Sifting Through the Ingredient Options

  Starches. Throughout the food industry, various starches have become the stabilizers of choice because they are economical and exhibit a wide range of functional properties. Suppliers offer a wide range of starches -- not just corn and tapioca, but also rice, wheat and potato -- to provide the desired effect.

  The first consideration is the temperature range at which the mix will be made up. Instant pudding or salad dressing mixes will be mixed, stored and used at cool temperatures so they require an instant starch. Most sauces or soups have a cooking step and, thus, use cook-up starches. Other products need starches that hydrate at hot, but not boiling, temperatures.

  Starches provide viscosity through gelatinization. As heat is applied, the starch molecule absorbs water and swells. The temperature at which gelatinization occurs varies. High-amylose corn starch, for example, needs a relatively long period of exposure to high heat. On the other hand, potato starch can gelatinize at temperatures below boiling.

  "The most obvious difference between potato starches and other starches is the size, shape and morphology of the granule," says Charles Brine, technical manager, food, Avebe America Inc., Princeton, NJ. "Potato starches can take up more water, more readily."

  "In some applications this means you may use 10% to 15% less potato starch than corn starch to get the same viscosity," adds Mira Crain, senior food technologist at Avebe.

  Often mixes are designed to be rehydrated at room temperature or lower. These applications require pregelatinized starch, which has been heated to the gelatinization temperature, then redried. The particle size of the granule affects the rate of rehydration.

  Some instant starches can be added directly to hot water, but that depends on the gelatinization temperature of the starch. In some cases, elevated temperatures can destroy the granular integrity and break down the starch. These may be either pregelatinized starches or starches with reduced gelatinization temperatures.

  "Reduced pasting temperatures can give the advantage of not having to go to 190 degrees Fahrenheit and holding the product at that temperature for a long period of time. Plus they give you process flexibility," says Celeste Sullivan, applications scientist, food technical service, Grain Processing Corp., Muscatine, IA. "You can put the product in hot tap water."

  While the hydration temperature of the mix determines the types of starches that are appropriate for a given formulation, the characteristics and intended use of the finished product narrow the field. In addition to attributes dictated by the native starch, the properties can be changed through chemical modification, including acid modification, cross-linking and substitution.

  "With the exception of some products destined for the retail market you don't see much unmodified starch used," says Sullivan. "Products, especially for foodservice, require more long-term stability. The customer may put them on the steam-table, or make them up, chill them, then reheat them at a later date. Common corn starches won't withstand those conditions."

  Moisture levels of traditional cook-up starches range from around 10% to 12%. Moisture in a pregelatinized or instant granular starch is about 6% or less. Redried types with very low moistures are designed to control moisture in the package by absorbing some of the moisture from the other ingredients. It's important to make certain the moisture level of the entire mix, starch included, remains low.

  "In terms of long-term storage, a high moisture content in conjunction with an acid may result in starch hydrolysis. That reduces viscosity," points out Sullivan.

  Other effects vary with the type of starch. Tapioca and potato starches are resistant to oxidation and off-flavor development because of their low lipid and protein contents. Waxy corn gives a high level of clarity because it consists of amylopectin. Amylose-containing starches such as dent corn and tapioca provide opacity. Potato starch furnishes clarity without gloss.

  "Amylose, being linear, tends to be more subject to retrogradation, so a waxy type of starch will give a more creamy texture than those containing amylose," adds Sullivan.

  Gums. Although not used as extensively as starches, gums furnish viscosity, provide texture, suspend solids and perform other functions in dry mixes. Often they are used in conjunction with starch.

  Along with temperature of hydration, the dispersion method greatly affects gum selection. Many gums require high shear, which is typically not an option in home or even foodservice preparation. However, the requirements vary with the ingredient.

  "With cellulose-based products, there is no hydration required; it's simply dispersion so they can be used over a wide temperature range," notes Sharann Simmons, commercial development manager, FMC Corp., Food Ingredients Division, Philadelphia. It's important to choose these products based on the shear requirements. Some require a great deal of shear. Others have been developed to disperse in low-shear applications."

  If the gum is not dispersed properly, it will not develop significant viscosity. A slight thickening may occur, but without the correct technique the effect is merely that of the added solids -- something that maltodextrin could do much more cost-effectively.

