Starch to the Rescue

Nowadays, food formulators are better able to achieve their objectives by capitalizing on the versatility of an ingredient such as starch, whether used in a more conventional manner as a thickener or stabilizer (in a batter or coating) or to meet current trends in achieving textural dichotomy, health and wellness, or organic standards. For instance, certain types of starch are particularly well suited for low- and non-fat applications, while others offer stability in refrigerated and frozen foods.

Starch varies nearly as much in source as it does in functionality. No matter the origin of the starch, it can be modified to fit a variety of applications. Physical characteristics differ from one type to another, ranging from grainy to smooth, heavy-bodied to light, opaque to translucent, and soft to firm gelled. Starch can be made to withstand freeze/thaw cycling, heat, mechanical shearing, and an acidic environment. Ingredient suppliers who offer technical assistance are in the best position to capitalize on the needs of product developers, who often are left with the difficult task of customizing formulas that meet their customers' rigorous demands.

An Evolution of Solutions

A brief back-to-basics review of starch only can benefit even the most seasoned and knowledgeable food technologist. Sources of starch include corn, rice, potato, tapioca and wheat. Two carbohydrate polymers--the linear chain amylose and the large, branched amylopectin--account for many of the characteristics associated with starch. Both polymers are composed of D-glucopyranose polymers, or the ring-form of D-glucose, linked by a-1,4 and/or a-1,6 glycosidic bonds.

Although carbohydrate chemistry can be rather complex, stated simply, amylose is a strong film-former with firm gelling properties, while amylopectin forms weak films and soft gels or is non-gelling. Starch varies in amylose and amylopectin, depending on its ingredient source. Dent corn may only contain 25% amylose, while high-amylose corn may have as much as 55% to 70% or more. Waxy maize, on the other hand, has less than 1% amylose content.

Some formulators turn to native starches when certain parameters such as a clean flavor release and a simple label are required. Native starches may be labeled as starch or corn starch--a consumer-friendly option for products destined for the “all natural” market. Native starches, which are available as a cook-up or for cold-water swelling applications, function as a stabilizer for items such as dressings and sauces, and as a dispersing agent for dry mixes. Organic-certified starches also are available to meet the needs of consumers who demand minimalist products that fill this niche.

Physical and chemical modifications give starch a multitude of characteristics. Agglomeration of a pre-gelatinized starch improves solubility in dry mixes. Cross-linking strengthens the starch granule, which increases resistance to shear. With an increase in gelatinization temperature, hot viscosity is reduced, and cooled viscosity is increased. Cross-linking is ideal for retort-type products, where good heat transfer is desired during cooking, but a thicker product results upon cooling.

Reacting starch with octenyl succinic anhydride yields a product with both lipophilic and hydrophilic properties--making a starch suitable for emulsification. Another type of substitution, produced via etherification or acetylation, results in starch that provides freeze/thaw stability. Starch slurries oxidized with sodium hypochlorite produce modified starches with enhanced binding properties ideal for use in batters and breadings. These oxidized starches gelatinize at a lower temperature than their unmodified counterparts, giving a lower hot viscosity and a cooled gel not susceptible to retrogradation.

Most product developers are well aware of starches designed for use as an economical and practical thickener or stabilizer, but technologists often stumble upon many other nontraditional uses as the need arises. For instance, modified food starches are used in food-based films, coatings, as carrying agents for active ingredients such as in breathable films, and as replacers for gelatin and animal-derived materials for capsules, notes Celeste Sullivan, senior applications scientist for a starch ingredient company. In addition, starch slurries serve as an adhesive for seasonings or other particulates that traditionally rely on oil for suspension

Solutions for achieving extended shelflife often fall to starch-based ingredients, particularly for bakery and dough applications. Certain kinds of modified food starch provide a moisture barrier for stability of refrigerated and frozen products, notes Sullivan. For example, substituted pregelatinized starches help retain moisture in baked goods, thus retarding staling and extending shelflife.

“Selection of a starch requires the formulator to recognize the product demands from idea concept to consumer,” says Sullivan. “The selection and performance also depends on other ingredients (i.e., solids, fats, gums and other hydrocolloids) used in the formula, as well as desired textural attributes.”

Roughing It

Various starches deliver textural attributes--not merely crunchiness, but creamy and crisp types as well. Some textural dimension may be attributed to starch, which acts as a coating or barrier protecting a substrate from moisture or oil migration. For instance, French fries typically contain a starch-based clear coating that imparts crispness to the outer surface, while maintaining a softer interior after frying. The coating also supports the shape of the substrate during processing.

