodextrin. Furthermore, the actual dextrose and monosaccharide content varies with starch source," explains Bertrand. "For example, 10 DE potato maltodextrin has a combined mono-, di- and trisaccharide level of less than 2%, while 10 DE corn maltodextrin has a combined mono-, di- and trisaccharide level of greater than 6%."

In general, formulators add maltodextrins to foods to bulk and bind without adding sweetness. Of course, each maltodextrin ingredient has its own unique set of functionalities.

"Maltrin® M500 maltodextrin is used in both high-carbohydrate energy beverages and in high-protein sports beverages," says Armstrong. "The ingredient helps improve the dispersion of a protein in the dry mix, improves the mouthfeel of the drink and provides carbohydrate in the beverage with low sweetness." The company has developed maltodextrins that also add some sweetness and greater clarity to sports drinks; these ingredients have varying levels of viscosity in solution.

Maltodextrins also have application in processed meats. "They can provide low sweetness, improve moisture retention and control browning," says Armstrong. One 5 DE maltodextrin can help improve moisture retention in a meat product while another, a 20 DE corn syrup solid, is used to help control browning in a meat application by replacing sweeteners such as dextrose, she notes.

In salad dressings, maltodextrins help provide body and cling. "They can also help partially replace gums to reduce stringiness in salad dressing," Armstrong says. "Functionality varies by DE." For example, the company's 5 DE maltodextrin helps improve the body and cling of the salad dressing. It can also replace fat due to its mouthfeel. However, while a 10 DE maltodextrin helps improve body and cling, it has a lower viscosity, she notes. Product designers can use it at a higher level in the salad dressing to replace fat or build solids, depending on the textural properties desired.

Some companies offer blends of starch ingredients for enhanced functionality in specific applications. For example, Tate & Lyle's cold-water swelling modified food starch coagglomerated with maltodextrin "provides enhanced dispersion characteristics in hot and cold liquids," says Waite. "This starch-maltodextrin blend is designed for neutral to mildly acidic food and beverage systems processed under mild conditions."

The company recently introduced a system for salad dressings, sauces and marinades. The company describes the system as an optimized combination of thickeners, texture-enhancing ingredients and Splenda® sucralose. It enables manufacturers to reformulate sauces and dressings to achieve lower calories, reduced fat or simply a high-quality product with a cold process. It appears on ingredient statements as: food starch-modified, xanthan gum, guar gum, maltodextrin, sucralose.

The system is currently supplied as a coprocessed mix ready for blending with oil and flavoring ingredients. It provides a functional stabilization system for a creamy, smooth mouthfeel without masking the unique flavors and bold spices used in sauces and salad dressings. It can be used in a variety of sweet and savory applications and pourable and spoonable dressings and sauces, including emulsified creamy dressings and vinaigrettes, as well as cold-processed sauces and marinades.

"Keep in mind that starch ingredient selection and performance also depends upon other ingredients in the formula, targeted product attributes, processing parameters, distribution and the shelf life requirements of the formulated food product," says Armstrong. "It is always important that product developers communicate these details to their starch ingredient supplier."

Donna Berry, president of Chicago-based Dairy & Food Communications, Inc., a network of professionals in business-to-business technical and trade communications, has been writing about product development and marketing for 11 years. 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] .

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