Food Product Design: Concepts - May 2005 - Through Thick and Thin

May 1, 2005

27 Min Read
Food Product Design: Concepts - May 2005 - Through Thick and Thin

May 2005

Through Thick and Thin

By Donna Berry Contributing Editor

Subconsciously, consumers often evaluate foods and beverages using a checklist that begins with appearance and ends with mouthfeel. Somewhere in between, consumers note the product's consistency, flavor, performance and texture in an order that varies in accordance with individual tastes and priorities.

For many, mouthfeel often goes hand-in-hand with consistency, and is only noticed when objectionable. Everything about a product might be perfect, but when too thick or too thin, slimy or sticky, consumption stops.

Of late, there has been an interesting development: "For some product categories, texture has become the main driver of consumer preference and can be used by product developers to differentiate their products from the competition," says Deborah Dihel, product innovation manager, National Starch Food Innovation, Bridgewater, NJ.

Going against the flow In the lab, the consistency of foods with a fluid component, as well as beverages, often is discussed in terms of viscosity. Viscosity is best defined as the property of a liquid substance or material that causes it to resist the forces of flow, shear or agitation, and represents a measure of the effects of internal adhesion and cohesion.

Fluids referred to as "Newtonian" are not affected by shear or pumping, and are considered true liquids. Water and oils are examples of Newtonian liquids.

Some fluid-based products are referred to as "thixotropic" -- their viscosity reduces as agitation or pressure is increased at a constant temperature. Anyone who has ever had trouble getting ketchup out of a bottle knows that you can shake and shake, and it appears to be stuck. Then, once it gets going, it flows quite readily. The same ketchup will become thick again upon remaining still, but once it is shaken or stirred, it becomes thinner. Ketchup, thus, is a thixotropic material.

It is this resistance to flow that is characterized in terms of viscosity. To gain a better understanding of viscosity, one must understand laminar flow. Basically, laminar flow is about friction and resistance. If a fluid is flowing over a surface, the molecules next to the surface are adhering to it and have zero speed. The molecules that are farthest away from the surface are moving at the fastest speed. This difference in speed creates friction in the fluid, with the amount of adherence between the molecules proportional to the friction. Thus, viscosity determines the amount of friction, which in turn determines the amount of energy absorbed by the flow. Viscosity is very dependent on temperature.

Viscosity typically is designated in units of centipoise (cP). In terms of average viscosities for some everyday products, the flow of water, a Newtonian liquid, measures 1 cP at room temperature. Honey, on the other hand is about 10,000 cP, while ketchup is approximately 75,000 cP. Peanut butter is very viscous, measuring about 250,000 cP.

Getting a feel for food "Ultimately, viscosity affects how a food or beverage looks, feels and tastes," says Dihel. "From a sensory perspective, viscosity can be considered to be one of the components of the more-complex term, mouthfeel. The texture of a food or beverage in the mouth affects the entire sensory experience for a consumer, including flavor perception." Therefore, viscosity's effect on mouthfeel and texture is an important variable to control during formulation, as well as understand and optimize. "The sensory experience is also linked to how a food looks and feels in your hands or on a spoon, and viscosity contributes to these attributes," she adds.

The reality is that most consumers do not know what viscosity is, but it significantly influences product trial and continued usage. It also is an important quality-control factor, with many implications not only for consumer acceptability, but also for processing and shelf life.

An entire area of science is dedicated to this attribute of food. Rheology, which is the study of those properties of materials that determine their response to mechanical force, includes not only viscosity, but other product behaviors, such as adhesion, elasticity and plasticity, as well.

"Product developers should take note that the rheology behind the sensory experience," says Aida Prenzno, vice president of research and development, Gum Technology Corporation, Tucson, AZ, as is as important, or even more important, than viscosity. "How the product feels in the mouth, tongue against palate, or how the product pours out of a bottle, or clings to a piece of lettuce, is critical to success. While we generally use viscosity as a measurement of a viscosifier's efficacy, we also need to look at the rheology of that product."