A coating for a fried application may be composed of several different starches. For instance, modified corn starch provides an economical base, as well as a viscofier, for the batter. High-amylose corn starch and dextrin serve as a film former and deliver crispness; tapioca dextrin imparts adhesion and contributes to a coating's uniform appearance; and an unmodified, high-amylose corn starch imparts gelling and film-forming properties that produce a crisp surface, while preventing penetration of the frying oil.

Film forming is also an important property in foods where consumer expectations demand the substrate maintain its crunchy texture even when immersed in a liquid such as milk. Breakfast cereals, for instance, keep their crisp textures longer due to the presence of a starch-based film coating, notes Gil Bakal, managing director of a rice starch supplier. Special rice starches also can help control the crunchiness in extruded snacks, and the crispness in some baked products, thereby reducing breakage, adds Bakal.

A Healthier Approach

Much has been published recently in both consumer and trade media on the growing rate of obesity and diabetes in America. As a result, formulators are scrambling to deliver products that meet consumer needs for healthier foods. “A product formulator who is developing products with health and nutrition in mind will be looking for ingredients that not only help reduce fat, sugar and calories, but also build stability, shelflife and some required functionality,” says Sullivan, who cites examples of starch and its derivatives such as maltodextrin and polyglucitol (hydrogenated starch hydrolyzates) that help build viscosity, add mouthfeel and body, and provide freeze/thaw and steam-table stability in reduced-fat products.

Rice starch adds creaminess to low- and non-fat foods, and it can be used to replace milk fat in ice cream and other dairy products, notes Bakal. In addition, rice starch improves glossiness and stability in low-fat yogurts. Starch-based fat mimetics form gels that provide textural properties such as lubricity and mouthfeel similar to those exhibited by fat.

Food-safety related issues pose key concerns for product developers, with ingredient-induced allergens ranking high among possible considerations. Consequently, products targeted toward children often have stringent ingredient requirements. “Rice starch is among the most hypoallergenic of starches,” says Bakal, “and it is highly digestible, making it ideal for infants with few microflora.”

As consumers continue to develop an interest in functional foods, products designed for gut health become more prevalent. Resistant starch is not digested in the small intestine, but instead is fermented in the colon. Aside from promoting digestive benefits, type 2 and type 3 resistant starches help lower the glycemic response of foods after meals. Consumers are interested in learning about energy management and the maintenance of healthy blood sugar levels, and easily will understand the role resistant starch plays in promoting various health benefits, notes Rhonda Witwer, business development manager for the nutritional division of a starch supplier.

The versatility of starch continues to grow beyond the bounds of its traditional uses, from a thickener and stabilizer to a coating and film former to a fat mimetic and dietary fiber. Functional attributes such as improved flavor release, adhesion, dispersion and shelflife extension, among others, offer product developers many alternatives to meet the demands of current trends.

Going Global: Comforting Starch-based Dishes

For the Chinese, a soothing serving of congee; for the Irish, a warm bowl of oatmeal; and for many in Mexico, a calming cup of champurrado. Around the world, starch-thickened dishes and beverages offer inexpensive sources of nutrition and comfort.

Generally, such foods are based on gelling, starch-rich grains native to a region, grains such as rice, corn, millet or oats. Ingredients from tubers such as cassava or arrowroot also may be used to thicken traditional foods that are increasingly offered as processed prepared foods showcasing exotic seasonings and components.

For example, Mintel International's (Chicago) GNPD reports 78 new product launches around the world in the last half decade when searching for “congee.” In June this year, Fushun Bike Food Industry (Fushun, Lianoning, China) introduced “a congee said to be low in sugar and calories. It is enriched with calcium.” Its ingredient legend is populated with texture-providing components such as pumpkin, yellow bean, cereal, peanut kernel, arrowroot, glutinous rice, green peas, “flee-flower root,” Chinese yam and edible gum. (See product photo with squash on the label.)

In June, Nakashimato (Tokyo) launched a very differently flavored congee in the Singapore market. Under its Aohata brand, Benisake Gayu Salmon Congee includes rice, salmon, salt and yeast extract. Mintel reports that some nine of the 78 offerings make a “no-/low-/reduced-sugar” claim, many sweetened by sodium cyclamate.

As for champurrado, commercialization opportunities still lay ahead. Mintel's database finds such a product only from Juanita's Foods (Wilmington, Calif.). In 2004, the company debuted a version of the popular masa-thickened cinnamon, chocolate drink.