December 1, 1997

28 Min Read
Soup's On

 Soup's On
December 1997 -- Cover Story

By: Elaine Knehr
Contributing Editor

  Harried consumers often search the supermarket for quick, convenient, healthful and economical food products. They may end this search at the shelf, in the deli or in the freezer section as they discover what might represent the perfect food -- soup.

  Soup can be found in all these sections, processed and packaged to meet different needs. Cans and jars sit on the shelf awaiting the opportunity to provide a quick meal. Freezing delivers a fresher-tasting, more upscale product. Instant soups fit in a desk drawer for a quick lunch. Soup starter mixes provide a convenient base for a home-cooked pot of soup.

  A wide variety of soups entice consumers. Products range from clear broths to chunky stews to thick cream soups. This gives the food designer an abundance of ingredients to choose from when developing that next bowlful.

Get the (dry) goods

  Easy storage and convenient preparation make dry soups popular. Products include instant cup-of-soup, mixes that cook in 10 minutes or less, and starter soups requiring 25 minutes to prepare. The consumer wants a high-quality product with simple preparation. To provide this, the designer must consider the functionality of the ingredients and how the soup will be reconstituted.

  "Dry soups are used largely for dips and as a cooking aid in the United States," says Sean McCormack, senior food technologist, CPC Foodservice, Franklin Park, IL. "French onion, vegetable and spinach are popular. A dry soup is basically composed of four components. These are the suspension component, a bulk filler, flavoring and particulates. The target moisture level is 4%."

  Suspension ingredients provide thickness, and influence the texture or mouthfeel of a soup. Starches, flour and gums perform this function. The method of reconstitution greatly influences the type of thickener used; instant soups require a pregelatinized starch rather than a cook-up starch for example.

  Maltodextrin is a widely used bulk filler. In dry soups, this carbohydrate also functions as a processing aid and anti-caking agent. "Maltodextrin helps disperse the different-sized granule particles," explains McCormack. "A more uniform-sized distribution helps prevent bridging during filling. Maltodextrin is also a moisture sink. It absorbs moisture and minimizes caking.

  "Maltodextrins provide some opacity, mouthfeel and viscosity to soups," he says. "Modified maltodextrins can give a fat-mimetic mouthfeel to a dried cream soup."

  Numerous ingredients contribute to the flavor of a dry soup mix: herbs, spices, spice blends, flavoring, yeast extracts, hydrolyzed vegetable protein (HVP), monosodium glutamate (MSG) and salt. These ingredients are blended with the suspension and bulk-fill agents to improve dispersion.

  Particulates add visual and textural interest to soup. Ingredients include vegetables, meat, pasta, rice and beans. Ideal products have low moisture levels to maximize shelf life, and minimize moisture migration and clumping. They must fully hydrate within the specified preparation time.

  Dry-blending aims to assure uniform consistency of a soup mix. A great deal of physics and particle dynamics come into play. The amount and type of ingredients, the order of their addition, plus the mixer itself, all contribute to how thoroughly the product is mixed. For every product in a given mixer, there is an optimum mixing time and rate.

  Filling a dry mix into a package depends on the product formulation and ingredient selection. It is important to control particulate size and bulk density. Similar-sized ingredients are blended together to facilitate filling. Large particulates could be filled separately to ensure uniform distribution.

  The key is to keep the mixture free-flowing, and maintain a consistent fill rate. Ingredient density, moisture level and fat content impact the filling operation. For example, high levels of hygroscopic HVP encourage clumping, suggesting a low formulation level.

  Fat is a good news/bad news ingredient. It adds a desirable mouthfeel to cream soups. Fat also minimizes dusting when added to the dry mass, and improves product flow. Herbs or spices may require oil coating to prevent them from becoming airborne. The bad news is that caking potential increases at high fat levels. Also, oxidation can occur during storage, so it might pay to use a high-stability oil.