Rheologists understand the difference between rheology and viscosity -- the first is an area of study and the latter is a property. However, for the most part, even though it is not technically accurate, food and beverage product developers often will use the terms interchangeably.

Caring about consistency Controlling the viscosity of water-based products is a fundamental hurdle in the product-development life cycle of most foods and beverages. Ingredients that provide viscosity serve many functions, including gelling, stabilizing, suspending and thickening. Selecting the most-appropriate viscosifier is not as straightforward as, say, choosing a salt ingredient.

"Many factors must be taken into consideration, including the desired flow behavior or texture, the required shelf life, the production equipment available, the nature of other ingredients, and compliance with regulatory requirements," says Ray Valli, senior scientist, CP Kelco, San Diego.

"Increasing viscosity is a means to stabilize multicomponent systems, like salad dressings, soups and beverages," Dihel adds. "Increasing the viscosity of a food can retard or prevent separation of the dispersed component, such as an oil droplet, a vegetable piece or fruit pulp. The viscosity of a liquid also affects its fluid dynamics and, therefore, affects unit operations, including pumping, filling, heating and cooling. Controlling viscosity in an application and process can reap rewards in product quality, cost effectiveness and the overall sensory experience for the consumer."

For some people, visual images help. "Think of the difference in the way that air bubbles (internal phase) move through a soda pop (external phase), as compared to the way that the air bubbles move through a thick shake," Prenzno suggests. "It is simply the force of the thickened external phase keeping the air bubbles from moving."

Picking, preening and perfecting Product designers can provide viscosity through a variety of ingredients. The two most-popular categories of viscosifiers are hydrocolloids and starches.

The category of hydrocolloid refers to a range of polysaccharides and proteins that emulsify, foam, gel, stabilize and thicken, all of which impact a product's viscosity.

It's important that product developers keep in mind that viscosity is just one factor in determining the ingredient to use. "For example, some carrageenans have a very low (relative) viscosity, but they are excellent at suspending particulates because they have very long molecular chains which trap, or entrain, particles," says Prenzno.

There are four basic sources of hydrocolloids: algal, such as agar, alginate and carrageenan; animal, such as caseinate, gelatin and whey protein; botanical, such as cellulose, guar gum, konjac, pectin and starch; and microbial, such as gellan gum, xanthan gum, etc. These ingredients' primary function is alluded to in the term "hydro"colloid," where the prefix "hydro"-means water and "colloid" means a gelatinous substance. In fact, the term "hydrocolloid" is defined by Merriam-Webster as "a substance that yields a gel with water."

Some hydrocolloids form thermoreversible gels where gelation occurs on cooling or heating. Others form nonthermoreversible gels, also called thermally irreversible gels. With these hydrocolloids, gelation may be induced by crosslinking polymer chains with divalent cations.

"There was a time when using hydrocolloids to build viscosity conjured visions of low-quality finished products," says Greg Andon, business manager, TIC Gums, Belcamp, MD. "Hydrocolloids were used to lower batch costs, meet target viscosities and drive chefs crazy.

"We've come a long way. Our collaboration with our research chef, Walter Zuromski, has helped us focus on hitting the viscosity targets, but without losing the culinary integrity of the finished product," Andon continues. "Often, that means not using one hydrocolloid, but rather a blend of gums designed to meet the specific needs of a particular food. The creative combining of thickeners and emulsifiers, and taking advantage of the unique functionality of each ingredient, has proven more useful than using too much of a single thickener."

The company creates a special blend containing deodorized guar gum that is designed to impart viscosity when added to cold water and further boost viscosity after heating. "We've found this gum system especially useful for replacing roux in kitchen or production facilities," says Andon. "In the past, the off-flavor of traditional guar gum would not allow such a time-saving product. Caragum 200 is an all-natural gum system and an excellent thickening agent, adding body to various food products, such as soups, sauces and gravies."

Individual gums and blends are now widely available to the industry. "Gum Technology offers almost every single gum available to the food and allied industries. We have available all the tools one can utilize," says Prenzno. "When necessary, we use blends that contain starches, fibers, proteins or whatever else is necessary and works synergistically with the gums to create the best possible answer to the issues facing our customers' formulations and production."

