Effect of Emulsifiers on Textural Properties of Whole Wheat Tortillas During Storage

Flour tortillas are one of the most popular and successful products in the baking industry (Hillebrand 2005). Texture and organoleptic characteristics of tortillas are major criteria that consumers use to judge the overall quality. Good quality tortillas should stay flexible and rollable without cracking and breaking when folded, and be soft without sticking together (Wang and Flores 1999). One of the major problems in tortilla quality is the deterioration of texture with time due to staling (Waniska 1999). Shelf life of tortillas can be improved through ingredients and formulation. Emulsifiers, a subset of surfactants, may impart antistaling characteristics aside from their emulsifying action (Stampfli and Nersten 1995; Seyhun et al 2003) and have been widely used by the baking industry. Sodium stearoyl lactylate (SSL), an anionic surfactant, is primarily used as a dough strengthener and a crumb softener in the baking industry. It is believed that SSL interacts with gluten during mixing, resulting in improved dough strength, and then forms a complex with amylose and amylopectin during baking. This results in crumb softening by retarding the starch staling process (DeStefanis 1977; Bernardin 1978). The strong association between SSL and gluten at the dough stage has been suggested to delay denaturation and setting of gluten during baking (Stauffer 1999). After baking, most of the SSL interacts hydrophobically with starch, which is thought to reduce the rate and extent of staling (Chung 1986). Glyceryl monostearate (GMS) is a derivative from α-monoglycerides and is known to improve texture. Similar to SSL, GMS has the ability to form complexes with amylose, hence, inhibiting the firming of baked goods due to staling (Krog and Nybu-Jensen 1970). The N-alkyl portion of GMS forms a complex with the helical regions of amylose, a phenomenon that is thought to be responsible for its effect in retarding starch crystallization, slowing the staling process. The interaction between GMS and amylose takes place at the surface of the granules, and the amylose-emulsion complex serves to stabilize the granule, retarding water penetration and swelling as the temperature is raised (Stauffer 1999). Soybean lecithin, an amphoteric surfactant, is a natural emulsifier and a mixture of phosphatides. Lecithin, unlike SSL and GMS, does not form a complex with the starch; (Stampfli and Nersten 1995). Instead, it interacts with flour gluten in baked products to extend shelf life. Lecithin is classified as a GRAS substance with a long history of safe food applications (McCormick 1986). According to dietary guidelines for Americans published by the USDA, 100 g of enriched, bleached, all-purpose white flour contains only 2.7 g of dietary fiber, whereas 100% whole wheat (WW) flour has 12.2 g of fiber/100 g of flour. Even though the importance of dietary fiber has been stressed by health organizations, including USDA, the average intake of dietary fiber of Americans is less than the recommended average by the National Cancer Institute (Hopkins Technology, LLC). Therefore, there is a noteworthy health benefit for consuming 100% WW products. Moreover, 100% WW products are rich in B and E vitamins, iron, phytochemicals, and phytoestrogens. Published research on 100% WW tortillas is scarce. Thus, the purpose of this study was to investigate the effects of three selected emulsifiers on both the objective and subjective textural properties of tortillas made from 100% WW flour.