  The choice of using a liquid or "dry" fat depends on the available equipment and the desired end product. The fat should be evenly dispersed throughout the dry mass. Fat characteristics, such as melt point, affect the sensory attributes of the prepared soup.

  Anti-caking ingredients improve product flow. Powdered cellulose and silicon dioxide are two hydrophilic agents that alleviate caking problems related to water. The U.S. Food and Drug Administration restricts the usage level of chemical anticaking agents -- 2% maximum for silicon dioxide, for example.

  Agglomeration can improve dry soup mixes. This process impacts hydration rate, dispersability and particle separation. Agglomeration fuses smaller particles to create larger aggregates. The large surface area hydrates quickly. At the same time, it reduces the clumping that often results when small particles are wetted.

Can it!

  The concept behind retorting is to extend shelf life by heating foods prone to microbiological spoilage in hermetically sealed containers. The goal: commercial sterilization, which is defined as the inactivation of organisms of significance to both public health and spoilage under normal conditions of storage.

  Commercial sterility is achieved when the entire food mass undergoes the required temperature for the required time. The rate of heat transfer in a product is influenced by the type of process, equipment design, the size and shape of the container, product viscosity, particulates and headspace.

  Product composition influences the heat-transfer process. Solid pack foods, such as concentrated soups, are heated by conduction. Convection heating involves movement in the mass being heated. Chicken broth is heated by convection. A stew, which contains free liquid and solids, would increase in temperature by a combination of convection and conduction heating.

  For conduction-heated products, the center of the container is the slowest heating point. The time it takes this point to reach the thermal processing temperature -- the come-up time -- is significantly longer than for products employing convection. An extended heating time affects product quality, usually adversely. Quality is often improved by retorting at a higher temperature with a shorter exposure time. Formulation ingredients, such as thermally reversible gums, can assist in decreasing retort time.

  Soups are commonly retorted in cans or glass jars. Some concerns in choosing a package are cost, appearance, product compatibility and the retort itself. For a complete report on retorting, see "In the Can, A Look at Retorting," August 1994 Food Product Design.

A cold approach

  Freezing delivers a food product with better organoleptic and nutritional qualities, when compared with some other types of preservation, such as retorting. Most food-spoilage organisms cannot grow at frozen-food storage temperatures, and a reduction in their numbers might occur.

  Good manufacturing practices (GMPs) "are critical when making frozen soups," stresses McCormack. "Low microbe levels are needed going into formulation."

  The quality of a frozen food is affected by the treatment it receives prior to freezing, how it is frozen and subsequent frozen storage and thawing conditions. "Frozen soups are not heated as strenuously as retorted products," McCormack says. "A broth can reach 200°F. Cream soups are pasteurized to minimize burning and oxidative reactions during storage. Higher quality soups can be prepared with lower cook temperatures."

  Freezing rate also influences quality. Large ice crystals are formed with slow freezing, while fast-freezing produces smaller crystals. Smaller ice crystals generally mean less initial damage to ingredient structures, including particulates and starch granules.

  Soups are filled, cooled and frozen, according to USDA guidelines for frozen manufacture. The bags can be frozen, boxed and cased, or the packages can be frozen in the case. USDA requires that the product temperature drop from 130°F down to 80°F in 1.5 hours. A further reduction from 80°F to 40°F must occur in five hours.

  Freezing the bags before boxing presents some problems. The packages must maintain their shape. Frozen bags are brittle and can be damaged during handling. Freezing the case after packing with the chilled pouches minimizes handling. Chilling lowers the amount of heat that must be removed. Otherwise, any product at the center of the case will take significantly longer to freeze than that near the surface.

  Product quality can be altered during storage and distribution. Freeze/thaw cycles occur with temperature fluctuations. The ice crystals form, then melt, then refreeze, and so on. Undesirable effects include dehydration, syneresis, and the formation of large ice crystals, resulting in structural damage. Proper formulation and adequate packaging help minimize these issues.

  But when it comes to soup, as in so many other foods, one must start at the source. No amount of packaging finesse can compensate for a lack of quality ingredients.