  Other factors influence the performance of gums in dry mixes. Competition with starches or other ingredients can curtail hydration. High levels of acid can adversely affect how a gum goes into solution.

  "In certain products, salt inhibits hydration," warns Mark Freeland, director of advanced colloids, Rhône-Poulenc Inc., Cranbury, NJ. "Often it depresses the viscosity that can be developed. You would need to look for brine-tolerant products."

  By adding gums to a dry mix, a food product designer can vary the texture from that normally achieved with starches. Depending on the gum and the amount used, the resulting texture may range from gel-like to smooth but non-pasty. Hydrocolloids can promote cling in a sauce or similar mix.

  Proteins. Occasionally proteins are used in dry mixes to provide viscosity. Because they tend to be more expensive than other stabilizers, they generally serve additional functions, such as protein fortification or even fat replacement. They exhibit both hydrophilic and hydrophobic properties, so they not only have the capacity to bind water, but they also make excellent emulsifiers.

  As with other dry-mix ingredients, solubility of functional proteins drives the selection process. The solubility and dispersibility properties are related to the molecular structure and the types of interactions that occur with the protein.

  The proteins most often seen in dry mixes come from dairy sources: caseinates and whey protein concentrates (WPC). Sodium caseinates and, more notably, calcium caseinates furnish coffee whiteners with viscosity and opacity, while their emulsifying properties inhibit fat separation. Sodium caseinates act as emulsifiers and add foam stability and structure to bakery mixes. They also mimic the appearance and mouthfeel of milk in nutritional beverages and increase the perception of fat. Sodium caseinates are highly soluble, but calcium caseinates tend to form stable colloidal suspensions. Heating caseinates increases their viscosity.

  Whey protein concentrates can replace the functionality of dehydrated milk or eggs: emulsification, aeration and thermal gelation. Used in bakery mixes, they modify the texture of the finished product. Because they exhibit thermal gelation, they can add viscosity to products such as sauce mixes or cream soup mixes, especially those with an acidic pH. Without the application of heat, they exhibit low viscosity and can be used for protein fortification without a significant increase in viscosity. A number of modified whey proteins act as fat replacers.

  Like dairy proteins, soy proteins can perform the same functions in a dry mix as milk or eggs. Manufacturers offer a wide variety of products that display a range of functional properties -- gelation, emulsification and viscosity.

  Emulsifiers. While proteins or other ingredients provide emulsification properties, sometimes a dry mix requires ingredients whose primary purpose is emulsification. Often, adding emulsifiers in fat-based systems aids in the dispersion of the mix, reducing clumping and allowing all ingredients to remain evenly dispersed. Emulsifiers help maintain foam stability in products where aeration is required, such as whipped topping or dessert mixes.

  "Emulsifiers allow you to incorporate more air, but decrease the size of the individual cells," explains Joe Sigel, technical product manager, bakery, Danisco Ingredients, Grindsted Division, Industrial Airport, KS. "The smaller the air cell, the better the foam stability."

  Some emulsifiers are available in a flowable "beadlet" form that can be blended into dry mixes, but these must melt before they function. For low-temperature applications, fluid emulsifiers can be added directly to a mix by plating them onto the dry ingredients. Depending on the type or level of emulsifier, it can be sprayed onto the product or dripped in during mixing.

  Lecithin also can function as an emulsifier in dry mixes. It, too, can be plated, either alone or mixed with shortening. Alternatively, a powdered form of lecithin, can be used.

  Picture a beverage mix with about one-half gram of ingredients per package. What does that mean in terms of fill weight targets? How do you get the mixing instructions and the Nutrition Facts panel on the package? What happens if the consumer sneezes?

  Since carriers are meant to replace empty space, they should be economical, relatively inert, and have minimal impact on flavor, appearance and texture. The less complex the product, the more obvious the effect of any added ingredients will be. Historically, maltodextrins from different sources and, in some applications, dextrose or whey have fit the bill.

  As ingredient technology grows more sophisticated, the role of these ingredients shifts toward functionality. Maltodextrins, for example, give products varying degrees of viscosity, a useful trait when formulating without sugar. Carbohydrate-based sweeteners give slight, but perceptible, body to beverages. High-intensity sweeteners do not. So, not only does an ingredient like maltodextrin replace sugar's role as a carrier, it provides a little more mouthfeel by contributing solids. On the other hand, it may be necessary to minimize the impact of certain characteristics from the carrier.