One of the more-recent additions to Gum Technology's catalog of solutions is konjac gum. "Konjac gum works synergistically with xanthan gum, carrageenans and locust bean gum," says Prenzno. "Konjac gum both thickens and gels. Gels can be formed as melting, or nonmelting -- a characteristic unique to konjac gum." This gum has a high molecular weight and is stable in acidic conditions, making it an ideal viscosity builder in soups, sauces and dressings. Because this gum system is nonionic, it is relatively unaffected by salts.

"Konjac gum picks up almost five times as much water as xanthan gum, for example, and has an extremely high viscosity," Prenzno says. "It has a smooth flowing texture, more similar to starch than most gums, but does not mask flavors the way that starch might," noting that solutions containing 1% konjac gum have a viscosity of 20,000 cPs, while 1% xanthan gum solutions measure at 1,500 cPs.

"The secret is knowing the right blend of ingredients for the right application," says Florian Ward, vice president of research and development, TIC Gums. "For example, TIC Pretested® Colloid Ultrasmooth Powder is a combination of cold-water-soluble hydrocolloids that are effective in stabilizing and suspending instant dry-mix beverages once water is added to them."

The blend includes cellulose gum, xanthan gum and nongelling carrageenan, each of which provides distinctive functional and taste characteristics. "The blend is very effective in drink mixes that contain significant amounts of protein," says Ward. "This is due to the protein-reactivity properties of cellulose and carrageenan. Cellulose contributes excellent thickening properties. And, as the shear is increased, xanthan decreases in viscosity, making it easier to stir. The beverage regains the viscosity after the shear is drawn." Additionally, he notes that xanthan gum "plays an important role in adding mouthfeel and exceptional smoothness."

Product developers will agree that, in terms of providing viscosity, xanthan gum is the hydrocolloid workhorse of the food and beverage industry. Not only does it thicken, xanthan gum also stabilizes foams, emulsions and suspensions. Xanthan gum is a high-molecular-weight polysaccharide produced by bacterial fermentation. Its numerous applications and functionalities are a result of its molecular structure.

"Xanthan gum interacts synergistically with galactomannans to provide a wide range of rheological properties," says Valli. "Galactomannans are branched hydrocolloids, in which the mannose backbone is partially substituted by single-unit galactose side chains in an irregular pattern. Those galactomannans with fewer side chains and more unsubstituted regions react more strongly with xanthan gum. For example, the interaction between xanthan gum and guar gum results in a synergistic increase in viscosity, while blends of xanthan and locust bean gum produce heat-reversible gels.

"Keltrol® xanthan gum is unique in its stability to a wide range of ingredients found in foods," Valli continues. "Its pseudoplastic (decreased viscosity with increased shear rate) rheological properties make it excellent at suspension and stabilization of colloidal systems, and prevent mouthfeel from becoming too heavy and masking flavors."

Xanthan gum is considered the food and beverage industry's thickening and stabilizing standard because of its flexibility and compatibility with many ingredients and processes. For example, xanthan gum is soluble in both hot and cold water. It is stable over a range of pH levels and temperatures. It is shear reversible, as well as resistant to enzymatic degradation. It truly is one of the most-versatile gums, and is a common ingredient in products such as sauces, dressings and marinades. However, food processors sometimes encounter difficulties when trying to dissolve xanthan in water-based systems, resulting in slower processing times.

"Gums traditionally can take time to disperse and hydrate," says Andon. "Since time equals money, everyone is pushing to decrease the hydration time for gums." Recently, food scientists at TIC Gums improved upon the agglomeration process to create a product that allows a manufacturer to add xanthan gum and xanthan blends in water without the problematic lumps.

Traditionally, xanthan was slurried with oil in order to prevent lumps. "This helped prevent lumps, but it delayed the hydration of the xanthan by forming a barrier between the gum and the water," says Andon. "This is a step-change improvement. The ingredient has tremendous value to our customers because so many food manufacturers use xanthan and are looking for easier ways to incorporate it into their process." The product also eliminates excess powder in the air during formulation. "Xanthan also is the dustiest of gums, and our process creates a less-dusty particle," he adds.

