Physical Modification Of Red Radish Residue And Its Application In Bread

Dietary fiber has beneficial physiological functions for human body,such as preventing obesity,lowering blood glucose and regulating intestinal flora.However,the refined diet in modern life leads to insufficient dietary fiber intake,which increases the risk of“diseases of affluence”such as cardiovascular disease,hyperlipidemia and atherosclerosis.Red radish residue is a by-product of the process of extracting radish red pigment.It is rich in dietary fiber and residual pigment,and has high development and utilization value.However,the proportion of insoluble dietary fiber in red radish residue is relatively high,resulting in a rough taste.Therefore,in view of the poor edible quality of red radish residue and its limited application in food,extrusion and superfine grinding were used to modify it in this study.The changes of nutritional components,physical and chemical properties and structural characteristics of modified red radish residue were studied.The application of modified red radish residue in bread was explored and the quality of red radish residue bread was optimized by compound improver.The main results are as follows:（1）Different red radish pomace powders were obtained by superfine grinding and extrusion-superfine grinding.It was found that superfine grinding could effectively reduce the particle size of red radish residue,and the powder with particle size of D_4,3=44.97μm was obtained.Extrusion combined with superfine grinding could further reduce the particle size of red radish residue,and obtain the powder with particle size of D_4,3=35.53μm.Its specific surface area was 8.22 times that of crude powder.Compared with superfine grinding,extrusion could significantly reduce the content of insoluble dietary fiber in red radish residue,which was 9.71%less than crude powder,and the contents of free polyphenols and flavonoids were 1.13 times and 1.27 times that of crude powder,respectively.The combined modification significantly improved the water solubility of red radish residue and the water solubility index of fine powder(D_4,3=35.53μm)was 1.95 times that of crude powder.With the decrease of particle size of red radish residue,water holding capacity,swelling capacity and oil holding capacity decreased significantly but bulk density increased.Physical modification could damage the microstructure of red radish residue,changing from large blocks to debris,but without generating new chemical groups.After modification,the crystallinity and thermal stability of red radish residue increased.（2）The effects of different particle sizes of red radish residue on the properties of dough and bread were compared.The results showed that as the particle size of red radish residue decreased,the damage to dough structure decreased,but too small particle size would also affect the extensibility of dough,which was unfavorable to the specific volume of bread.When the particle size of red radish residue was 134.33μm,the bread quality was better.The effects of adding 5%,10%,15%and 20%of red radish residue on the properties of dough and bread were compared.The results showed that the larger the addition amount,the more serious the damage to dough structural and the smaller the specific volume of bread.When the maximum addition amount of red radish residue was 10%,the bread quality was still within an acceptable range.The production process of red radish residue bread was optimized by single factor experiment and the edible quality of red radish residue bread was preliminarily improved.The results showed that when the amount of water added was 65%,fermentation time was 70 min and baking time was 15 min,the quality of red radish residue bread was the best.（3）The edible quality of red radish residue bread was further improved by adding compound modifier.Under the condition of adding 0.5%guar gum,0.05%sodium stearyl lactate and 0.008%glucose oxidase,the specific volume of red radish residue bread increased by 12%,the hardness decreased by 41.25%,the sensory score increased significantly,and the comprehensive quality was close to that of wheat bread（control group）.After adding modified red radish residue,the dietary fiber content of bread increased by 161.30%,which met the standard of high dietary fiber food,and the content of free polyphenols increased by 242.47%,which improved the active function of bread.Moreover,the addition of compound modifier reduced the water loss of red radish residue bread during storage and delayed the hardening of bread.