Starch: Stabilizer Solutions

Food Product Design

September 2000
Cover Story

Starch: Stabilizer Solutions

By Christine Homsey
Contributing Editor

For those of us who have been out of school longer than we care to admit, a refresher on starch chemistry and technology couldnt hurt. Starches are ubiquitous; they are the primary energy reserve in plants and in fact, provide 70% to 80% of the worlds calories. Starches are utilized by the food technologist, chef, baker and home cook for their various functionalities: thickening, stabilizing, texturizing, gelling, film forming, encapsulation, moisture retention and shelf-life extension.

The word starch itself can mean many different things. Individual starch molecules are referred to as starch, and the highly ordered packets or granules in which starch is arranged in the plant are called starch as well. To some people, the word starch means starchy foods and ingredients, running the gamut from rice to flour to highly modified, cross-linked specialty starches. Here we will focus on processed ingredients such as specialty commercial starches rather than starchy whole foods such as rice and corn.

A primer on polymers
Starch is formed from the linkage of simple sugar molecules into longer strands or polymers. Imagine a strand of pearls as a starch polymer; the individual pearls are the glucose (sugar) molecules, and the knots in the string between each pearl are analogous to the glycosidic bonds that hold the starch together.

Glucose can form two types of starch polymers, amylose and amylopectin. Simply put, amylose is a straight-chained, linear starch, and amylopectin is a larger, branched molecule. The very different structures of amylose and amylopectin account for their dissimilar properties and functions in food systems. The linear nature of amylose molecules causes them to line up and associate with each other very tightly, whereas amylopectin molecules tend to be less tightly bound because the branching keeps the molecules at a greater distance from each other.

Starches high in amylose, such as those made from common corn, have a tendency to form gels when they are cooked and cooled. A gel is a liquid system that has the properties of a solid because water molecules are trapped within the starch matrix; a very large amount of water is controlled by a small amount of solid material. Starches that are composed primarily of amylopectin are sometimes referred to as waxy starches. These starches are generally non-gelling and form viscous pastes when heated.

When starch granules are placed in water but not cooked, the starch can hold about 30% of its dry weight in water. The changes in volume and moisture are reversible at this point. When starch granules are heated in water, however, their molecular order is irreversibly interrupted and gelatinization occurs. As the starch slurry continues to heat past the gelatinization point, the starch granule deforms and soluble starch molecules are leached into the solution. The starch molecules and granule remnants are able to hold large amounts of water and a viscous paste is formed; indeed, this process is referred to as pasting. When starch granules are extremely swollen they are fragile and easily broken when stirred, causing a decrease in viscosity.

As the starch paste begins to cool, though, some of the starch molecules begin to reassociate and then precipitate or form a tight gel matrix. This phenomenon, known as retrogradation, or setback, is affected by the amounts of sugar, water, fat, protein and acid in a product. The tightly associated starch molecules cause water to be squeezed from the system and syneresis, otherwise known as "weeping" or "watering out," occurs. In addition to causing separated, watery products, retrogradation also contributes to staling in baked goods such as bread. Starches are often modified physically or chemically to prevent these conditions and improve their texture and mouthfeel in the finished product.

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Cooked starch characteristics
When starches are cooked and gelatinized, they take on varying attributes and it is useful to have a basic lexicon for describing their characteristics. For instance, starch texture can be described as grainy, smooth, cohesive (gummy or slimy) or gelled.

Texture of a starch paste is a result of the particle size of the dry starch powder and its cook-up properties. Body is the flow characteristics of the cooked starch paste, gel or finished product. The body of a starch paste can be described as heavy, thin, long or short and is affected by the type of starch used as a base and any modifications made to the base. When allowed to flow from a spoon, a short-bodied paste will break a short distance from the spoon, whereas a long-bodied product will string away from the spoon and will not break easily. The appearance of a paste or gel can be dull, shiny, opaque or translucent.