Keep in mind, not all xanthan-gum ingredients are the same. In fact, certain xanthan-gum ingredients are application specific. "Keltrol® SF (smooth flow) xanthan gum gives low- and no-fat salad dressings flow properties similar to full-fat counterparts," says Valli. "A fine-mesh version, Keltrol FSF xanthan gum, is available for use in dry mixes where a smooth-flow rheology is desired. And Keltrol 630 xanthan gum is a new product with improved hydration characteristics in the presence of salts and acids. It also shows improved stability in low-pH applications (less than 3.5)."

Gellan gum, which also is produced through bacterial fermentation, has application in salad dressings, as well as other pourable condiments. "Kelcogel® gellan gum suspends herbs, seasonings and particulates for innovative dressings and marinades using fluid gel technology. It can also be used to lower starch levels in cook-up pastes for pourable and spoonable dressings, making the paste easier to process while maintaining functionality in the finished product," says Valli. "Gentle agitation of a weak gellan gum gel after it is set results in a smooth, pourable, fluid gel."

Gellan gum's molecular structure is a linear chain based on repeating glucose, rhamnose and glucuronic-acid units. In its native, or high-acyl, form, two acyl substituents, acetate and glycerate, are present. Both substituents are located on the same glucose residue, and on average, there is one glycerate per repeat and one acetate per every two repeats. In low-acyl gellan gum, the acyl groups are removed completely. Deacylation provides gellan gum in this low-acyl form. The acyl groups have a profound influence on gel characteristics. The high-acyl form produces soft, elastic, nonbrittle gels, whereas the low-acyl form produces firm, nonelastic, brittle gels, explains Valli.

From land to sea Guar gum is a widely used, general-purpose thickener and texture modifier. Guar gum, derived from plants, disperses and swells almost completely in cold water to form a highly viscous solution. Powdered guar-gum ingredients disperse and hydrate in cold or hot water, with the rate of hydration directly proportional to the water temperature, particle size of the powder and the rate of agitation. The viscosity of a 1% guar gum solution ranges from 2,000 cPs to 5,500 cPs.

Ultra guar gum powders are relatively new ingredients to the food and beverage industry. The powdered ingredient is able to achieve about 6,000 cPs in approximately two minutes. This rapid hydration speeds-up processing times. It is ideal for instant beverages, sauces, dressings and gravy mixes. Due to its "ultra power," less is needed, as compared to other guar-gum ingredients.

Guar-gum solutions are thixotropic. Many ketchup formulations rely on guar gum for viscosity.

Locust bean gum, too, is plant derived. It exerts synergistic interactions with other polysaccharides, such as carrageenan and xanthan gum.

Locust bean gum solutions can be very viscous. For example, a 1% solution typically measures at 3,000 cPs. Viscosity increases upon heating to 180?F. After cooling, a further increase in viscosity occurs. Because locust bean gum is a neutral polysaccharide, pH has little effect on viscosity in the range of pH 3 to pH 11.

Carrageenan is extracted from red seaweed and it comes in three grades -- iota, kappa and lambda. Some carrageenans can hold water very well under the right conditions; however, in general, they are not used for building viscosity.

Carrageenan has high milk-protein reactivity. For this reason, carrageenan is the ingredient of choice for keeping cocoa particles in suspension in chocolate-milk-type beverages.

In solution, iota carrageenan forms a weak gel with elastic properties. Solutions exhibit thixotropic characteristics. Kappa-carrageenan forms strong, rigid gels, while lambda carrageenan does not gel at all. In fact, lambda carrageenan is the grade most likely to contribute to viscosity. Lambda carrageenan is partially soluble in cold water and is fully soluble in hot water.

In nature, cellulose provides structure to plants and their fruits. There are many types of cellulose ingredients, and they vary by functionality, price and application.