Parts of the whole

  Soup is considered healthful for a good reason: Many soups contain vegetables, which are low in fat, contain dietary fiber, and provide vitamins and minerals.

  The type of vegetable used in a soup is influenced by the end product. Dry soups require dehydrated vegetables for shelf stability. Frozen soups use fresh or individually quick-frozen (IQF) vegetables to achieve good color, flavor and texture. Retorted products incorporate fresh, IQF or dried ingredients, depending on the economics and the desired end quality.

  "Dried vegetables are convenient, and provide a reliable source of supply," says Fred Turkovich, product manager, Basic Vegetable Products, Suisun, CA. "(The dry vegetable industry) started so manufacturers could extend their runs throughout the seasons, and eliminate waste and spoilage."

  Different methods of producing dried vegetables result in products with varying attributes. Vegetables used in dry soups include air-dried, air/freeze-dried and puff-dried.

  Air-dried vegetables are available in a range of sizes. "Common sizes are diced, granules and powders," Turkovich says. "Pieces can be a 1/4 in. or 3/8 in. dice. A typical powder would specify a maximum of 5% on a #60 U.S. screen, with the remainder passing through. The size used depends on the application.

  "An air-dried dice could be used in a retorted soup," he says. "The vegetables have a hydration rate of 10 to 20 minutes. Carrots, especially, hold up well during hydration and cooking. An air-dried vegetable powder gives color and flavor to a product, but no texture. Powders are useful in instant soups. They hydrate quickly and provide good flavor.

  "When comparing the cost of fresh to air-dried vegetables, it is important to look at the reconstitution factor. This indicates what the weight of 1 lb. of dried product is equivalent to on a fresh, prepared basis. The value varies depending on the vegetable. For example, 1 lb. of air dried bell peppers equals 10 lbs. of fresh, prepared peppers. When the handling of fresh vegetables is considered, air-dried vegetables are cost-competitive."

  Air-dried vegetables have a 5%-to-8% moisture content. They would typically be used in dry mixes that cook in 10 minutes and longer-cooking soup starters. Hydration rate is influenced by the cut or granulation. A thin slice rehydrates quicker than a thick cut, a granule is faster than a dice.

  Instant soups and cup-of-soups require quick hydration. Air- and freeze-dried vegetables are manufactured by partially air-drying the vegetable and then freeze-drying. The vegetables have a "moisture level of about 3.5%," Turkovich says. "With a hydration rate of one to three minutes, they are popular in instant soups. Air Freezô dried vegetables compare favorably to freeze-dried products. The color, flavor and texture of Air Freez dried vegetables are a little better than freeze-dried. And the cost is usually less." Freeze-dried items have the advantage of instant rehydration.

  Another product useful in cup-of-soups and instant soups is puff-dried vegetables. "The drying process causes the piece to puff back out close to its original shape," Turkovich says. "There are a couple of advantages to this product. It rehydrates quickly in three to five minutes. And the pieces float after rehydration, which improves the appearance of the soup."

  Fresh vegetables may be blanched prior to addition to soup. Blanching is a heat treatment that destroys enzyme systems, fixes color, reduces microbial population, and expels gas from tissue. If enzyme systems are not deactivated, flavor and texture deteriorate during long-term storage. Vegetables with a low microbiological load are especially important in frozen soups.

  "IQF or fresh vegetables that have been cut to specification are used in retorted and frozen soups," says McCormack. "Dried vegetables don't give the same flavor, mouthfeel and appearance as fresh. Even if a fresh vegetable gets soft in a can, the flavor is still there."

Spilling the beans

  Consumers' interest in foods that are "good for you" has enhanced the role of the lowly bean. "Beans have a good nutritional profile," says Rebecca Krueger, Ph.D., technical services director, Brown's Best Foods, Lincoln, NE. "They are typically low in fat, and contain 21% to 25% protein. They are a substantial source of some minerals, such as iron, zinc, phosphorous and potassium. One-half cup of cooked beans contains 4 to 7 grams of dietary fiber."

