Study On Characteristics Changing Of Wheat Flour Quality During Maturing Process

In order to study on the characteristics change of wheat flour quality during maturing process and the difference of maturing properties between the head and tail flour stream, physiologically matured wheat grain was used as the raw material. The physical-chemical properties of the new grinding wheat flour after different storage period(0, 10, 20, 30, 40, 50, 60, 70, 80, 90 d) were analysized to determine the optimized maturation time of flour. The quality of flour from different varieties of wheat in the optimized maturation time was then compared. Finally, this article also studied the effect of maturing treatments other than storage on the flour quality. The analyzed results were shown as follows:The followings were the basic quality changes of flour during maturing process. With the increase of maturation time, flour moisture, crude protein, sedimentation value, solvent retention, color grade value and yellowness value decreased. Damaged starch content, falling number, gluten index, whiteness and brightness value increased. Gluten content and swelling index of glutenin firstly increased and then decreased. The quality parameters of flour during maturing process did not increased or reduced linearly, significant peak or trough appeared between 30~60 d. Falling number, gluten index and brightness were positively correlated with maturation time. The changes during maturing process for the basic quality indicator of the head tail flour were simillar, the head flour had color and gluten strenth than the tail flour.Changes in rheological properties of flour during maturing process were shown. With the increase of maturation time, the water absorption of dough firstly increased and then decreased, with the lowest was at about 50 d. Development time, stability time and farinograph quality number increased significantly, with the largest was at about 40~50 d. Softening firstly decreased and then increased, with the lowest was at about 40~50 d. Paste viscosity, breakdown values firstly decreased and then increased, with the largest was at about 40 d. Setback value increased during maturation process. The development time, stability time, farinograph quality number, paste viscosity, breakdown values and setback value were significantly positively correlated with maturation time, softening of dough was significantly negatively correlated with maturation time. The water absorption and softening of tail flour were higher than that of head flour. Pasting viscosity of head flour was higher than tail flour.Changes in flour product quality during maturing process were shown as followings. Steamed bread made from flour matured for 40~50 d had the best quality, maturation time had little effect on noodle quality, while significantly influenced the yellowness value of dough sheet. Influences of maturation time on steamed bread quality were significant. There was significant difference among index with varying time. The tail flour had poor quality due to their high bran content, while the head flour had better quality. The quality of flour stored for 40~50 d was the best, comprehensively consideration, the optimized maturation time of flour was 40 d. The most significant change during maturing process were rheological properties, color and gluten characteristics.Changes of quality for flour from different varieties of wheat were shown. The water-soluble content, color grade value, yellowness value, degree of softening, springiness, cohesiveness, resilience and loss factor for flour in optimized maturation time were less than that of new grinding wheat flour; while whiteness, brightness, gluten content, gluten index were higher than the former. Optimized maturation period would improved flour quality, the difference among wheat varieties were reflected in the different magnitude of change, the color grade value of soft wheat decreased by as much as 50%, the growing degree of pasting properties for medium hardness wheat was 10%, the declining degree of weakening of durum wheat was 25%, the growth degree of the hardness for the products reached more than 20%.Maturing treatments could accelerate the maturing process. The quality of flour was significantly improved by adding 20 ppm azodicarbonamide, 20 ppm glucose oxidase and 37? for 1 h heat treatment, with resistance dough fermentation improved by 36%, gas holding capacity improved by 1.5% and dough viscoelasticity improved significantly. Starch and protein binding of matured flour was denser compared with new grinding wheat flour. The natural maturation time could be shortened by maturing treatment and thus the quality of flour was significantly improved.