  "In nondairy creamers, maltodextrins can serve as a co-carrier, co-opacifier, often in combination with a partially hydrogenated vegetable fat," says Brine. "However, it may also act as a fat substitute. If you take fat out of a product the flavor balance changes, so the absence of flavor in a maltodextrin becomes critical."

  For some beverages, clarity is an issue. Maltodextrins are soluble, but clarity increases with increasing DE (dextrose equivalent).

  Standard carriers or bulking agents can still provide a certain degree of functionality. If whey contains protein that confers some stabilization to the system, it certainly isn't going to change its nature because it's part of a carrier. Also, many of these ingredients have a propensity to bind water and influence the finished product rheology.

  "With maltodextrins, as DE increases, hydroscopicityity increases," says Sullivan. "A 5 or 10 DE maltodextrin will be relatively stable. Working with a 15 or 18 DE maltodextrin or a corn syrup solid, you may encounter problems with the products picking up moisture from the air. If you are formulating a cake mix or something using a fat replacer, you may actually want to incorporate a more hydroscopic material to hold onto the moisture and provide lubricity."

  Carriers serve one last function. In some dry mixes, to extend shelf life and preserve functionality, certain compounds should not come into contact with each other -- for example, acid leavenings and bases. Adjacent molecules can react, thus decreasing the amount of leavening available during product make-up. Encapsulation is an efficient, high-tech, but costly way to accomplish this. Dispersing the compounds throughout a dry diluent may not be as effective, but often it is sufficient for the application.

  "Ingredients with a uniform particle size can be used to improve the flow characteristics of a mix," suggests Sullivan. "A 10 DE maltodextrin that is spray-dried but not agglomerated can serve this purpose. It helps both the mix and the filling operation, minimizing bridging and helping the mix move consistently through the system."

  When functional ingredients provide insufficient moisture protection, anticaking ingredients such as tricalcium phosphate or silicates help keep products free-flowing. This is often the case when the mix contains highly hygroscopic materials such as cheese powders, corn syrup solids or hydrolyzed vegetable protein.

  "The hydrophilic nature of an ingredient is the main factor that affects its flow," says Paul Lucas, engineering associate, PPG Industries, Pittsburgh. "Silica has many silanol groups on the surface that want to bond with water to satisfy an imbalance in the structure of the silica. That's why it helps alleviate caking problems related to water."

  The particle size also influences the ingredient's effectiveness. A fine particle with an irregular surface exposes more surface area, but can pack tightly together. A spherical particle, like silica, with an open structure enhances flow by reducing friction while maintaining the area exposed to moisture. The porosity of the particle makes it act like a sponge to soak up relatively large amounts of oil or water. Several analytical tests indicate the absorption efficiency of the compound -- from sophisticated nitrogen absorption/desorption method to simple liquid absorption measurements.

  "A number of factors come to bear when choosing a flow agent: the composition of the product, even considerations such as whether or not the product is kosher," says Percie Lamar, Ph.D., market development manager, Flavorite Laboratories, Memphis, TN. "That may preclude calcium stearate. If a mix is all natural, you want a product that will reflect that on the ingredient legend."

  The FDA restricts the usage level of chemical anticaking agents -- 2% maximum for silicon dioxide, for example. Some have associated dusting problems. In other cases, they reduce dusting. Others just work better in certain applications.

  "For some reason, calcium stearate seems to be the only flow agent that works in onion and garlic powder," remarks Lucas. "Otherwise it is rarely used. It's expensive and, in most applications, doesn't work as well as silicates."

  Pasta. Standard pasta can be used in dry mixes, but because of its high moisture content (about 12%), it should be packaged separately from seasoning or sauce mixes. If not, the moisture from the pasta will migrate to the other ingredients, causing caking and potential microbiological problems. Products packaged together in a single unit require special low-moisture forms (about 6%).

  Instant products call for specialty pastas known as precooked and instant pasta. During cooking, pasta undergoes two processes: starch hydration and protein denaturation. As dried pasta comes into contact with boiling water, starch gelatinization occurs and the starch granules swell. At the same time, the heat denatures the protein. To manufacture pre-cooked pasta, the two reactions must be balanced to produce an acceptable taste and texture. The starch must not slough off and must remain in the protein matrix. The matrix must maintain its integrity.