  The Nutrition Labeling and Education Act of 1990 states that foods labeled a "good source" of total dietary fiber must provide at least 2.5 grams of fiber per serving. Depending on the bean used, a soup containing one-fourth cup of beans per serving could trigger a fiber claim.

  Beans are available in many varieties, including navy beans, white beans, Great Northern, small red, pinto, and kidney.

  Retorted and frozen soups often use unprocessed dry beans. The Federal Grain Inspection Service specifies that dry beans may contain up to 18% moisture. The beans need to be hydrated before being added to a formulation. This involves overnight soaking and blanching, or precooking before use. Plant space is needed to accommodate bean processing.

  Canned kidney and pinto beans can be used in frozen chili. The bean juice gives viscosity and the mouthfeel of beans.

  Precooked and dried beans offer the convenience of directly adding the ingredient to the cook kettle. Krueger states that "a quick-cooking bean can be used in retorted soups and stews. The beans have a 20-to-35-minute cook time." Formulation plus retort time is sufficient to hydrate the beans.

  Precooked beans have an average moisture content of 8%, which is compatible with dry soup products. Preparation instructions influence bean choice. Beans range in cook time from 15 to 35 minutes. Instant dehydrated beans are used in cup-of-soup products. The beans hydrate with boiling water, followed by a 5-to-7-minute steep.

  Bean powder has application in both retorted and dry soups. "Bean powder can add thickening and flavor to soups," Krueger says. "Usage level ranges from 5% to 10%, depending on the desired viscosity. Partially cooked powder is often used in retorted soups. It is best to add the powder to other dry ingredients. This mixture is then stirred into, preferably, cold water with good agitation before bringing up to temperature. Instant powder is used in soup-cup applications. The powder hydrates in a boiling-water steep."

  Bean powder can be combined with starch to thicken a soup. Although the bean ingredient is more expensive than starch, "bean powder" can be appealing on an ingredient statement.

'Meating' the demand

  Meat contributes desirable flavor and texture to soup. A number of forms allow meat to be added to just about any soup product. Beef and chicken powders impart background notes economically. For visuals in dry soups, meat particles are freeze-dried or dehydrated.

  Flavored and formed freeze-dried meats hydrate quickly in instant soups while maintaining meat characteristics. "Dehydrated ham and bacon bits are found in many dry soups," says Steve Williams, section manager, flavor technology, Kraft Food Ingredients, Memphis, TN. "The shelf-stable pieces have a 5%-to-7% moisture level."

  Retorted and frozen soups utilize raw or IQF meat products. Beef, for example, is available diced raw or precooked and diced frozen. Formulated chicken pieces are an economical alternative to diced chicken.

  "Beef and chicken are typically size-reduced and then fully cooked in large stock pots," Williams says. "Soup is then formulated using the soup stock and cooked meat. Meat flavors and enhancers are widely used in soups. The strength and flavor of soup stock is difficult to control. Meat flavors standardize the flavor strength. Vegetarian-type flavors impart savory and meat notes in soups without meat. This appeals to consumers who avoid meat, but still like meat flavor."

  The opportunity exists to flavor meat particles used in retorted and frozen soups, Williams says. "Meat can be marinated, braised and then added to the soup. Interesting flavor profiles are possible."


  Cheese adds flavor to soup -- either predominantly or subtly -- and plays a role in the body and texture of soup. Dairy-based soups offer a desirable creamy texture to consumers.

  "Cheese-based soups can be formulated with natural cheese, processed cheese, cheese powder, cheese concentrates and cheese flavors," says Tom Rieman, product manager, Kraft Food Ingredients, Memphis, TN. "Food designers can mix and match to get the best flavor at the desired cost. Cheese powders have changed over time from a simple spray-dried cheese to a broad line of products that meet different requirements. Powders might have whey, dairy components or flavors added. Fat content varies from almost none to over 50%. Cheese powders are an important source of flavor in a product."