Most commercial starches are produced from grains or root crops such as corn, wheat, rice, cassava (tapioca) and potatoes. Starch from different sources possess different functional and quality characteristics, and starch manufacturers select base materials for modification that already have some of the attributes they desire for the end product. Starches that have not been modified are referred to as native starches.

Corn starch made from common (dent) corn produces opaque gells with a mild cereal flavor. Corn starch provides short body and is extremely prone to retrogradation due to its amylose content. Regular corn starch contains about 28% amylose and even higher amylose varieties are available at 50% to 70% amylose. Gum candies are often made with high-amylose corn starch because of its ability to produce a strong, opaque gel.

Waxy maize starches are composed almost entirely of amylopectin and therefore have the lowest tendency toward retrogradation of all common starches. They provide moderately high viscosity and are known for their long, clear pastes, but chemical cross-linking of these starches can produce a short texture typical of pudding. Waxy maize starches have a clean flavor and are frequently used in frozen food products because they are not nearly as prone to syneresis as amylose starches.

Native waxy maize typically produces a translucent paste, while native dent corn gels are more opaque. "Amylose content makes a big difference," notes Celeste Sullivan, senior applications scientist, Grain Processing Corporation (GPC), Muscatine, IA. "The higher the amylose, the more opacity you expect to see." Substitution of dent corn starch also affects clarity. "The higher the degree of substitution, the easier the starch is to cook out, the better the surface appearance and clarity," adds Sullivan. Undercooking the starch has the opposite effect, giving the paste a duller, more opaque appearance.

Native tapioca starch produces a very viscous, cohesive and translucent paste upongelatinization, although the paste loses viscosity rather quickly if exposed to moderate shear forces. Tapioca pastes have long body, a moderate tendency to retrograde, and a very bland flavor that makes them a good choice for products with delicate flavor systems.

Like tapioca, potato starch has a bland flavor and forms a high-viscosity paste that is susceptible to shear. Potato starch granules are very large compared to other starches and once highly swollen, are extremely susceptible to breakage. Potato starch turns clear upon gelatinization, provides very long body and has a low-to-moderate rate of retrogradation. Common applications for potato starch include ready-to-eat (RTE) breakfast cereals and dry cake mixes. A pulpy texture can be imparted by potato starch and consequently, it has found widespread use in tomato-based sauces such as barbecue. Because potato starch gelatinizes and achieves full functionality at a relatively low temperature of about 160˚F, it is useful in meat and other applications with a low cook temperature.

Regular rice starches produce opaque gels similar to common corn starch and also have a mild cereal flavor. Although sometimes used in baby foods, rice starches have played second fiddle to corn starch in the United States because they are relatively pricey. Waxy varieties of rice starch high in amylopectin are also available and give clear, cohesive pastes.

Wheat starch forms a cloudy, gelled paste that has short body, a high rate of retrogradation, and a slight cereal flavor. According to Ody Maningat, Ph.D., corporate director of R&D and technical marketing for Midwest Grain Company in Atchison, KS, when wheat starches are heated at a normal rate, they have relatively low viscosity compared to corn starches. When heated at a rapid rate, however, wheat starch approaches the viscosity of corn starch. Maningat says that wheat starch works well in wheat-flour-based foods, such as bakery and pastry products, and is finding use in additional areas, such as surimi products, fish coatings, soups, breakfast cereal and confections. Like rice starch, unmodified wheat starch is more costly than corn and waxy-maize starches, but Maningat says that modified versions of wheat, rice and corn are very competitive.

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Modifications
Discussions of amylose and amylopectin in native starches may seem somewhat esoteric to the food formulator because many specialty starches used in the food industry have been modified to withstand the wide range of conditions that products undergo during processing, storage, distribution and final preparation. These conditions include exposure to wide temperature ranges, pH and shear. In addition, native starches have many characteristics that can make them difficult to work with. For example, unmodified corn starch that is sold retail produces gels that are gummy, rubbery and retrogradation-prone and has limited ability to stabilize a dish that is not going to be consumed immediately. Final viscosity of native starch pastes is extremely difficult to control on an industrial level because temperatures cannot be adjusted fast enough in a plant setting, making it likely that the starch will be over- or undercooked.