Carboxymethylcellulose (CMC), also sometimes simply called cellulose gum, is known for providing a wide range of viscosities. Solutions are pseudoplastic, which means viscosity changes when various physical forces are applied. For example, when shear stress is increased, viscosity decreases. This viscosity change is completely and instantly reversible, and the original viscosity is regained when the shear terminates.

Because of this pseudoplastic attribute, viscosity can only be measured for CMC solutions at a defined shear rate. Thus, viscosity for CMC is often discussed in terms of "apparent viscosity," which denotes a definite value only under specified conditions. Pseudplasticity is not to be confused with thixotrophy, where viscosity reversal is time dependant. Some cellulose ingredients, such as microcrystalline cellulose (MCC), are thixotropic in solution.

Pectin is a hydrocolloid that has traditionally been viewed as a gelling agent, mainly in fruit products. All green land plants contain pectic substances, and pectin is extracted from them. Extraction and purification of pectin is rather simple, and thus many all-natural formulators consider pectin the most-natural hydrocolloid.

Pectin is essentially a linear polysaccharide containing from a few saccharide units to more than a thousand, in a chainlike configuration. D-galacturonic acid is the principal constituent of the pectin molecule, with some units partly esterified with methyl groups. The ratio of esterified galacturonic acid groups to total galacturonic acid groups -- termed the degree of esterification (DE) -- influences the properties of pectin, particularly its solubility and gel-forming characteristics.

The highest DE that can be achieved by extraction of natural raw material is about 75%. Pectins with DE from 20% to 70% can be produced by de-esterification during manufacturing.

The DE of 50% typically is used to separate commercial pectin ingredients into high-methyl (HM) ester and low-methyl (LM) ester pectin. The two groups function differently in solution. For example, HM pectin requires a minimum amount of soluble solids and a pH of approximately 3.0 in order to form gels. LM pectins, on the other hand, require a controlled amount of calcium or other divalent cations to be present for gelation to take place.

Product designers often use HM pectin in cultured dairy products, such as yogurt, as the pectin reacts with casein, preventing aggregation of casein particles at a pH below milk's isoelectric point (pH 4.6). Thus, HM pectin provides viscosity to yogurt at the same time it prevents syneresis, and thus extends shelf life.

HM pectin also provides mouthfeel to juice beverages, enabling them to mimic 100% juices. And pectin can provide a natural mouthfeel in instant fruit-drink powders. In general, however, pectin solutions show relatively low viscosities compared to other hydrocolloids, and thus have not been used for such purposes.

In recent years, advanced technologies have enabled pectin ingredients to evolve from simply gel-formers into viscosifiers. For example, Danisco USA Inc., New Century, KS, now offers yogurt manufacturers a pectin ingredient developed specifically to provide extra creaminess and viscosity while reducing costs through formulation optimization. "The Grindsted® Pectin SY series increases the viscosity of yogurt by about 20% to 30% and reduces the risk of syneresis, thus extending the shelf life of yogurt," says Ellen Trost, pectin product manager, Danisco. "The ingredient also enables higher filling viscosity, which helps prevent splashing in the plant compared to gelatin, which generally gives a lower filling viscosity at temperatures higher than 60?F to 68?F due to its melting point. This reduces mess and prevents accidents, as well as keeps product in the vat."

Pectin, like most hydrocolloids, is a natural, soluble, dietary fiber, and thus contributes to a yogurt's fiber content. "Gums are soluble dietary fiber, so formulators can choose a gum system that performs the specific viscosity functions they need, and at the same time boost the fiber level of their finished product," Andon adds. "For example, TIC Pretested Gum Arabic FT allows formulators to add fiber without adding unwanted viscosity to the finished product. On the other hand, GuarNT Bland can be added in applications like nutritional drinks to provide body and additional viscosity while still adding fiber."

Adding body -- not calories Gum arabic is an example of a hydrocolloid that is soluble in twice its weight of cold water. It provides body but does not thicken the solution. The viscosity of gum-arabic solutions increases slowly in concentrations as high as 25%. At concentrations higher than 25%, the viscosity increases much more rapidly in proportion to gum content. Increasing temperatures moderates the viscosity.