  Cheese powders work well in dry soup mixes. At a moisture level typically less than 4%, the powders are flowable and hydrate easily.

  "Retorted cheese soups are difficult," Rieman says. "Processing temperatures cause color change, loss of flavor and burning of the cheese. Natural and processed cheeses can be used if levels are kept low. Low-lactose cheese products help minimize browning. A high cheese solids powder can be combined with a cheese concentrate. The concentrate reduces the amount of powder needed."

  Because the heat limits the level, retorted soups often need flavor enhancement beyond the actual cheese used. This can be achieved with cheese ingredients processed to deliver greatly enhanced flavor profiles, such as enzyme-modified cheese. Yeast extracts, HVPs, MSG and salt also potentiate cheese flavors.

  "High-quality cheese and dairy-based soups are easier when the soup is frozen," McCormack says. "Lower cook temperatures minimize browning. Other dairy ingredients, like milk, cream and sour cream, improve the organoleptic quality of the soup. Dry-mix cream soups can achieve a creamy mouthfeel by using xanthan gum and starch. The gum provides creaminess without a starchy texture.

  "Non-fat dry milk or whey protein concentrate also impart body," he says. "Powdered cream or nondairy creamers provide fat background notes. Milk can also be added as part of the consumer preparation."

Carbohydrate loading

  Athletes are not the only people adding carbohydrates to their diets. Pasta and rice, which are predominantly carbohydrate, are sensible additions to soup.

  Pasta. "Pasta can be customized to meet the needs of the processor," says Mark Vermylen, vice president, A. Zerega's Sons, Inc., Fair Lawn, NJ. "It is important to work with the pasta manufacturer to achieve a pasta with the desired size, shape and functionality."

  Instant soups require pasta that does not need to cook in boiling water, but will hydrate in boiling water. "An instant, precooked pasta is used for cup-of-soup products," Vermylen says. "With a thickness of 0.020 to 0.025 in., the noodles hydrate quickly in boiling water. Typically, the moisture level of the pasta is 9%, but it is possible to reduce the amount to 6% or 7%."

  Standards of identity for several macaroni and noodle products are defined in the Federal Register (CFR 21, Part 139). Egg noodles, for example, must contain a minimum of 5.5% egg solids. "Many products are outside the realm of standards," Vermylen says. "Labels simply spell out the exact ingredients in the pasta."

  As pasta is subjected to more strenuous preparation or process conditions, changes are made in the thickness and formulation ingredients. A plain macaroni product with a 0.30 in. thickness is suggested for a dry soup that cooks in a few minutes. Longer-cooking soup starter mixes and retorted products benefit from 0.040 to 0.060 in. thick pasta.

  "Pasta is made with a maximum wall thickness of about 0.060 in.," Vermylen says. "A thicker pasta is harder to dry, and there is a risk of checking or cracking the pasta."

  Pasta is further strengthened by adding whole egg and, at times, additional egg white. The added protein firms the pasta and slows the cook time.

  "Frozen soups are usually designed for foodservice use," Vermylen says. This can put a burden on the ingredients. In addition to freeze-thaw concerns, "the soup must hold up on a steam table; 2% albumen is commonly used to help maintain shape and texture during freeze, thaw and cook. Pasta added to retorted soups is generally made with higher ingredient levels. Up to 7% egg white is used."

  Formulating pasta with the emulsifier glyceryl monostearate improves cooking performance by reducing starchiness and stickiness. Pasta maintains a firm texture during retorting and on a steam table. Alginate, which functions similarly to egg white, also is used to help maintain product quality when long holding times are involved.

  Vermylen recommends small pasta shapes for all soup products. Small forms allow for expansion during cooking. They also hold their shape better and look more appealing.

  Rice. "Rice is a very economical ingredient; 1 lb. of dry rice yields about 2.5 lbs. after cooking," says Don McCaskill, director, R&D, Riceland Foods, Inc., Stuttgart, AR.