  "Technologies for altering the cooking characteristics have concentrated on the starch hydration and gelatinization phase," says Sanford Wolgel, Ph.D., industrial sales, Conte Luna Foods, Philadelphia. "Pregelatinization of the pasta is usually accomplished directly after extrusion with steam. To dry this type of pasta, a variety of proprietary technologies have been developed, including freeze-drying and special dryers. Depending on the technology, the cooking times range from 90 seconds for instant pastas to 5 minutes for precooked pastas."

  Another type of precooked pasta suitable for instant dry mixes is couscous. Although the word conjures visions of some little-known grain, couscous is a form of pasta made of durum wheat and water. The wheat is mixed with water, formed into small granules, steam cooked, then dried. The dried granules are sorted by size into coarse, medium and fine grades. This yields precooked particles that can be reconstituted with hot or boiling water, or steamed, as is traditionally done in the Mediterranean.

  Rice. There are many varieties of rice from a crop standpoint, but crop variety is rarely a factor for ingredient selection. The major differences among rice products occur from processing. Processed rice products include brown, milled white, parboiled, quick-cook and instant. All may be used in dry mixes, depending on the application.

  "Everything now is geared toward convenience," says Frank Orthoefer, vice president, research and development, Riceland Foods Inc., Stuttgart, AR. "We are seeing more demand for products that cook up quickly."

  Cooking time is the major distinction between the various types of rice, but there are other differences that influence the selection of a particular kind. The cooked rice characteristics vary depending on the process used. The moisture contents also fall in different ranges.

  Regular milled rice takes 20 minutes to cook. It contains about 12% to 14% moisture. Brown rice takes about 40 minutes to cook. Instant rices are ready to eat in 5 minutes and the moisture levels are a few percentage points lower than milled. Making instant rice requires pre-cooking, which leaches off some of the flavors, creating a flavor different from milled rice.

  "We go through a standard instantizing process for some of our products, yielding what we call an instant or instant parboiled rice," says Orthoefer. "Basically, what we've done is open up the structure so the density of that kernel is reduced and it absorbs water very rapidly. It only really requires rehydration."

  Because the texture of cook-up rice differs from instant rice, one rice supplier recently developed a rice that requires a shorter cook time while maintaining the texture and appearance of regular milled rice. While not precooked, the texture of the rice has been expanded to promote rapid take-up of water. It remains fluffy and separate when cooked, retaining a firm texture, as well as the kernel integrity and flavor of traditional milled rice. This type of rice takes 7 to 8 minutes to cook. Because the bulk density is lighter than conventional rice, it provides advantages in packaging and shipping. In addition, the moisture is lower than that of standard rice so the new rice is more compatible with seasonings and will not promote caking.

  Producing rice for "just add hot water" mixes requires taking instant rice one step further. The rice needs a more open structure than standard instant rice in order to hydrate quickly without boiling. Freeze-drying or a similar process creates this porous structure.

  "One thing to remember when working with mixtures is that all of the ingredients need to cook up at the same time," says Orthoefer. "You want the rice to have the proper sensory characteristics, as well as the other ingredients. You don't want one ingredient hard and brittle while the rice is overcooked. There are ways we can actually adjust cook time for a particular application."

  "It's possible to adjust the moisture without affecting the quality of the finished product," adds Don McCaskill, Riceland's manager of rice research and development. "Lowering the moisture too far can potentially shorten the shelf life. Rice contains a small amount of fat that will oxidize faster than normal at extremely low moistures."

  Cheese and other flavorings. "There are many considerations when working with dry blends of seasonings and other ingredients," states Flavorite's Lamar. "One consideration is granulation to assure that the product flows properly. If the product is packaged in a container for multiple use, or a shaker bottle, hygroscopicity is another important factor."

  Many ingredients that are used to flavor dry mixes, especially those high in protein, readily pick up water, so it is also important to protect them before addition. Storing them in lower humidity areas and providing sufficient packaging helps prevent moisture pickup and subsequent problems. Moisture also accelerates many degenerative reactions.

  The relative humidity really impacts the shelf life of a flavor," observes Alan McFadden, manager, beverage R&D, McCormick & Wild, Hunt Valley, MD. "The lower the moisture content, the longer the flavors last. With citrus flavors it accelerates the formation of terpenes."