When starches are modified, their functional properties can be enhanced or changed significantly. For instance, native waxy maize starches are notoriously mercurial. If undercooked they will not provide good stability and if overcooked, a stringy texture will result. Modification of waxy maize starch shortens its texture and gives it greater tolerance to the cooking process.

Starch manufacturers use several chemical and physical methods to accomplish their modification goals. Chemical techniques include cross-linking, substitution and conversion. Reagents and methods that are approved for chemical modification of starches in the United States are set forth in 21 CFR 172.892. Physical modifications include pregelatinization and heat treatment. Each modification brings unique characteristics to the finished starch, and combinations of modification processes can be used to achieve the desired viscosity, clarity, texture and freeze/ thaw stability in a food product.

Cross-linking, which is probably the most common type of modification, results in a starch that is much more tolerant of high temperatures, acidic pHs and shear than the native base starch. Cross-linking is accomplished by treating starch with a chemical reagent and results in covalently bonded "spot welds" which strengthen the granule. Various levels of cross-linking are used to achieve starches with distinct viscosities and cook-up properties, and the more highly cross-linked the starch, the higher the temperature needed to achieve gelatinization. In fact, starches can be so heavily cross-linked that they will not gelatinize in boiling water, although this is not desirable for most food systems. Only a small amount of cross-linking is generally needed in food starches to attain the desired functionality without substantially increasing the gelatinization point. In addition, cross-linking can create a stable paste that is shorter in texture. A major advantage of these starches is that they can be used in products that may undergo long-term storage, such as canned soup and jarred baby food.

Substitution, also known as stabilization, is used primarily to prevent retrogradation of cooked starch, especially in frozen and refrigerated products. During substitution, the starch is stabilized by adding a bulky chemical blocking group on the starch backbone to prevent the original starch molecules from reassociating.

Typical chemical reagents include, succinic anhydride, acetic anhydride and propylene oxide. "Substitution makes starch easier to cook out by lowering pasting and gelatinization temperature, which improves clarity," notes Sullivan. When succinic anhydride or 1-octenylsuccinic anhydride (OSA) is used as a chemical reagent for substitution, the normally hydrophilic nature of the starch polymer is combined with a hydrophobic fraction, giving the polymer emulsifying properties. "For instance, OSA-substituted starches can encapsulate oils or emulsify fat in a canned retorted chili to prevent a fat cap from forming in the cans headspace," adds Sullivan. Substitution results in a higher viscosity starch paste, albeit one with poor resistance to shear processes.

Some of the most commonly used modified starches are produced through a combination of cross-linking and substitution. These combinations result in multi-purpose starches that are freeze/thaw stable and have excellent thickening capabilities for puddings, pie fillings, sauces, gravies and dips. Instant starches that gelatinize at room temperature can be achieved through high degrees of substitution. An application that immediately comes to mind is instant pudding.

Conversion is an older form of chemical modification. Research on acid conversion was done in the 19th century and the first commercial acid-converted starches appeared around 1900. Starches can be converted with acid, oxidants, heat or enzymes to form reduced molecular-weight polymers that exhibit low viscosity. This reduced viscosity is sometimes desirable for the processing of food products that contain high solids such as candies and coatings. The adhesive and film-forming properties of these starches are employed in pan-coated nuts and candies, and their strong gelling capabilities are used to make candies such as jellybeans and orange slices. Converted starches are much more soluble than native starch upon gelatinization and form a stiff gel when they are cooled. Acid-converted starches are sometimes termed thin-boiling because of their low hot viscosity. Altering the length of the conversion process or the method used can produce starches with varied properties. When more extensive conversion processes are employed, dextrins, corn syrup solids and corn syrups can be created as well.