  Processing alters the hydration rate of rice by changing its density and porosity, which influences how water penetrates the kernel. "Instant rice is precooked, and then dried at a rate that creates porosity," McCaskill says. "The texture and appearance differ from regular cooked rice. Instant rice is ready to eat in five minutes."

  For a soup that is designed for a slightly longer cooking time, using a product called quick cooking rice will yield a finished product with improved characteristics. According to McCaskill, "Quick cooking rice is heat-treated to create porosity. This reduces preparation time, yet the cooked product is similar to regular milled rice. Quick cooking rice simmers from six to eight minutes."

  To hydrate quickly without boiling, rice used for "just add hot water" soups requires a more open structure than standard instant rice. Freeze-drying or a similar process creates this porous structure.

  Rice is readily formulated into dry soup mixes. The moisture level is typically 12% to 13%, but rice can be dried to less than 8%.

  "Regular milled rice cooks in about 15 minutes," McCaskill says. "Soup starter mixes may take 25 minutes to prepare. And the process requirements for canned products often overcook regular rice. Parboiled rice helps prevent a too soft texture and loss of kernel integrity."

  Parboiling eliminates the air in rice, resulting in a more dense grain. This slows the penetration of water into the kernel. Parboiled rice cooks in 20 to 25 minutes. The rice is firmer with more separate grains. In addition to withstanding processing stress, parboiled rice better tolerates a steam table.

A pinch of this ...

  Homemade soup simmers on the stove top, the ingredients blending over time into a delectable dish. Commercial processing may not have the luxury of a long simmer to develop flavor, but can use a wide variety of flavorings instead. Commercial soups can be seasoned with spices, spice extractives, flavors and flavor enhancers.

  Dry spices are available finely or coarsely ground, whole or cracked and as various-sized particulates. Parsley flakes or other dry herbs provide visual appeal to soup. Dry spices have disadvantages: their flavor strength may vary or be weak; or they may darken during retorting. Because freezing will not kill bacteria, low microbiological counts are needed.

  To overcome some of these problems, designers can turn to other spice-derived flavorings. Spice extractives are natural liquids (essential oils, oleoresins and aquaresins) and spray-dried powders. Extractives provide more consistent flavor development than dry spices. Spice extractives are labeled as natural flavors, natural flavorings or spice extracts. Oil-soluble oleoresins possess the full flavor, aroma and pungency of fresh or dry spices. Aquaresins are oleoresins dispersible in water only or oil only. If both water and fat are present, the aquaresin will disperse in both phases. This makes them convenient to use in water-based foods, like soup.

  Other added flavors address specific product needs. An example of this is chicken-broth replacers. "Frozen chicken broth can be difficult to handle," says John Bauman, vice president, culinary food science, Wild Flavors, Inc., Cincinnati, OH. "For one thing, it must be melted before use. Chicken broth replacers are easy to use. The dry ingredient is mixed with water. A 2.5% solution can replace 2X chicken broth. The cost is less and handling is easier."

  Soups made with meat often contain a low level due to cost restraints. This requires added flavors to boost the meaty background. Meat and vegetable flavors are typically used at a level of 0.25% to 0.75%. More volatile flavors, such as garlic, are usually stronger and have a lower usage level.

  "Retorted soups use flavors created by reaction chemistry," Bauman says. "The flavors are stable, because they are produced by a heat-processing system. And the flavors are natural. Reaction flavors can be added at the beginning of the batch. Volatile flavors are best added right before the product is put into the can.

  "It is possible to develop more flavor during retorting. Brown notes can appear. If a roasted chicken flavor is desired in a retorted soup, (the food designer) might use a brothy chicken flavor. In a dry soup, it might be better to simply use a roasted chicken flavoring."

  Flavor enhancers potentiate the flavor of a food. Enhancers used in soup include yeast extracts, HVP and MSG.

