Study On The Stabilization Technology Of Wheat Bran Based On The Barrier Effect Of Aleurone Cell Walls

Wheat bran is a significant agricultural by-product in China,with an annual output of over 20 million tons.It is rich in nutritional functional components like dietary fiber,B vitamins,minerals,enzymes,and phenolic acids.As a result,it is one of the primary raw materials for processed whole wheat flour.Additionally,it serves as an essential material basis for reducing the risk of cardiovascular and cerebrovascular diseases.Despite being rich in lipids and lipase,wheat bran’s potential in food is limited due to its susceptibility to rancidity and deterioration,which affects its stability and processing characteristics.The source and distribution of lipase in wheat bran’s structural layer is not yet clear.Additionally,research is needed to determine how to limit the contact between lipase and lipids in wheat bran based on its natural structural characteristics.This would improve the quality,processing characteristics,and stability of wheat bran products.To address the issues mentioned,this project adopted hands isolation and layered debranning to obtain different wheat bran structural layers（outer pericarp,intermediate layer and aleurone layer）,analyzed the activity of lipase in different structural layers,and determined the source of lipase in wheat bran;then,using the method of centrifugal impact crushing,to obtain wheat bran aleurone cell clusters with different integrities,to study the fatty acid production rate during storage,and to clarify the influence of aleurone cell integrities on the stability of wheat bran;finally,wheat bran with different aleurone layer integrity was added back into the flour,and a comparative study was conducted to clarify its processing characteristics and storage stability in bread and noodles.This study offers new insights and theoretical technical support for stabilizing wheat bran and its added flour.（1）The wheat bran layers and their rich-fractions were obtained by hands isolation and debranning.The distribution of the wheat bran layers in different debranned fractions was determined through microscopic observation and composition determination.The lipase activity of the bran fractions was analyzed,along with the changing trend of microbial content and lipase activity during storage.It was clarified that,the exogenous lipase in wheat bran mainly came from microorganisms,while the endogenous lipase mainly came from aleurone layer.The results showed that.As the debranning rate increased,the content of ash and total phosphorus in the bran gradually increased,indicating a decrease of outer pericarp and intermediate layer,and a increase of aleurone layer;the lipase activity of wheat bran showed a trend of decreasing first and then increasing,and the lipase activity of the 6th debranning fraction was significantly higher than that of the 5th and 7th（p<0.05）;during storage,the lipase activity in wheat bran increased with the increase of the total number of colonies.The bran fraction of the 5th to 7th debranning fractions,which is rich in aleurone layer,were relatively stable;after rinsing and sterilization,the lipase activity of the bran fractions decrease significantly with the decrease of mold yeast count（p<0.05）except the 7^thfraction,indicating that the esterase or lipase in microorganisms may be the primary source of exogenous lipase in wheat bran.The lipase activity of wheat bran prepared by hands isolation and its structures showed that,the enzyme activity of outer pericarp and intermediate layer was significantly higher than that of the aleurone layer due to the influence of exogenous microorganisms（p<0.05）.However,the enzyme activity of aleurone layer was closer to that of wheat bran,and the lipase activity of hands isolation is only 1/5–1/10 of layered debranning.（2）The wheat bran fractions with different aleurone layer integrities were obtained through centrifugal impact milling.The lipase activity and free fatty acids in both bran fractions and the flour with bran during storage were studied,to determine the influence of aleurone layer cells integrity on the production of fatty acids in wheat bran and added flour,thereby storage stability.The results showed that after centrifugal impact millng and sieving,the aleurone layer in wheat bran exhibited a single-layer cell cluster structure,and its cell integrity decreased as particle size decrease;in the liquid system,oil could penetrate aleurone cell walls,and the lipase activity of wheat bran is mainly affected by the composition of the structural layers;In the powder system,as the decrease of the aleurone cell integrity,the formation rate of free fatty acid in wheat bran and its added flour also increased gradually.When the integrity was the same,the increase in water content（8–16%）would increase the hydrolysis rate of fatty acids in wheat bran and the wheat flour with them;while mold yeast count and water content show an opposite trend.Therefore,the intact aleurone layer cells can limit the hydrolysis of endogenous lipids,which is beneficial to improve the storage stability of wheat bran and its added flour.（3）The chemical composition,microstructure and functional properties of flour prepared by adding wheat bran,and commercial whole wheat flour were compared.Their processing characteristics of bread and noodles and the storage stability of products were also evaluated.The results indicated that the higher the integrity of the aleurone cells,the better the water absorption capacity and the lower dissolution rate of the wheat bran and added back flour prepared from it;The bread showed a trend of first decreasing and then increasing.During the storage process of bread,the moisture reduction rate and aging rate of the bread prepared by WF_（80-120）were slow,and the storage stability was better;the noodles prepared by WF_（80-120）are stable in color during storage,and had a relatively stable internal structure and a high water absorption rate.Its optimal cooking time is short and the cooking loss is small.Briefly,the high integrity of aleurone cells in wheat bran results in a high water absorption index of the added flour and a low water dissolution index.The prepared bread exhibits relatively good baking characteristics and storage stability,whereas the prepared noodles have good water holding capacity,gluten structure,and cooking qualities.