Indeed, developing viscosity does not always mean high viscosity. "Compared to most other gums, acacia gum is best known for providing functionality and health benefits without having much of an impact on viscosity," says Sebastien Baray, technical manager, Colloides Naturels Inc., Bridgewater, NJ. "Acacia gum's viscosity curve remains flat up to 15% to 20% concentration. For instance, the viscosity of a 25% acacia gum solution is only 80 cP.

"But on the other hand, acacia gum is widely used to provide just a little bit of mouthfeel to low-juice-content beverages. It does this at levels as low as 1% to 2%," Baray continues, nothing that "the rounded texture provided by acacia gum makes the beverage taste like a pure fruit juice. It is ideal for the development of today's increasingly popular low-sugar, low-carbohydrate juice drinks."

Apart from improving the texture of lower-sugar beverages, acacia gum is more often used for its health benefits, which include being a soluble fiber. "As a soluble fiber, acacia gum functions as a prebiotic by stimulating intestinal microflora without any side effects," says Baray. "Our Fibregum(TM) range contains a guaranteed level of 90% soluble fiber on a dry-weight basis."

The fact that most gums are actually fibers and are used at low levels means that they have little caloric impact on formulations. "Most gums are treated as a carbohydrate and are calculated as possessing four calories per gram," says Prenzno. "However, feeding tests indicate that there is no real caloric value to most of the gums. The gums are primarily dietary fiber, and pass through the system largely unmodified. Also, since gums are used at very low levels, typically 0.1% to 0.5%, there is no real impact on the nutritional profile of a product. This makes gums an excellent choice for calorie- or carbohydrate-reduced products. This is especially true when compared to many traditional starch ingredients -- which often have usage levels in the range of 3% to 6% or higher -- and measure out at four calories per gram."

Starting with starch The second category of viscosifiers -- starch -- means "stiff" or "strong" in German. Starch-containing products are the original viscosity builders of water-containing foods.

Traditional starch ingredients, such as commercial flour and corn starch, might not be choice viscosifiers for industrial food and beverage manufacturing. However, the home chef is more familiar with starch ingredients than hydrocolloids, as gum and protein ingredients are not readily available for home applications. Fortunately, today's suppliers to the industrial food and beverage industries have been able to extract and refine the starch components of various plants, turning them into highly functional viscosifiers.

Plants produce starch from the sugars photosynthesized in their leaves. Chemically, starch is thousands of glucose units linked together as polymers. There are two basic starch molecules -- amylose and amylopectin. Amylose is a linear chain, while amylopectin has a branched structure. The proportions of these two types and their average size -- whether 10,000 glucose units or 50,000 -- depend on the plant from which they have been isolated. These differences influence the behaviors of the starch, such as how the starch contributes to a product's viscosity.

Sources of starch include corn, potatoes, rice and tapioca, and each source influences the starch's behavior. For example, dent-corn starch provides a moderate viscosity with a short texture, while waxy-corn starch has a much higher viscosity and is nongelling. Potato starch's large granules give the highest viscosity in a native state.

Starch ingredients are usually described and subsequently labeled as either native starch or modified starch. Native-starch ingredients are in their original form, the form in which they were extracted from plants, while modified starch ingredients have undergone physical or chemical modification. Such modifications enable suppliers to meet specific product or process requirements.

In recent years, advanced technologies have enabled starch suppliers to offer native starches that possess the functionality of traditional modified starches but can be labeled according to their base description. "Such native starches support the development of products that complement consumers' growing interest in clean labels and wholesome food ingredients," says Dihel.

Processors treat physically modified starch ingredients without introducing new chemical groupings. Examples of physical modification include drum drying, extrusion, spray drying and even heat treatment. Physically modified starches tend to have a more-natural image than chemically modified starch ingredients.

