The effect of moist and dry heating in different particle sizes of wheat flour on the quality characteristics of bread

Introduction: Wheat is a staple food for most people in the world but it cannot be used without processing. The nutritional importance of wheat flour is due to the presence of gluten proteins that create viscoelastic properties (Sudha et al., 2016). Gluten is the most important factor in volume and texture uniformity, efficiency and water absorption, aroma, and flavor in wheat flour products. One of the most useful components of flour is the collection of gliadin and glutenin proteins, which form gluten after mixing with water. The gluten network is the main determinant of the important characteristics of the dough, including extensibility and resistance to stretching, tolerance to mixing and the ability to hold gas, which encloses starch granules and fibrous parts (Payan, 1393). Weak wheats have less protein and the flour, dough and bread produced from them are not of good quality. To solve this deficiency, chemical modifiers or improvers and physical modification of flour are used (shanmugavel et al., 2019). Physical modification of flour is a safe method without using any kind of chemicals. physical modification of flour includes heat treatment and particle size classification (Rosa zavareze et al., 2011). Particle size distribution is the most widely used technique for classifying solid particles, which is effective in improving rheological properties by affecting the physicochemical properties of flour during hydration, such as water absorption, solvent retention, sedimentation, and adhesion properties (Pang et al., 2021). Heat treatments, depending on the intensity of temperature and process time, by modifying starch granules, denaturing proteins, deactivating enzymes, reducing microbial load, and even modifying flavor and aroma are suggested as a suitable way to improve the quality of bread, especially for weak flour (Chakraborty et al., 2022). Considering that the interaction of particle size with moist and dry heating of wheat flour on the qualitative characteristics of bread has not been studied so far, in this research, by dividing wheat flour with different particle sizes and using moist and dry heat treatment for modification the functional characteristics of wheat flour and the improvement of the qualitative characteristics of bread were investigated. Material and methods: The content of moisture, pH, ash, protein, and zelny of wheat flour was measured using AACC standard method (2000), and wet and dry gluten with standard numbers (9639-1,3) was measured. To classify the size of the particles, wheat flour was divided by a shaker sieve with different sizes of 180, 150, and 125 microns, then under the influence of dry heat treatment for 10 minutes at 100 degrees Celsius and moist heat treatment with humidity, 16% for 5 minutes at a temperature of 96 degrees Celsius was placed. To produce gluten with bread, the formulation used by Farhen in 2012 was used with a slight change. materials for gluten with bread formulation for 100 grams of wheat flour included 58 ml of water, 2.5 grams of sugar, 1 gram of salt, 1 gram of vegetable oil, and 2 grams of yeast. Bread tests, which include weight loss, specific volume, oven spring, Crumb to crust ratio and shape indexes, were studied to evaluate the quality of bread. Shape indexes include volume index and uniformity index and symmetry index. To check the staleness of bread during the storage period test DSC was used. Finally, the factorial test was used to investigate the effects of particle size and heat treatment of wheat flour, and Duncan's multiple range test was used to compare the means at the 5% probability level. Results and Discussion: The results showed that the effect of thermal treatments on uniformity and symmetry index and weight loss was not significant (p>0.05). The effect of particle size on the uniformity index was not significant (p>0.05). Moist heat treatment and particle size of 125 microns led to an increase in specific volume, volume index, oven spring, and ratio of crumb to bread crust (p<0.05). Thermal analysis of bread showed that the sample of bread obtained from moist heat treatment during the storage period had the lowest amount of retrogradation enthalpy and led to the improvement of bread quality and staleness (p<0.05). Conclusion: The results of the research showed that the use of moist heat treatment and the particle size of 125 microns improved the quality of bread, so that the moist heat treatment causes the dough to expand by keeping gas and air in the dough and causes the starch gelatinization temperature to increase and the delayed gelatinization to prolong the expansion period and further development of the dough during baking, this caused an increase in the volume and specific volume of the spring bread. The lower retrogradation enthalpy of the moist heat treatment sample led to improved bread quality and staleness. In general, the use of flour with a particle size of 125 microns and moist heat treatment were the best examples for improving the quality of bread.
