Study On The Safety And Quality Improvement Of Wheat Bran

This study collected 15 kinds of different domestic manufacturers of commercial wheat bran(coarse bran,fine bran,mixed bran)and 3 kinds of foreign wheat bran,then tested their physicochemical properties and safety index.Wheat bran of Yannong 19 was crushed and screened,getting three kinds of different particle size fractions.The basic indexes of three different particle size fractions were determined and added to flour to study the effects of different particle size fractions on dough rheological and steamed bread quality.The outermost layer of the epidermis of wheat bran are in direct contact with the outside world in circulation.So the microbial content is high,which directly affect the safety quality.Then this project studied the effect of ozone treatment on wheat bran which were from Yannong 19 and Tianjin grain group,and quantitatively analysed volatile mater of wheat bran which were treated of ozone by GC/MS.Finally,5 kinds of commercial wheat bran were treated by ozone,and studied the effects of them on dough rheological and steamed bread quality.The results are as follows:Wheat bran contains considerable amount of nutrients,including high levels of dietary fiber,crude protein,crude starch,the average contents were 44.05%,19.69%,18.64%.Due to the different raw materials and milling technology,there was a significant difference between the basic physical and chemical indicators among all samples.Among them,the crude starch,phytic acid and crude fat were the major differences,and the coefficient of variation was 27.47%,21.54%,and 19%.The results showed that total dietary fiber,ash and phytic acid content of coarse bran are higher than that of fine bran,crude fat,crude protein and crude starch content on the contrary.Analysis of safety indicators showed that the microbial content is rather high;5 samples exceed the standard of vomitoxin;2 samples exceed the standard of ochratoxin;other samples did not exceed the standard of toxins.Determination of heavy metals in only cadmium and arsenic contents respectively showed that 1 sample exceed the standard,the rest are in a limited range.Only 1 sample exceed the standard of cadmium and arsenic,and the rest are in limited range in the determination of heavy metals.Overall analysis,from the point of view of increasing dietary fiber,crude bran has more advantages;from a security point of view,fine bran more advantages.The quality characteristics of three grain size fractions showed that the epicarp,the middle layer and the aleurone layer were mainly concentrated in large size,medium size and small size range which prepared by crushed and sieved with wheat bran of Yannong 19 When the wheat bran was added to flour,dough gluten was destroyed.With the increase of the particle size,the water absorption of flour is increscent,and the mechanical properties of dough decreased,and the processing properties became worse.Steamed breads which added smaller particle bran fractions had better quality.Compared steamed buns of different fermentation methods showed that the aspect ratio,hardness,adhesiveness,chewiness of levain steamed buns are significantly less than yeast steamed bread?.The content of toxin was not been reduced during kneading dough,proofing,steaming of sour dough and steamed buns.Results showed the dry ozone treatment could make the total number of colonies in wheat bran decreased from 1.67 * 104CFU/g to 1.08 * 103CFU/g when the water cont ent was 16%,the particle size was 16 mesh,and the treatment time was 50 min of whea t ban.During the storage period the microbial content of wheat bran increased slightly,the number of volatile compounds reduced,and there were still some unpleasant smell.Bran and water(1:8)mixture were treated for 50 min by ozone,this way also can reduce 90% of the microorganisms,and the odors can be accepted by people after processing.When the bran after ozone dry treatment was added to flour,there are many small bubbles on the surface of fermenting group and steamed buns.Their surface were rough,and looked bad.When adding 20% wheat bran after dry processing to flour,this blend flour contain pungent odor,and the production process can not eliminate the smell of steamed bread.So it is unable to carry out sensory evaluation of this kind of steamed bread.The steamed bread produced by wet process has no bad smell,and the sensory evaluation is better.Dry process ozone treatment of noodles without bad odor.