The baking process is the final step of breadmaking, transforming dough into expanded bread, with the resulting crust color associated with aroma, texture, and appearance, which are important characteristics to consumers. Baking requires very high temperatures, typically between 160 and 250 °C. Although protein receives the most attention when it comes to describing flour quality, it is important to remember that flour is made up of nearly 70-80% starch.

Starch is a versatile and essential component in breadmaking and baking. Its unique properties contribute to the structural integrity, texture, moisture content, and overall quality of a wide range of baked goods. Different sources of starch, such as wheat flour, contribute distinct characteristics to the final product, allowing bakers to achieve various textures and flavors in their creations.

The science of starch

Starch is a macronutrient in several foods and supplies 50 to 80% of the calories consumed by most of the world’s population. Starch is synthesized in the plastid of plant cells through a series of complex biosynthetic pathways controlled by several enzymes. They are used as gelling, thickening, adhesion, moisture-retention, stabilizing, film-forming, texturizing, and anti-staling ingredients.

The starch polysaccharide comprises monomers of d-glucose joined in α 1,4 linkages. Each starch granule is composed of two homo-polysaccharide fractions (amylose and amylopectin), which make up 98-99% of the dry weight of the granule. The amylose fraction of starch is an essentially linear polymer that is made up of about 99% α-(1→4) linked D-glucopyranose molecules and less than 0.5% α-(1→6) branches. The degree of polymerization of amylose ranges from 1,000-10,000 glucose units, which corresponds to a molecular weight of 105-106 . The amylose fraction makes up 20 to 30% of the starch granule while the amylopectin fraction makes up 70 to 80%. By contrast, the amylopectin fraction is a highly branched polymer consisting of about 95% α-(1→4) linked D-glucopyranose molecules and 5% α-(1→6) branches. This makes starch insoluble in cold water. Amylose and amylopectin both have an effect on the dough rheology and therefore on the structure of baked bread. Furthermore, studies report that the amylose content influences the nutritional and technological properties, such as susceptibility to enzymatic hydrolysis, and gelling and pasting behavior.

Starch determines the final properties of baked products

The choice of starch for baking depends on the specific recipe and the desired characteristics of the final product. Different starches can impart varying textures, flavors, and structures to baked goods.  Wheat starch is the most commonly used in a variety of baked products. Other starch sources such as corn, tapioca, potato, rice, and cassava have also gained popularity in the recent past, pushed by the increasing dietary restrictions among the population, especially

After gluten, starch, which makes up 70 to 85 percent of wheat flour is the second most significant part of wheat flour for bread making. The interaction of starch and gluten in dough creates a stable network that can retain fermentation gas in the dough structure and prevent the collapse of bread during baking and cooling.

When the dough is heated, starch granules absorb water, swell, gelatinize, and lose their semi-crystalline nature. The linear amylose polymers leach out of the granules leaving amylopectin-enriched granules. Starch gelatinization in the crumb causes the formation of a porous crumb structure whereas the higher temperature at the dough surface results in crust formation. Starches contribute to the flavor of baked goods and can also play a role in browning. During baking, the Maillard reaction occurs, where the combination of amino acids and reducing sugars (including those derived from starch) leads to the development of complex flavors and the characteristic brown color of bread crusts.

Starch gelatinization: The magic in baking

Gelatinization refers to the swelling and hydration of starch granules in the presence of water and heat. It is accepted that wheat starch gelatinization starts occurring between approximately 60℃ to 70℃ and a temperature of 75℃ in the oven ensures the successful gelatinization of bread.

This process is particularly important in the production of bread, pastries, and other baked products. Gelatinization during baking plays a significant role in the formation of the product structure and the changes that subsequently occur as the product is cooled and stored. However, gelatinization does not occur in all baked products, and the degree to which it occurs depends on the availability of water.

In low-moisture recipes, such as for biscuits and pastes, the water level is generally too low and the competition for that water too high for significant gelatinization to occur. In yeast-leavened dough, wheat starch dilutes the wheat gluten to an appropriate consistency, provides maltose for fermentation, and provides a surface for strong bonding with wheat gluten. During baking, it provides flexibility for loaf expansion during partial gelatinization and sets the loaf structure. When it comes to the cooling stage, it provides a rigid network to prevent the loaf from collapsing, giving structural and textural properties to the baked product.

Many factors can affect the gelatinization of starch including milling severity (particle side), grain maturity, drying techniques, water availability, and the time and temperature relationships during baking.  The relative quantities of amylose and amylopectin and their molecular arrangement have also been reported to influence gelatinization properties.

Food for yeast during fermentation

Starch also provides “food” for the yeast to feed on during fermentation. Enzymes in the yeast break down starch molecules into simpler sugars, such as glucose and maltose, through a process called saccharification. These sugars then serve as the yeast’s food, supporting its growth and fermentation activity. As yeast consumes the sugars derived from starch, it produces carbon dioxide as a byproduct. The carbon dioxide gas gets trapped in the gluten network of the dough, causing it to expand and rise. This gives the bread its light and airy texture. However, the quality of the flour used in bread making, which includes the type and amount of starch, can impact the fermentation process and the characteristics of the final bread. The fermentation time and temperature also play crucial roles in determining the flavor, texture, and overall quality of the bread.