Instant, or pregelatinized, starches are typically made by slurrying a starch with water and then cooking it on a drum dryer or in an extruder. The cooked starch is then ground to the desired particle size and can be used in products that do not receive a heat treatment as part of their process or preparation. Most starches produced by this method lose the integrity of their granules. A finely ground instant starch gives the finished product a smoother texture than coarse grinds, but may lump if not dispersed correctly (i.e., mixed with other particles or dispersed in oil before adding to the product). Larger grinds do not lump as easily but give a coarse, pulpy texture that would be unsuitable for some products like cream sauce. Chemically modified and unmodified starches can be pregelatinized and the finished starch will bear the pasting characteristics of the starch used in the pregelatinization process. Common applications for instant starches include dry mixes such as instant puddings and soups, extruded snacks, etc.

Cold-water-swelling starches are pregelatinized starches that retain their granular integrity and are created by heating starch in an ethanol-water solution or by a special spray-cooking process. These starches swell greatly in water at room temperature and have a smooth texture similar to a cook-up product. They are sometimes used to make molded gum candies or to add viscosity during processing to prevent particles from settling while a product is being baked.

Heat treatment can produce a starch that maintains its granular integrity and exhibits greater viscosity and stability without the use of chemical reagents. Carefully controlled processes are used that either involve heating starch beyond its gelatinization point with insufficient water for gelatinization or heating a slurry below its gelatinization point for extended periods of time. Heat-treated starches retain their cook-up properties when they are gelatinized and pasted, and since no chemicals are involved in their production, they may be considered native and labeled simply as "starch."

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Special considerations
Choosing a starch for a new product can be a rather complicated affair, as many product attributes need to be considered when developing a new food product, such as appearance, structure, texture and taste. Other ingredients that go into a formulation can also have a profound effect on how a starch will perform; some of these ingredients include sugar, water, fat, acid and enzymes. The type of process used will determine which forms can be used, such as cook-up, instant and cold-water swelling.

Starches have the ability to make a product shiny, opaque or translucent and a can also make a product appear smooth, pulpy, thick, runny or gelled. Since humans are visually oriented when it comes to food selection, the importance of choosing a starch that imparts an appropriate appearance cannot be underestimated. In some instances, we expect certain food products to be dull and in others, we expect a sheen or gloss. Some products, like tomato sauces, look more appealing when they are a bit pulpy and are not considered natural-looking if they are too smooth and glossy. Sauces served in Chinese restaurants often have a shiny appearance, which results from using corn starch as the primary thickener.

In addition to helping or hurting the visual appeal of a food, starches can provide distinct structures to foods. In some cases, the starch is used simply as a thickener or a stabilizer and the resultant product is still a liquid. On the other end of the spectrum, starches that set to firm gels can form gum candies. Structure is also closely related to how texture will be perceived by the consumer. Some textural properties imparted by starches include graininess, smoothness, cohesiveness, pulpiness, crispness and chewiness. Starches are also sometimes used in reduced-fat products to mimic the creamy or slick mouthfeel of fats and oil.

Flavor is another important consideration when selecting a starch. Some starches naturally possess cereal notes or may have off-flavors from the modification process, so a very bland starch should be selected for delicate flavor systems.

"Starches generally should be relatively bland when fully cooked. Most flavor masking occurs when starches are either underprocessed or undercooked," says Sullivan. "Acetylated starches tend to have more of a sour note to them, and are used in a product, such as salad dressing, where a sour note is inherent."

Starches can also affect how flavors are released or "come off" in a product. Developers may be surprised when trying a new starch in a product that formerly utilized their companys "all purpose" starch flavorings and spices, for instance, may seem much more intense and their usage level can be greatly reduced. Also, some starches may mask top notes, delay flavor release, or otherwise diminish flavor complexity. Therefore, a starch should be used that allows the subtle nuances of a products flavor to come through.