  MSG, the readily soluble salt of glutamic acid, has long been a popular, albeit controversial, flavor enhancer. Research indicates that glutamate contributes to "umami," a fifth taste sensation linked to a full, robust and savory flavor. More on MSG is found in "Filtering the Facts on Flavor Enhancers," February 1994 Food Product Design.

  "Yeast extracts contain naturally occurring 5'-nucleotides," says Tom Gray, group leader, Applied Technology Laboratory, Red Star BioProducts, Milwaukee, WI. "The 5'-nucleotides potentiate flavor without contributing a flavor. HVP enhances, but also contributes, a meaty note. These ingredients are used at a rate of 0.05% to 0.25% as consumed."

  Flavor enhancers blend well with the other dry ingredients in instant and dry soup mixes. "Yeast extracts and HVP are hygroscopic," Gray says. "However, the enhancers contain 4%-to-6% moisture. At the level used in dry soups, the enhancers do not grab much moisture. Problems can occur if the package lacks integrity."

  Since enhancers potentiate what is present in a soup, it is possible to use less flavoring. Adding yeast to a reduced-cheese soup boosts the flavor and might improve mouthfeel. Enhancers can round out the flavor of a food. Gray explains that "yeast extract mellows an acid bite. Tomato soup tastes richer and creamier. If starch is masking flavor, yeast extract can compensate by bringing up the flavor."

The thick of things

  Consumers would find unappealing a watery stew or a cream soup with fat separation. To combat these types of problems, food technologists use hydrocolloids as thickening, stabilizing and suspending agents in soups.

  Starches. Starch sources include waxy corn, dent corn, potato, tapioca, rice and wheat. Starch characteristics are influenced by the source as well as processing. The viscosity of native potato starch, for example, is thicker than the other unmodified starches.

  Starches can be modified by cross-linking and substitution to improve their performance. For thickening applications, starches may be cross-linked or dual-modified, both cross-linked and substituted. Cross-linking reinforces the granular structure of the starch, enabling it to withstand the temperatures and mechanical shear of processing. This modification ensures viscosity, stability and desirable smooth texture. Substitution enhances the water-holding ability of the starch. This improves the storage stability of the product by minimizing retrogradation. Retrogradation occurs when starch chains begin to reassociate, squeezing out water and causing syneresis.

  Dry soup mixes can employ either cookup or instant starches, depending on the cooking required during consumer preparation. Key starch requirements include ease of dispersion and ease of cooking. Instant starches, which hydrate very quickly, may be physically modified via agglomeration to improve their dispersion and wetting properties.

  A dual-modified starch is useful in frozen soups. Cross-linking ensures granular integrity through the cooking phase. Substitution enables the starch to resist retrogradation throughout temperature fluctuation during frozen storage.

  Starches are used in retorted soups to impart thickening, and, in specific applications, to function as a can-filling aid. Soups containing particulates benefit from a can-filling starch. The starch thickens during the initial cooking to provide suspension viscosity during mixing, pumping and can-filling operations. Retorting breaks down the starch to give little, if any, viscosity in the finished product. A retorted soup might use two starches. A can-filling starch would function as a processing aid. A dual-modified starch would provide finished product viscosity.

  At high use levels, starch may mask subtle flavor notes in soup. To minimize masking, processors should use only the amount of starch that is needed to achieve the desired function. The starch needs to be optimally cooked to avoid starchy flavor and to ensure proper functionality.

  Cream soups are often formulated with wheat flour and modified starch. Typically, wheat flour is used in cream soups to impart flavor, opacity and some thickening. Wheat flour is low in viscosity, so a dual-modified waxy starch is used in conjunction with the flour. The starch gives the desired viscosity, and limits retrogradation and syneresis of the flour.

  Gums. Gum products include guar, locust bean, carrageenan, gum acacia and cellulose-based gums. Structure and functionality vary depending on the source.

