Evaluation of the Effect of Sodium Stearoyl-2-lactylate Emulsifier, Xylanase Enzyme, and Alcoholic Sugar Sorbitol on the Quality of Wheat Bran Bread

 Bran-enriched bread is a source of dietary fibers and other nutritional compounds; However, wheat bran also contains phytic acid, asparagine, a high ratio of insoluble to soluble fiber, insoluble arabinoxylans, and glutathione that cause nutritional and technological problems in the product. Therefore, to produce bran-enriched bread, it is necessary to use pre-processed wheat bran. Despite the modifications made in wheat bran to improve its nutritional and functional properties, wheat bran-rich cereal products have a dark color, rough texture, and small loaf volume. To improve the quality of bran-enriched bread, common additives in the bakery industry such as enzymes, alcoholic sugars, emulsifiers can be used. Xylanase is one of the important classes of hemicellulase enzymes that delays the aggregation of amylose chains, and consequently, bread staling. Moreover, the xylanase enzyme increases the loaf volume by converting water-insoluble arabinoxylans into soluble ones. SSL emulsifier can interact with gliadin protein and prevent its participation in crosslinking bonds, which softens the bread crumbs. Polyols can reduce water activity and improve the softness of bread. Sorbitol is commonly used in starch-based foods to improve their quality by modifying starch gelatinization and retrogradation. So far, no article has been presented on the simultaneous effect of enzyme, alcoholic sugar, and emulsifier improvers on bread enriched with processed wheat bran. In addition, the amount and composition of improvers used in combination with each other can cause various effects on different properties of bread. This study aims to improve the technological, physicochemical, and finally stalling of optimal bread enriched with 15% of pre-processed wheat bran while benefiting from the nutritional properties of wheat bran.

 In this study, the effect of sodium stearoyl-2-lactylate emulsifier (0-0.8%), xylanase enzyme (0-0.05%), and sorbitol sugar alcohol (0-6%) as improving agents on The physicochemical and technological parameters of bread enriched with 15% pre-processed wheat bran were investigated based on the response surface method in the form of a rotatable central composite design. After that, design-expert software determined the optimum percentage of improvers to achieve the minimum amount of firmness and cohesiveness of bread and the maximum amount of specific volume, moisture of bread crumbs, lightness of bread crust, and solidity of bread pore structure. Finally, optimal and control samples were compared using the Differential Scanning Calorimetry and Scanning Electron Microscopic experiments.

 The experiments showed the bread's firmness under the influence of SSL emulsifier and sorbitol alcoholic sugar and chewiness, by adding SSL emulsifier and xylanase enzyme decreased significantly. All three improvers caused a significant increase in the specific volume of bread. The pore characteristics of bread crumbs, such as solidity and circularity, were significantly improved by adding an SSL emulsifier, and roundness was considerably enhanced by adding sorbitol alcohol. The brightness of bread crust was also increased significantly by the SSL emulsifier and xylanase enzyme. In addition, the Xylanase enzyme improved the moisture content of bread by substantially increasing the moisture content of bread crumbs, and alcoholic sugar and SSL emulsifier with a significant reduction in crust moisture. Moreover, the chewiness of bread on the first day after baking, specific volume, moisture of bread crust on the third day after baking, and the solidity of bread crumbs were significantly improved due to the interaction of SSL emulsifier and sorbitol alcohol. Also, the interaction of the xylanase enzyme and SSL emulsifier improved the specific volume, moisture of the bread crumbs on the first day after baking, the lightness of the bread crust,  the pore area fraction, and the circularity of the bread crumbs. Finally, the optimal formula was obtained, including 0.563% of SSL emulsifier, 0.040% of xylanase enzyme, and 2.356% of alcoholic sugar sorbitol. The results showed a significant decrease in enthalpy and an increase in the initial gelatinization temperature in the optimal sample compared to the control ones. Also, a weaker gluten network, more swelling, and amounts of starch granules in the microstructure of sample bread were observed.

 In conclusion, SSL emulsifier by interaction with amylose and amylopectin in starch granules, sorbitol alcohol via interacting with water molecules surrounding starch chains or by bonding between starch chains in amorous regions, and xylanase enzyme through reducing rate of crystallization can reduce the gelatinization of starch granules, enthalpy, and finally the retrogradation process of amylopectin and stalling rate of bread with their synergic effects. In this research, we formulate the wheat bran-enriched bread that not only benefits from the nutritional features of wheat bran but also preserves the quality characteristics of bread.