From improving texture to extending shelf life, starch is a key ingredient in many formulas.
While familiar plants provide us with the most common sources of food grade starch — namely corn, potatoes, wheat and rice — new sources occasionally do emerge to provide various functional and quality characteristics. Two polymers, amylose and amylopectin, comprise the main components of starch. The difference between the amount of these polymers various starches contain helps determine their functional use in an end product. For example, a high amylose starch might be used in an edible coating, while a waxy cornstarch with a high ratio of amylopectin to amylose is more of the non-gelling variety that forms viscous pastes when heated.
In sweetgoods, such as brownies, cookies and cakes, starches perform a number of useful functions. They can help replace eggs, reduce spread and increase volume in cookies; build cake batter viscosity; assist with moisture management in muffins, snack cakes and brownies during baking, which extends shelf life; act as an adhesion aid for glazes; provide air incorporation, build batter viscosity and improve mouthfeel for reduced-fat and fat-free muffins and cakes.
Cargill Texturizing Solutions, Minneapolis, offers a line of starches with lipophilic properties that function as emulsion stabilizers. Egg products in baked foods supply foaming, emulsification, coagulation, flavor and texture. A lipophilic starch works well in combination with eggs to partially replace whole eggs in cake formulations. One version is a cook up starch and the other available variety is a pregelatinized waxy maize starch. Combined with hydrocolloids, lecithins and emulsifiers (and sometimes soy flour) in functional blends, formulators can achieve egg replacement of 50 percent and more while retaining finished product quality. Soy flour is sometimes used for egg replacement in certain types of cookies as well as for moisture retention.
To maintain proper cake batter viscosity, Cargill recommends instant, pregelatinized starches. While individual starch choice varies widely depending upon the end product, in general, these starches will help set structure and control texture, increase volume and help retain moisture.
Some bakers choose a native starch for its clean label advantages, as modified starches do not necessarily meet the clean label profile many bakers seek. Starches are modified to improve functionality, impart stability caused by the pH of a system, and improve processing conditions (i.e. temperature, shear) and shelf life. They also are modified to alter the viscosity development during processing or in the final product.
“Baked goods requiring a ‘natural’ label can still benefit from native starches (not chemically modified) as well as combinations of native starch. Such products still positively impact batter viscosity, texture, moisture retention and shelf life,” says Sandy Nieman, senior food scientist for bakery, snacks and cereals, Cargill.
According to Nieman, “The key consideration for formulators selecting the appropriate starch is to consider the effect other ingredients might have on the starch. For example, acids break starch bonds. This accelerates gelatinization and viscosity breakdown. Sugars, gums and protein compete for the available water, but also complement structure support.”
Sugars impede the swelling of the starch granule and different sugars have different influences. The retardation of swelling and extension in the gelatinization range may result in both decreased viscosity and gel strength.
Fats and oils and emulsifiers coat the starch granules, which can delay gelatinization and hamper viscosity development. Modified starches can be prepared to withstand certain processing conditions and adapted to a degree to interact in a synergistic manner with other ingredients.
Grain Processing Corp. (GPC), Muscatine, Iowa, offers cook up starches and an instantly hydrating starch that enhances texture in a range of bakery products. By adding 5 percent instantly hydrating starch to their dry formulations, bakers can improve crispness in pizza crusts and increase chewiness in cookies without hampering spread. This instant hydrating starch also can be used as a tack coating or egg wash replacement.
GPC also offers intact granule starches that help provide stability in chemically leavened products, such as cookies, muffins, cakes and brownies. The intact granule holds onto moisture over time even through freeze/thaw cycles. “We have more than 18 months of shelf life studies on frozen cakes. These cakes show no signs of the cracking or shrinking seen in many frozen baked products today,” says Casey Lopez, associate scientist for GPC. These starches are resilient as well, and are able to withstand mixing, pumping, baking and freeze/thaw cycles.
Managing moisture to increase shelf life is always a concern, and the shrinking and cracking of products is often a result of over-stabilizing, Lopez notes. Determining the few key ingredients needed is the challenge. “Examine the formulation and add one thing at a time using moisture management tools. It helps keep the costs down and keeps the label simpler,” she adds.
Particle size can have a big impact on the dispersion and hydration rate of both pregelatinized (roll dried) and granular cold water swelling starches. This may impact mixing times, incorporation of particulates and depositing.
Granule size also affects starch blend properties, according to a new study published in Food Researcher International. The relative size of starch granules used in a blend could determine overall gelation behavior, in addition to determining whether or not the starch components add to each others' properties or interact to promote new ones. These granules are generally either small and spherical or large and ellipsoidal. Rice starch is relatively small in granule size (2 µm in dia.) compared to the average granule size of potato starch (48 µm in dia.).
Temperature also affects the starch granules. If the starch is cooled too fast in a freezer, for example, there will be a loose alignment of the amylose and amylopectin, resulting in a weak gel. If the mixture is cooled too slowly, there will be considerable alignment, and again a poor gel with a lot of syneresis.
Although most starches are relatively bland when fully cooked, they do have a flavor impact depending on starch selection. Some naturally possess cereal notes — potato and tapioca-based starches are most notably bland in nature. Starches also can affect how flavors within a product are released or developed. If experimenting with a new starch in a formulation, flavorings and spices might seem more intense. Other starches might mask top notes or delay flavor release.
Fresh or highly acidic ingredients used in a baking system can act detrimentally on a starch, so it is wise to think about a starch with acid tolerance.
By examining the entire baking environment, ingredient selection, ingredient order and processing methods and shelf life expectations, the proper starch selection will help create an optimum product.
The potential of grass pea starches
Polish researchers, in a study released in March, discuss the potential that exists for grass pea starches. Two varieties of grass peas are registered as growing in Poland, and the plant also is cultivated in Asia, Africa and southern Europe. The team studied gelatinization properties, pasting properties, flow and viscoelastic behavior and retrogradation.
Despite the availability of more common starches, new varieties offer the possibility of expanded functionality. According to the researchers, “grass pea starch may be an alternative for chemically modified starches and as a source of resistant starch, because of high amylose content and the resulting retrogradation susceptibility.”