Other ingredients in a food system may compete with starch for water for hydration or damage the starch molecules, so adding ingredients in a particular order can help ensure a starchs full potential. For instance, fats at levels of 4% or higher in a formulation may coat the starch and prevent it from fully hydrating. Therefore, oils and solid fats should be added after the starch has been gelatinized and held for the recommended period. Sugars compete with starch for water, so once again, they should be added after the starch has been cooked. Ingredients such fresh, unblanched fruits and vegetables have live enzymes that can breakdown a gelatinized starch. Products containing enzymatic ingredients should be cooked to at least 160˚F to inactivate the enzymes before the starch is added and gelatinized. Acidic ingredients are less detrimental to the product if they are added after the starch has reached full viscosity. In cases where this is not possible, a modified starch with excellent acid tolerance is necessary.

Starches are available in many forms so that they will be suitable for almost any processing situation. In cases where a thin broth or sauce with large particles is being filled, such as a canned soup, special starches provide temporary fill-viscosity to distribute particles evenly and minimize splashing. These starches then break down under retort temperatures, or over time, so that the end product will have the desired thinness. An instant or cold-water-swelling starch may be called for in situations where no heat is applied during processing or during the final preparation, as in cold-blended products or dry mixes. Modified starches will be needed for certain products, such as a cross-linked starch for high-heat processes and a combination substituted/cross-linked starch for frozen foods.

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Recent developments
Modification of starches is limited by the CFR, and most of the modification technologies used today have been around for decades. Even so, in the last 10 years, starches have been introduced which are easier to use (e.g., new varieties of cold-water-swelling starches), have special nutritional properties (e.g., resistant starches) or offer a "clean" product label (e.g., native starches). In addition, some starch companies that have traditionally focused on corn or maize products have been turning more attention to less-common starch sources such as tapioca and potato. "We have expanded our potato-starch line in response to customers looking for a wider diversity of starch-base types. The chemistry is traditional, but the base material is different than what people have used before," says Mike Augustine, director of food ingredient application, A.E. Staley Manufacturing Co., Decatur, IL.

Sally Brain, director of marketing food and new business, AVEBE America Inc., Princeton, NJ, notes, "There is a wide range of potential application areas for potato starch that have not been fully explored in the U.S. market because of the prevalence of corn and waxy-maize starches. Customers are interested in improving the quality of their products as well as saving money, and potato starches offer this opportunity. They can be used at lower usage levels than corn or waxy-maize starches and their bland flavor profile can enhance the quality of a finished product."

National Starch and Chemical Corporation in Bridgewater, NJ, recently introduced a line of tapioca-based starches that are available in cook-up, instant and easy-to-disperse forms. According to Bob OMara, National Starch and Chemical Corporation and Chemical Corporations manager of technical service and applications, these starches are suitable for use in low-viscosity applications, such as beverages or thin condiments, in which stabilization is needed without a heavy body or thickness. These starches are very bland in flavor, remain stable under various storage conditions and do not require an optimum cook to be functional. They can also be used as a substitute for gums, which often possess a "slimy" mouthfeel. OMara says that when this starch is added to a product such as soy sauce, the thin viscosity will be preserved, but the product will cling to the walls of its container, thus illustrating the increase in body.

Another base material that may finally come into its own is wheat starch. Maningat predicts that in about five years, waxy-wheat varieties that have an amylopectin content of 100% and high swelling abilities will be commercialized. These varieties will lead to waxy-wheat starch that can compete favorably with waxy-maize, potato and tapioca starches. Currently, hard white wheat with whiter starch and whiter gluten is available, as well as a partial waxy-wheat that has lower amylose content and better swelling abilities than traditional wheat starch.