ntroduction: Wheat is a staple food for most people in the world but it cannot be used without processing. The nutritional importance of wheat flour is due to the presence of gluten proteins that create viscoelastic properties (Sudha et al., 2016). Gluten is the most important factor in volume and texture uniformity, efficiency and water absorption, aroma, and flavor in wheat flour products. One of the most useful components of flour is the collection of gliadin and glutenin proteins, which form gluten after mixing with water. The gluten network is the main determinant of the important characteristics of the dough, including extensibility and resistance to stretching, tolerance to mixing and the ability to hold gas, which encloses starch granules and fibrous parts (Payan, 1393). Weak wheats have less protein and the flour, dough and bread produced from them are not of good quality. To solve this deficiency, chemical modifiers or improvers and physical modification of flour are used (shanmugavel et al., 2019). Physical modification of flour is a safe method without using any kind of chemicals. physical modification of flour includes heat treatment and particle size classification (Rosa zavareze et al., 2011). Particle size distribution is the most widely used technique for classifying solid particles, which is effective in improving rheological properties by affecting the physicochemical properties of flour during hydration, such as water absorption, solvent retention, sedimentation, and adhesion properties (Pang et al., 2021). Heat treatments, depending on the intensity of temperature and process time, by modifying starch granules, denaturing proteins, deactivating enzymes, reducing microbial load, and even modifying flavor and aroma are suggested as a suitable way to improve the quality of bread, especially for weak flour (Chakraborty et al., 2022). Considering that the interaction of particle size with moist and dry heating of wheat flour on the qualitative characteristics of bread has not been studied so far, in this research, by dividing wheat flour with different particle sizes and using moist and dry heat treatment for modification the functional characteristics of wheat flour and the improvement of the qualitative characteristics of bread were investigated. Material and methods: The content of moisture, pH, ash, protein, and zelny of wheat flour was measured using AACC standard method (2000), and wet and dry gluten with standard numbers (9639-1,3) was measured. To classify the size of the particles, wheat flour was divided by a shaker sieve with different sizes of 180, 150, and 125 microns, then under the influence of dry heat treatment for 10 minutes at 100 degrees Celsius and moist heat treatment with humidity, 16% for 5 minutes at a temperature of 96 degrees Celsius was placed. To produce gluten with bread, the formulation used by Farhen in 2012 was used with a slight change. materials for gluten with bread formulation for 100 grams of wheat flour included 58 ml of water, 2.5 grams of sugar, 1 gram of salt, 1 gram of vegetable oil, and 2 grams of yeast. Bread tests, which include weight loss, specific volume, oven spring, Crumb to crust ratio and shape indexes, were studied to evaluate the quality of bread. Shape indexes include volume index and uniformity index and symmetry index. To check the staleness of bread during the storage period test DSC was used. Finally, the factorial test was used to investigate the effects of particle size and heat treatment of wheat flour, and Duncan's multiple range test was used to compare the means at the 5% probability level. Results and Discussion: The results showed that the effect of thermal treatments on uniformity and symmetry index and weight loss was not significant (p>0.05). The effect of particle size on the uniformity index was not significant (p>0.05). Moist heat treatment and particle size of 125 microns led to an increase in specific volume, volume index, oven spring, and ratio of crumb to bread crust (p<0.05). Thermal analysis of bread showed that the sample of bread obtained from moist heat treatment during the storage period had the lowest amount of retrogradation enthalpy and led to the improvement of bread quality and staleness (p<0.05). Conclusion: The results of the research showed that the use of moist heat treatment and the particle size of 125 microns improved the quality of bread, so that the moist heat treatment causes the dough to expand by keeping gas and air in the dough and causes the starch gelatinization temperature to increase and the delayed gelatinization to prolong the expansion period and further development of the dough during baking, this caused an increase in the volume and specific volume of the spring bread. The lower retrogradation enthalpy of the moist heat treatment sample led to improved bread quality and staleness. In general, the use of flour with a particle size of 125 microns and moist heat treatment were the best examples for improving the quality of bread.