  Cheese powder appears in many dry sauce mixes. Most cheese powders are spray-dried, although some may be dry-blended with other ingredients. A cheese powder often contains whey, starch and other functional ingredients and fillers.

  "The industry typically sells cheese powders that fall into a wide price range," says Tom Rieman, product manager, Kraft Food Ingredients, Memphis, TN. "The primary difference is the ingredients. The original products were simply natural cheese with phosphate added that were spray-dried. Now the trend is to spray-dry process cheeses, those that contain whey and other ingredients, to make a more economical product. That trend is continuing and we are seeing more things like flavor potentiators or flavors that help save on the raw material costs."

  Most cheese powders do not supply functionality, except that which is directly attributable to the increase in solids or protein content. They primarily add flavor. The way the flavor comes across may vary depending on the application and the production method.

  "Many manufacturers make a slurry of the ingredients then spray-dry the mixture to get a homogeneous product," adds Rieman. "A dry-blended product in the same ratio gives you a different-flavored product."

  The fat content affects the flavor and the handling characteristics. More fat tastes better and improves mouthfeel, but it also can make the powder more difficult to handle. Fat content ranges from about 14% in blended powders to 38% for reduced-fat cheese versions to about 65% for spray-dried natural cream cheese. To prevent lumping, the temperature should remain below 85 degrees Fahrenheit during handling. It also helps to limit compression.

  "Cheese powders can be hard to wet, so it helps to use something to separate the particles," recommends Sullivan. "That's when you want to use some of the starches or maltodextrins."

  Vegetables. Vegetables and, occasionally, fruits enhance many dry mixes. They come in a variety of formats with distinctive properties: air-dried, freeze-dried, air/freeze-dried, puffed and infused.

  Air-dried products rehydrate slowly -- 7 to 15 minutes in boiling water, depending on the vegetable. Freeze-dried products rehydrate quickly, from almost instantly to about 3 minutes. The intermediate products like puffed vegetables take about 3 to 5 minutes. At temperatures below 190 degrees Fahrenheit, the process takes Ionger. Size also influences the hydration rate; the larger the piece, the longer the hydration.

  "Puffing is a process where you hit the product with high heat, quickly producing steam which expands the product," says Phil Schline, brand manager at' Basic Vegetable Products, Vacaville, CA.

  Freeze-drying is an expensive process. Using air in the initial stages to remove a portion of the water makes the process more cost-effective. Though they rehydrate rapidly, freeze-dried products are not appropriate for all applications. The cells are very open, which can accelerate oxidation, and freeze-dried products tend to fade rapidly. Packaging must provide an effective oxygen barrier or these products will deteriorate rapidly. The process itself drives off much of the flavor.

  "There is a misconception about freeze-drying: people think of it as a high quality product when it's really not. It's just used for a different application," explains Schline. "It's a harsh process. Freezing causes cell damage. Anything volatile is flashed off in the vacuum chamber during drying."

  Moisture depends on the process and, as with all dry mixes, the ingredient should fit with the total mix. If the moisture is too low, the piece may become brittle. If too high, it will accelerate deterioration. Less moisture migration occurs at lower water activities, so an infused piece can actually have a higher moisture content than other types without creating problems.

  Because these products are granular in nature, they tend to be difficult to disperse evenly in a dry mix. A two-stage filling operation can avoid the problem by keeping the large vegetable particulates and the finer seasonings separate.

  According to Schline, much of the flavor is lost no matter what the process. So except for the flavoring vegetables such as onions, dried vegetables primarily add visual appeal. Using a vegetable with a contrasting color -- red peppers, orange carrots -- can increase the impact, since most vegetables are green.

  Because dry-mix products are designed for the "average person," on average he or she will follow the exact directions. However, the range that produces that average may look like the Grand Canyon. Someone I knew opened a cake mix, dumped the powder in a pan, and proceeded to pop it in the oven. (At least the oven was on.) Knowing how the ingredients in a dry mix function and knowing their limitations at least gives the product a chance to shine.

  Agglomeration fuses smaller particles to create large aggregates. The particles are moistened so they adhere to one another upon contact. The process may vary somewhat. Typically, a controlled amount of steam or moist air is applied to the particles that are free-falling, conveyed by air or conveyed on a fluidized bed. The aggregated are then redried and cooled, and frequently are classified by size.

  Agglomerated powders maintain a large surface area for quick hydration. At the same time, they reduce the clumping that often results when small particles are wetted. This means that the particles must be fused to resist breakage, but not bound so tightly that they lose their open structure.