In addition to less-common base materials, convenience is being emphasized more than ever in new starch development. For instance, GPCs Pure-Gel® food starches are easier to hydrate resulting in better clarity, flavor release and surface appearance, notes Sullivan. Hydration is feasible with minimal processing, which is beneficial in products such as fruit fillings where maintaining fruit integrity is desirable. In addition, the ingredient marketplace has seen a greater number of instant starches, particularly those that provide cook-up quality and stability.

"There are a number of reasons people dont want to cook starch, such as convenience, quality, processing and capacity issues," says Augustine. "Reproducibility is also important in restaurant and institutional functions. You want to be able to make the same thing every time, and it is convenient to be able to add an agglomerated starch directly to hot water or low-solids systems without having to worry about the quality of the product."

Augustine explains that enhanced technologies have led to starches with unique structures, textures and processing features. "We have products that will set to a gel without heat, which gives you a way to create short texture without having to cook a product," he says. "Being able to add a powdered starch without other diluents and being able to stir an instant-starch in with a fork are novel approaches as well."

Starch as fiber
Resistant starch (RS) cannot be digested by the small intestine and acts much like dietary fiber in the human digestive system. Resistant starches are categorized as types I, II, III and IV. Type I is physically bound within plant material and is inaccessible to the human body. Partially milled grains, seeds and legumes contain Type I RS. Type II is native granular starch found in foods such as bananas and raw potatoes. Type III is cooked, cooled and retrograded starch, some of which is resistant. Cooked and cooled potatoes contain retrograded RS, as do flaked or extruded ready-to-eat cereals. Starch that is rendered resistant via heat or chemical modification is referred to as Type IV resistant starch.

The main advantage that resistant starch has over dietary fiber is that it can be added to baked goods and other products without causing off-flavors, limiting expansion, greatly increasing viscosity or otherwise wreaking havoc during processing. RS does not absorb much water and therefore can be used in low- and intermediate-moisture foods like cookies and crackers. Commercial forms are available that contain 60% or more RS.

According to OMara, National Starch and Chemical Corporation and Chemical Corporation and the American Institute of Baking (AIB), Manhattan, KS, worked together to produce a bread containing resistant starch which scored well on traditional bread attributes such as volume, cell structure and color. Nationals resistant starches are labeled simply as starch, corn starch or maltodextrin, depending on the version used. RSs analyze as dietary fiber according to AOAC method 991.43. If sufficient amounts are added to a food product, the packages principal display panel (PDP) can make a statement such as "good source of fiber" or "high in fiber." In the United States, a "good source of fiber" is defined as a product that contains a minimum of 2.5 grams of fiber per serving, and a "high in fiber" product contains at least 5 grams of fiber per serving. (Serving sizes are set forth by Reference Amounts Customarily Consumed, or RACC, for the particular food.) The PDP cannot simply state that the product "contains fiber" unless other fibers have been added in addition to the RS. To avoid confusing the consumer, the product developer may wish to add a small amount of some other dietary fiber in addition to RS. No health claims are currently allowed for RS in the United States as exist for other fiber sources such as oats and psyllium, but that could change if evidence for the benefits of RS accrue.

Ideal applications for resistant starch include baked goods, cereal products, nutrition bars, pastas and puffed snacks. Resistant starches are incorporated into processes much like flour and, according to OMara, are not particularly hygroscopic so developers do not have to worry about ending up with a big starch ball or "fish eyes" in their product. One does need to keep in mind that 1 gram of a resistant starch ingredient does not equal 1 gram of dietary fiber. For example, National Starch and Chemical Corporation and Chemical Corporations RSs analyze as 30% to 40% dietary fiber, so to achieve the target level of dietary fiber, two-and-a-half to over three times as much RS will need to be added to the product.

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Natural and organic alternatives
Natural and organic foods have proliferated over the last few years, and increasingly, their manufacturers have pursued alternatives to chemically modified starches for thickening and stabilizing. Despite the shortcomings of some of the alternatives to modified starches, many of the companies that use them tolerate their deficiencies in the pursuit of a clean label. The good news is that the number of stabilizing options for natural and organic manufacturers is always expanding.

