Modified Wheat Starches Increase Bread Yield

Abstract

The yield of bread (amount of bread produced from a given weight of flour) is important to the commercial bread baker. Adding more water into the dough formula is an effective method of increasing bread yield with essentially no increase in processing costs. Thus, increased dough absorption is important from an economic point of view. According to the United States Food and Drug Administration Code of Federal Regulations (http://www.cfsan.fda.gov), standardized white bread produced in the United States can contain up to 38% water (USDA 2003). With most flours, it is not possible to add sufficient water in the formula to obtain bread with a final moisture content of 38%. Dough that contains excess water becomes wet and sticky and cannot be processed. In general, the amount of water lost during baking is controlled by a number of factors. These include oven temperature, baking time, surface area of the bread, and water absorption of the dough. Increased water absorption leads to higher moisture in the resulting bread and increased bread yield (Tipples and Kilborn 1968; Czuchajowska et al 1989; Puhr and D’Appolonia 1992). Dough size and shape, oven temperature, and baking time are essentially fixed in a commercial bakery. Therefore, increasing water absorption is the most practical way to increase bread yield. The water absorption of flour is determined by a number of factors including the levels of protein, arabinoxylans, and damaged starch present in the flour. Tipples and Kilborn (1968) reported that increased starch damage level and the accompanying increase in dough water absorption led to an increase in bread yield. Damaged starch imbibes water and swells at room temperature. Thus, a low level (≈5% fwb) of damaged starch has a positive effect on dough by increasing water absorption. However, at high levels (>8% fwb), the damaged starch granules interact with the gluten and change the rheological properties of the dough. The dough becomes strong but loses its elastic character. The dough is unable to expand normally during proofing and oven spring, resulting in loaves with reduced loaf volume and poor crumb grain. Added αamylase can overcome this problem by degrading the damaged starch to decrease the interaction and improve oven spring. This is the major advantage of adding α-amylase to bread flour. The degradation of the damaged starch by α-amylase also releases some of the water held by the damaged granules. Therefore, if the damaged starch level is too high, the dough becomes wet and sticky during fermentation and may produce bread with a sticky crumb. Starch can be chemically or physically modified to alter its physical properties and make it more useful in certain applications. Modifications that are commonly performed and the properties of the resulting modified starches are discussed by BeMiller (2007) and Miyazaki et al (2006). Certain of the modified starches, including pregelatinized starches, imbibe water and swell at room temperature in a manner similar to that found with damaged starch. The majority of the modified starches available are produced from corn starch. Corn starch is not compatible with gluten in breadmaking; however, wheat, rye, and barley starches are compatible with gluten (Hoseney et al 1971). Thus, modified wheat starch would be preferred in breadmaking. It is possible that certain modified wheat starches and, particularly, pregelatinized modified wheat starches might increase dough absorption in a manner similar to damaged starch but without the drawbacks described above. The modified starch may be less reactive with the gluten protein and, thus, have less effect on dough rheology. It is also possible that the modified starch would be a poorer substrate for α-amylase and not be as severely degraded during fermentation. Another approach to increasing dough absorption would be the use of the enzyme glucose oxidase which has been reported to increase dough absorption (Vemulapalli et al 1998). The objectives of this study were to determine whether bread yield could be increased by adding modified wheat starch or pregelatinized modified wheat starch to the bread formula. In addition, the effect of glucose oxidase added in combination with pregelatinized modified starch was studied.