  "When a very fine, very soluble ingredient such as milk powder, is added to water it is so hydroscopic that it will immediately absorb water on the surface," explains Percie Lamar, Ph.D., market development manager, Flavorite Laboratories, Memphis, TN. "It actually seals the product, forming a lump. In agglomeration, you make larger particles that are actually less soluble than the powder. They will disperse throughout the liquid and then dissolve."

  Agglomeration also can modify particle size so that a mix is more resistant to separation. Particles in a blend with different sizes and bulk densities tend to separate out. By standardizing particle sizes with agglomeration techniques, the problem is minimized.

  Agglomeration can be done on individual ingredients or on the mix as a whole. "If you have an ingredient like salt mixed with something with a lighter bulk density, like cheese powder or whey, you can potentially get some separation," says Lamar. "You can spray-dry it together, then agglomerate, and the ingredients won't separate out."

  Spray-drying takes a liquid product and creates a dry form. This method is widely used to create powdered products and ingredients. In the process, an aqueous liquid, emulsion or paste is atomized into a drying chamber. This drives off the moisture, forming highly porous particles.

  The actual structure depends on a number of factors, including the ingredients used, the state of any emulsion, the size of the droplets formed, and the parameters and method of drying. Ideally spray-drying should result in a consistent distribution of the components throughout. As with agglomeration, spray-drying can involve individual ingredients, several ingredients or an entire mix.

  "In the flavor industry, gum arabic tends to be used for citrus flavors. Starches and dextrins are used in many of the other applications," says Mark Freeland, director of advanced colloids, Rhône-Poulenc Inc., Cranbury, NJ.

  These carriers act as diluents or carriers for a functional ingredient such as a flavor. Small amounts of the functional ingredient are dispersed throughout and coated by the carrier, resulting in a form of encapsulation. The matrix does not totally coat the other ingredient but it does increase the resistance of the product to deterioration, especially oxidation.

  "In dry mixes, spray-dried flavors are appropriate from a cost standpoint and certainly give good stability," says Alan McFadden, manager, beverage R&D, McCormick & Wild, Hunt Valley, MD. "You will lose some of the flavor notes during the process. Citrus flavors are inherently less stable, and the heat that is generated in the tower during drying drives off some of the volatiles. But there is such a short exposure time that the impact is minimal. Plus you can adjust the process and the carrier."

  Encapsulation. "Encapsulation allows people to combine ingredients that are reactive to other ingredients or to the environment," says Walt Zachowitz, product manager, Balchem Corp., Slate Hill, NY. "It prevents ingredients from degrading, such as vitamins and flavoring acids. It can control reactions like leavening, or products like yeast and mold inhibitors."

  "It can help companies develop products that in practical terms would otherwise be impossible," adds Scott Dardig, Balchem's national sales manager for encapsulates. "In a directly acidified sourdough bread mix, for example, encapsulated fumaric acid can protect the leavening and improve the volume and texture, but provide the characteristic taste."

  Although many people in the food industry consider spray-drying a form of encapsulation, the term often refers to other technologies that provide a more complete coating over the ingredient. A number of encapsulating materials can be used, depending on the product, the protection and the application. Most are fat-based, but some are carbohydrate-based.

  These determine the conditions that will release the active ingredient. Fat-based systems typically require some degree of heating and would not be appropriate for mixes reconstituted and used under cold conditions. Standard hot-melt coatings work in the range from 115 to 160 degrees Fahrenheit, but some special formulations can work outside this range.

  Encapsulation can provide a measure of tolerance for active ingredients, and it reduces variability. Encapsulated leavening does not react until heat is applied. This increases mixing and holding time tolerance. It protects the mix from reactions among different ingredients. Unprotected iron and vitamin C can react to form black specks, for example.

  Designers should recognize that encapsulated materials may act differently as part of the mix.

  "A glass-encapsulated product affords excellent protection to the flavor oils," says McFadden. "But because of the shape, you may not get the same level of attachment to other particles in the mix that you would with spray-drying. This could be a problem for products that receive a great deal of vibration or agitation."

  Still, the technology has evolved to the point where a lot of these problems can be addressed. If the material isn't performing in the desired manner, not only can the coating be modified, but changing characteristics of the substrate also may do the trick.