One popular alternative to modified starches in the natural foods industry is rice starch, although it not as acid-stable as modified starches and some thinning of the starch paste will occur under moderate shear. A short texture is typical of common rice starches, but waxy varieties that have long texture and fatty mouthfeel are available. Applications for regular varieties of rice starches include: retorted and aseptic products, molded candies, french fry and chicken coatings, and frozen products that will not undergo more than one or two freeze/thaw cycles. Starches produced from waxy varieties of rice have much better freeze/thaw performance as they are composed of about 98% amylopectin.

Arrowroot flour is made from the ground roots of a starchy tropical tuber. Because it has a thickening power about twice that of wheat flour, arrowroot sometimes substitutes for other starches, particularly by consumers who appreciate its "natural" image. Arrowroot is bland in flavor, turns clear and glossy when cooked, and is used in puddings and sauces.

Brown-rice flour is yet another option for thickening natural and organic products. Brown-rice flour includes the bran and oil fractions and has more flavor than pure rice starch, although the flavor can be reduced by ensuring that the flour slurry receives a "good cook" during processing.

Another possibility for natural and organic products is a native starch. These starches can be listed on the ingredient label without being preceded by the word "modified." As mentioned earlier, traditional native starches, such as the corn starch typically sold in grocery stores, have little tolerance to high-shear processes, acid, and high-temperature holding. These unmodified starches may also have undesirable textural characteristics when cooked and their viscosity may be difficult to control, making them largely unsuitable for industrial applications. As a result, starches have been developed that have better process-tolerance and cook-up characteristics without chemical-modification so that they may be considered natural. One example is National Starch and Chemical Corporation and Chemical Corporations Novation®, a line of starches processed to have better resistance to acid, shear and temperature than traditional native starches. The line includes potato, waxy maize and tapioca starches. The base material used will depend on the intended application. The various products can be used in retorted, hot-filled, refrigerated and some frozen foods and they generally work well in soups, dressings, condiments, fruit fillings, pudding, yogurt, gravies, sauces and pet foods. One thing to keep in mind is that in extremely demanding frozen applications, such as thaw-and-serve pies, a native starch of any kind may not fit the bill.

The great GM debate
While the genetically modified issue has been hotly debated in the member nations of the European Union for the past several years, only recently has it heated up in the United States. This year, about 40% of the commodity corn planted in the United States was from genetically modified varieties. Some of the other crops grown for starch manufacture are not produced by advanced genetic techniques as of yet. For example, most waxy maizes are still classically bred varieties.

Politics aside, some starch suppliers are choosing to avoid or segregate GM materials from their conventional materials in an effort to accommodate all customers. Assuring that GM and non-GM crops do not get mixed together requires an enormous amount of field-to-fork paper chasing as well as verification by analytical methods.

Verifying that materials have not been contaminated by GM crops requires specialized testing. The two methods currently in use for detecting genetic modifications are enzyme-linked immunoassay (ELISA) and the polymerase chain reaction (PCR). ELISAs are used to identify proteins that are expressed as a result of the genetic modification, and PCR can be used to detect specific GM gene sequences.

ELISAs have been developed into an easy-to-use dipstick form for rapid testing of soybeans and corn, and GM crop levels of as little as 0.1% can be detected. PCR is a technology developed in 1985 that amplifies foreign DNA in the sample so that the modification can be detected and, if needed, quantified.

