Study On Physicochemical Properties Of Different Wheat Flour And The Influence On Browning Of Wheat-based Products

Browning is an important factor impacting the industrial production of wheat-based products.In this research,wheat flour was prepared from 61 wheat cultivars which planted widely in China.The fresh dough sheets and fermented dough were prepare using these wheat flours to investigate the effects of physicochemical properties(e.g.protein content,wet gluten content,polyphenol content,and polyphenol oxidase activity)on browning of flour products.The key components influencing qualities of the steamed bread were also detemined by means of TPA test and sensory evaluation.For the production of traditional flour products,we can make use of it for reference.The main results were as follows:(1)The physicochemical properties such as protein content,wet gluten content,polyphenol content and polyphenol oxidase activity(PPO)of 61 wheat flours were determined.Results showed that the number of the strong gluten wheat flours,medium-strong gluten wheat flours,and medium gluten wheat flours were 28?24?and 9 respectively.The distribution of PPO was concentrated on122~320 U·g-1· min-1,and the average value of polyphenol oxidase activity was 222 U·g-1· min-1.The percentage of wheat varieties with PPO of 150 ~ 270 U·g-1· min-1 was 80.33 %.The polyphenol contents of the 61 wheat flours were also determined.The result indicated that the distribution of polyphenol content was 9.63~25.15 mg/g,and the average value of polyphenol content was 17.07mg/g.The number of varieties with polyphenol content of 11~21 mg/g was 80.33 %.Moerover,wet gluten content was positively correlated with protein content(P < 0.05),and negatively correlated with PPO activity(P < 0.01).Polyphenol content was positively correlated with PPO activity(P < 0.05).(2)The effects of physicochemical properties on the browning of fresh dough sheets which made from 61 wheat flours were studied.Results showed that fresh dough sheets browned quickly in0~4 h,and then the browning become slowly.PPO activity was negatively correlated with L*,?a*,and positively correlated with ?L*0~ 2 h,?L*0~ 4 h,?L*4~ 24 h,?L*0~ 24 h,a*(P < 0.01).Polyphenol content was negatively correlated with L*0 h,L*0.5 h,L*1 h,L*2 h,L*4 h(P < 0.05),?a*,?b*0~ 24 h(P < 0.05),and positively correlated with a*(P < 0.01),b*24 h(P < 0.05).Protein content was negatively correlated with L*0 h(P < 0.01),L*0.5 h,L*1 h,L*2 h,?b*0~1 h(P < 0.05).Wet gluten content was negatively correlated with a*0 h,a*0.5 h,a*1 h,a*2 h,a*4 h,a*24 h(P < 0.05),and positively correlated with ?a*0~0.5 h,?a*0~4 h(P < 0.05),?a*0~1 h,?a*0~2 h(P < 0.01).In conclusion,L* was influenced by PPO activity,polyphenol content and protein content during 0 h to 2 h.Between 2 h~4 h,L* was mainly affected by PPO activity and polyphenol content.After 24 h storage,The change of L* only depends on PPO activity.The color of fresh dough sheets were correlated with PPO activity,polyphenol content and protein content.The wheat flour with higher PPO activity,polyphenol content and protein content would result in the lower L* for initial fresh dough sheets.Moreover,the fresh dough sheets made from the wheat flours with higher PPO activity would have higher browning rate.(3)The effects of physicochemical properties on the browning of fermented dough made with wheat flour were studied.Results showed that Protein content was negatively correlated with L*0 h(P< 0.05),L*4 h(P < 0.01),and positively correlated with?L*0~ 4 h,?*a0~0.5 h(P < 0.05).PPO activity was negatively correlated with L*0 h,L*2 h,L*4 h(P < 0.01),L*0.5 h,L*1 h(P < 0.05),and positively correlated with ?L*0~4 h(P < 0.01).Polyphenol content was positively correlated with a*2 h(P < 0.05).There was no significant correlation between wet gluten content and the browning rate within 4 h.In conclusion,the main factors effecting browning of fermented dough were protein content and PPO activity.(4)The effects of physicochemical properties on the quality of steamed bread were studied by means of TPA test and sensory evaluation.The results indicated that protein content was positively correlated with specific volume,adhensiveness,springness,cohesiveness,resilience(P < 0.01),and negatively correlated with hardness,gumminess,structure,appearance,tenacity,viscosity,total score(P < 0.01).Thus,high protein content is beneficial to increase the specific volume,reduce the hardness,fastly recovery in the process of pressure the steamed bread.However,high protein content was not favorable for good appearance,internal structure and tenacity.Moreover,high protein content reduced the total score of the steamed bread.wet gluten content was positively correlated with specific volume,springness,cohesiveness,resilience(P < 0.05),and negatively correlated with viscosity(P < 0.05).