  "Gums can replace up to 60% of the starch in a product," says Florian Ward, vice president, R&D, TIC Gums, Belcamp, MD. "For example, a product made with 1% gum holds more water than 5% starch. Solids are reduced, but the viscosity of the product is maintained. If gum is used alone, the consistency would be unappealing. Ideally, a combination of starch and gum is used."

  Gums can cost more than starch. Economies are realized in the lower usage level and by taking advantage of any synergistic effects. "Starch can mask flavor," says Jeff Dopf, marketing segment manager, FMC Corporation, Philadelphia. "Gums give a cleaner flavor release. By replacing some of the starch with a product like carrageenan, less added flavor is needed. Formulation cost can be reduced."

  Gums provide a number of advantages. Their water-binding properties impart freeze-thaw stability to frozen soups and prevent the formation of large ice crystals.

  Microcrystalline cellulose contributes opacity to soup. "This is a benefit when making a cream soup," Dopf says. "Microcrystalline cellulose makes the soup look whiter, and contributes to mouthfeel and body. Usage level is 0.3% to 1.0% in soup."

  "Most gums contribute opacity; carboxymethylcellulose (CMC) can give clarity to a soup," Ward says. "This is useful if a clear broth needs thickening. And while most gums are natural, CMC is not. It receives a chemical treatment during processing."

  Using gums also can aid soup processing. Thermally reversible gums can act as can-filling aids in retorted products. These gums lose viscosity at higher temperatures, but return to the desired thickness upon cooling. Some thickening occurs in the cook kettle, helping to suspend particulates as the product is filled. High temperatures during retorting then reduce viscosity. "The lower viscosity improves heat penetration," Dopf says. "Cook time can be reduced, resulting in a better end product and increased productivity."

  Iota-type carrageenans are gums that are thermally reversible and thixotropic. "Thixotropy is the ability of a gum to be fluidized by agitation or shear," Dopf says. "When shear is removed, the gel returns to its original, higher viscosity."

  In a canned soup, pumping provides shear. The attendant lower viscosity makes filling easier. A rotary retort, which provides constant agitation, keeps the viscosity low.

Making a reduction

  Health-conscious consumers are on the lookout for low-calorie, reduced-fat and low-salt products. Soups can be formulated to address these concerns.

  Cream soups are the most likely target for fat reduction, since broth and vegetable soups tend to be low in fat. "Gums maintain viscosity in a soup with a lower level of solids," Dopf says.

  "Carrageenan and cellulose provide the thickening and mouthfeel that are key to low-fat products."

  Low-fat and no-fat soups require adjustment in flavoring. "Some flavors are carried by fat," Bauman says. "When the fat is removed, flavor diminishes. Some chicken and beef flavors are made with a fatty profile that gives the perception of fat in the mouth. As fat is removed, flavor release changes. It is possible to use less flavor. Without the fat, flavor may release quicker."

  The major contributor of sodium for most soups is salt. However, reducing salt in soup also reduces the flavor impact. The challenge is to replace an inexpensive ingredient while maintaining a good flavor profile. The many flavor enhancers are often used; they might contain some sodium, but the usage level can be significantly lower. In addition, vegetable powders and additional spices and herbs can improve the flavor of a reduced salt soup, but tend to increase product cost.

  "Yeast extract can increase the perception of salt and other savory flavors associated with salt," Gray says. "The extracts tend to enhance onion, garlic and spice notes. In a soup containing some potassium chloride, these flavors could be enhanced more than the bitterness."

  Soup provides nutrition, taste and convenience, offering possibilities for wide consumer acceptance. But every step along the food product design path is vital to ensuring that when the "soup's on," it's been worth the wait.

  Free-lance technical writer Elaine Knehr holds a bachelor's degree in food technology and a master's degree in business. Her 10 years of experience in product development covers a wide range of food products.

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© 1997 by Weeks Publishing Company

3400 Dundee Rd. Suite #100
Northbrook, IL 60062
Phone: 847-559-0385
Fax: 847-559-0389
E-mail: [email protected]

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