PCR can detect 0.1% or less GM crop in unmodified crop, but false positives can result with such sensitive tests. These tests are expensive (PCR more so than ELISA) and not without drawbacks. The main disadvantage of ELISA is that the test is specific for a particular modification; that is, every time a new biotechnology is introduced on a commercial scale, a new ELISA test needs to be developed to detect that modification. In addition to the risk of false positives, PCRs disadvantages include lack of standard techniques, variations in sensitivity and risk of test contamination. Finally, while basic crops such as corn and soybeans can be tested, along with ingredients such as flour and crude starches, ELISA and PCR generally cannot detect GM in more highly refined ingredients such as modified food starches. Thus, for specialty-starch suppliers, this usually means the base materials must be tested before they are processed into starch.

According to OMara, National Starch and Chemical Corporation and Chemical Corporation has instituted PCR checks to ensure that GM crops are not being passed off as non-GM. "Getting both qualitative and quantitative results is extremely expensive, and you have to be very careful about the quality of the method that the lab is using," he says.

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Fat mimetics
About a decade ago, research was publicized showing that on average, Americans consumed more than the recommended 30% of their daily calories as fat. In light of this announcement and the fact that waistlines had generally been expanding for the past several years, consumers became very interested in fat-free and low-fat foods. The food industry was quick to respond with lightened versions of many grocery and foodservice products.

At 9 kilocalories per gram, fats can add a hefty dose of excess calories to a persons diet, and digestible carbohydrates, at 4 kilocalories per gram, were quickly identified as a possible means for reducing fat and calories. When one considers that 1 gram of starch can easily hold 3 grams of water (making the caloric content of hydrated starch 1 kilocalorie per gram), it is easy to see why starches became of interest as fat mimetics.

The unique melting properties, flavor-release characteristics, lubricity, spreadability and mouthfeel of fats make them highly palatable to humans. Therefore, food scientists have tried to find substitutes that exhibit similar properties. Tapioca starch and maltodextrin made from hydrolyzed potato starch are some of the materials that have been used to provide a fatty sensation on the tongue. Although starch-based fat replacers do help fat-reduced foods retain moisture, they do not provide the exact texture, melting and flavor-release properties of a higher fat food.

According to Augustine, demand for starches as fat mimetics has declined. "No-fat has almost disappeared because the quality of those products suffered so dramatically when the fat was taken out. Low-fat is still hanging around, although you dont see as much of that anymore," he explains.

Although National Starch and Chemical Corporation and Chemical Corporations OMara agrees that reduced-fat has been a more popular concept lately, he does not feel that fat-free is a defunct category. "Consumers still buy fat-free salad dressings and yogurt, so the fat-free area has not been totally unsuccessful."

Utilizing supplier resources
Even though certain starches are better-suited to some applications than others, the reality is that many food manufacturers use one or two basic starches in most of their products. Companies are using supplier and ingredient consolidation to achieve greater purchasing power on a single starch because of mounting pressure to cut costs.

Despite efforts to keep the number of inventoried ingredients down, the food formulator may occasionally be faced with a unique project that requires investigation of new starches. In the instance of a product duplication, the competitors product may have a certain mouthfeel that was achieved through the use of a particular starch. Or, a company may be introducing a new product that is very different from its current offerings, such as adding desserts to a line of frozen entrées.

Sometimes it is difficult to choose a starch because of the sheer multitude. Simply referring to a chart of native starch characteristics is not always useful because many starches have had their properties altered through modification. In these instances, calling upon the expertise of a starch supplier can save time and frustration on the bench and in the plant. Prior to speaking with the suppliers applications specialist, you should think about the product attributes you ultimately need to achieve, and any information you can provide on projected processing conditions will be helpful. These specialists can offer tips on incorporating the starch and can often offer starter formulas as well.

No matter what the application, there is almost always a starch that can meet your needs. The many starch bases that are available have very different characteristics, and your suppliers specialists can help you pick the one to do the job.

Christine M. Homsey is a food scientist with the consulting firm of Food Perspectives, Plymouth, MN. She has developed products for the grocery and restaurant industries and is finishing a graduate degree at the University of Minnesota. Homsey, who always has room for dessert, is an ardent fan of carbohydrates especially when they are combined with fats.

 




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