Investigating dough rheology and texture properties of bakery products containing soy or pulse flours

Abstract

Soybean and pulse flours are excellent source of various macro- and micro-nutrients, such as proteins, dietary fibers, minerals, and bioactive compounds associated with health benefits. They are becoming increasingly important to the food industry as product formulators and consumers are seeking nutritionally attractive ingredients. Fortification of cereal foods with pulse or soybean flour represents a promising approach to enhance their nutritional value, health benefits, and flavor profiles. However, the lack of gluten protein in these flours results in undesirable dough rheological properties and baked products with poor texture and other quality defects. This thesis is comprised of two studies that aimed to investigate and understand the effect of incorporating soybean or pulse flours on the dough properties and bakery product quality. In the first study, we investigated the effect of formulation (e.g., shortening, sugar, and water) and pretreatment of soy flour on dough properties and cookie texture in a gluten-free (GF) system. Cookies were formulated with composite flours containing commercial GF flour and original or pretreated soy flour (70/30). Reducing agents (cysteine, glutathione, and sodium sulfite) and protease (Flavourzyme) were used for soy flour pretreatment, respectively. The modified proteins were characterized by analyzing contents of free sulfhydryl and free amino group and SDS-PAGE profiles. Dough properties were measured using mixograph and texture analyzer. Cookie quality was determined by analyzing spread ratio, texture, color, and moisture content. Results showed that adding relatively higher amount of sugar, shortening, and water greatly increased cookie spread and improved cookie cracking pattern, though it also increased the stickiness of the dough. Pretreatment of soy flour with reducing agent or protease reduced protein molecular size, and thus, weakened the GF dough, which also led to increased cookie spread and better cracking pattern. In the second study, we investigated the effect of different types (yellow pea, green pea, red lentil, and chickpea) and amounts (0-25%) of whole pulse flours on whole wheat flour-based dough properties and bread quality. Pulse grains were ground using a Wiley mill to obtain whole pulse flour. Mixolab was used to analyze mixing and pasting properties of the whole wheat/pulse composite flours, and bread was characterized. Results showed that increasing the amount of pulse flour in the composite significantly weakened the dough and decreased dough viscosity due to a dilution of gluten proteins. Bread specific volume decreased, and hardness increased with higher amount of pulse flours. Among all the tested pulse flours, the composite flour containing yellow pea flour had overall better baking performances. This research demonstrated the potential of utilizing soybean and pulse flours for bakery applications. The knowledge will be useful for the industry in developing new gluten-free or fortified bakery products.