Very low levels of chemical modification can significantly change the rheological, physical and chemical properties of starch. Chemically modified starches are manufactured by treating the starch with chemicals so that some hydroxyl groups are replaced by either ester or ether groups. More specifically, for example, acid-thinned starch is a term usually used for a starch suspension treated with dilute acid at a temperature below the gelatinization point. The granular form of the starch is maintained, and the reaction is ended by neutralization, filtration and drying once the desired degree of conversion is reached. This results in a reduction in the average molecular size of the starch polymers. Acid-thinned starches tend to have a much lower hot viscosity than native starch properties and a strong tendency to gel when cooled.

Crosslinking is a term used to describe the chemical process of connecting two hydroxyl groups on neighboring starch molecules. Crosslinking makes starch granules more resistant to heat, acid and shear.

Starch ingredients also are characterized by their treatments necessary for formulation use. For example, cook-up starches need to be cooked before they develop their functional properties. Instant starches have been pregelatinized and do not need to be cooked.

One method of instantizing involves cooking a starch slurry, drying it on a drum dryer, then grinding it to the desired particle size. Such pregelatinized starches lose their granule integrity, which often reduces stability and water control compared to cook-up starches.

Another instantizing method, spray cooking, retains the granule structure. Tate & Lyle, Decatur, IL, uses traditional drum drying and spray drying, as well as a proprietary process that keeps granules intact. The company notes that these granule instant starches maintain quality attributes, such as gloss and smooth texture, and provide the stability and water-holding characteristics of a cook-up starch.

Such pregelatinized starches can provide a variety of special functionalities. For example, the larger particle size slows the hydration rate for better dispersion. The size also adds pulpiness to mimic various fruit and vegetable solids. Agglomerization of such pregelatinized starches also improves dispersibility.

Processors can agglomerate both cook-up and instant starches to improve their dispersibility in liquids, or to modify their flow properties or density. A second material, such as maltodextrin, might be present to serve as binder or inter-particle adhesive.

Native, functional, flexible starches As mentioned, suppliers are able to use proprietary technology to provide formulators with native starch ingredients that possess the functionality of traditional modified starches.

Recently, National Starch introduced a line of functional native starches that not only delivers process tolerance, but also is said to possess superior freeze/thaw and shelf life stability. "Novation® Prima 600 is particularly well suited for frozen and refrigerated food products" says Dihel, noting that the starch ingredient is recommended for low-to-moderate temperature and shear food processing at a neutral pH.

The company derives these functional native starches from waxy maize for use in various applications, such as fruit preparations, where storage stability is required. In products requiring a long shelf life or low-temperature storage, the product delays the onset of syneresis and gelling while providing end-product quality and premium texture, according to the company. This ingredient is listed simply as "starch" on product statements literature and labels.

"Also of growing interest is the use of rice-based starches to viscosify foods," adds Dihel. "Rice starches possess a healthy image and provide a clean label." For example, the company's functional native rice starch, a viscosifier with process tolerance and freeze-thaw stability, helps products maintain a wholesome image.

Indeed, rice starch, with its tiny granule size, neutral taste and soft mouthfeel, is one of the food industry's best-kept secrets. Because its particles are as small as fat globules, product designers can use rice starch granules to build viscosity in reduced-fat foods. Rice starch can also add a satiny finish to sauces and soups and is hypoallergenic enough to use in baby foods. But for decades, there's been no easy way to procure the finely textured starch from milled rice grains -- until now.

Harmeet Gurava, food technologist, USDA Agricultural Research Service (ARS), Southern Regional Research Center, New Orleans, has found a highly efficient and environmentally friendly way to separate a rice kernel's tightly bound portions of starch and protein. Historically, the processes used to separate and extract rice fractions altered some of the nutritional and functional properties. It was also very expensive. Guraya's approach relies on very high pressure, using a microfluidizer that physically splits apart the starch-protein agglomerates. A single pass through this piece of equipment yields many small, individual particles of starch and protein homogeneously dispersed in a watery matrix. Processors then separate the starch and protein components with traditional density-based processes.

Managing and modifying the viscosity of water-containing foods and beverages is a necessary step in product development. Formulators have many viscosifiers from which to choose. Making the correct choice requires knowledge of processing and distribution conditions, ingredient interactions, shelf life, and, most importantly, what will score favorably with consumers during their subconscious evaluation.

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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