Starch in controlling staling

Fresh bread is a product with a short shelf-life and during its storage several chemical and physical alterations occur, known as staling. As a result of these changes, bread quality deteriorates gradually as it loses its freshness and crispiness while crumb firmness and rigidity increase. Their effect on retardation of baked goods staling has been proposed to result from their interaction with starch retarding the retrogradation process, and their blocking of moisture migration between gluten and starch which prevents starch from taking up water. Retrogradation is a process that occurs in gelatinized starch as it moves from an initial amorphous state to a more ordered or crystalline state, increasing firmness. Starch retrogradation is a major factor in the staling of bread. However, attempts to slow the rate of retrogradation have initiated the development of various enzymes, emulsifiers, oligosaccharides, and polysaccharides in the food industry, particularly in the baking sector.  

Anti-staling enzyme-based ingredients help slow the onset of starch’s retrogradation. This is a natural process that occurs after baking when the two main components of starch — amylose and amylopectin — undergo a recrystallization process. “A new generation of enzymes has been discovered in some of the most amazing locations on Earth,” said Michael Gleason, senior product manager, bakery at Puratos. The company used an enzyme responsible for breaking down plant material into soft, moist elements in the development of a recently launched improver designed to make bread softer. He added that Puratos has stretched the shelf life for sweet goods in open-air display cases from 8 hours to 36 hours and added three months of shelf life to packaged snack cakes.

Kemin also markets an extensive portfolio of ingredients specific to the baking and snack industries. This includes batch packs, premixes, emulsifiers and enzyme blends for tortillas, flatbreads and baked goods. One of the enzyme blends helps prevent retrogradation by breaking down components of the dough, such as fiber, lipid, protein or starch.

“Our newly developed cultured dextrose product can be used in breads, rolls, flatbreads and tortillas,” said Art Posch, platform development manager, bakery, Kemin Food Technologies. “It can be used as a 1:1 replacement for synthetic calcium propionate in all types of yeast-raised products where a clean label, non-GMO solution is needed. It comes in both liquid and dry forms.”

In 2020, Kemin Food Technologies expanded its tortilla solutions to include not only mold inhibition but also anti-staling, TillaZyme, providing tortilla manufacturers with a label-friendly anti-staling option. 

“TillaZyme uses a mix of enzymes and gums to slow down the retrogradation process in corn tortillas, this increases shelf life in a clean label way,” said Anita Srivastava, Ph.D., CFS, senior technical service manager, bakery, Kemin.

Advancement in starch for baking

The formation of a fantastic mixture, the settling of the scrap during baking, and the real degradation of bread quality through staling are all aided by starch. However, native starch may not have the functional properties for food-processing requirements such as thickening and stabilization. Therefore, starches are often modified to overcome undesirable changes in product texture and appearance caused by retrogradation or breakdown of starch during processing and storage. Modified starches are designed to overcome one or more of the shortcomings, such as loss of viscosity and thickening power upon cooking and storage, particularly at low pH, retrogradation characteristics, and syneresis.

The catalytic reaction of a single enzyme or a mixture of more than two enzymes has been applied, generating novel starches, with chemical changes in the starch structure, in which the changes of molecular mass, branch chain length distribution, and the ratio of amylose to amylopectin may occur. These developments in enzyme technology highlight the potential to create various structured starches for the food and baking industry.

In general, the modification of starches has been traditionally conducted by physical and/or chemical methods. In contrast, recent advancement in genetic modification of starch employs transgenic technology that targets the enzymes involved in starch biosynthesis and degradation pathways in plants. In recent decades, enzymatic modifications have been adopted, partly replacing the chemical and physical methods for the preparation of modified starch, because enzymes are safer and healthier than chemical methods for both the environment and food consumers.

Recently, Cargill expanded its SimPure starches profile with a new tapioca starch that helps with structure and moisture retention due to its combination of moderate process tolerance and key functionality. SimPure 99600 improves moistness and imparts a soft texture to finished baked goods. It has a neutral flavor profile so it doesn’t have a negative impact on the finished product quality.

As we evaluate new starches, we’re careful to balance process tolerance and functional performance with other critical factors like sensory and consumer acceptance,” said Erin Radermacher, senior technical services specialist, at Cargill.

American Key Food Products (AKFP) on the other hand expanded its tapioca product line by launching native waxy tapioca starch, a gluten-free, non-GMO ingredient high in amylopectin. Sourced from AKFP’s Asian production partner, the starch has functionalities that make it an effective stabilizer, thickener and emulsifier, according to the company.

“Our native waxy tapioca starch contains a high level of amylopectin, which serves to retain water during the freeze-thaw cycle of frozen food products,” said Carter Foss, technical sales director for AKFP.

Advances in molecular and genetic engineering have also continued to offer solutions in the baking industry by altering the rations of the two major glucan macromolecules, amylose, and amylopectin. The physicochemical properties and end-uses of wheat starch are closely associated with the starch granule structure.

This feature appeared in ISSUE 7 of MILLING MIDDLE EAST & AFRICA MAGAZINE. You can read this and the entire magazine HERE