Quality Properties Of Graded Buckwheat Flour

The nutritional value and health care value of buckwheat are generally concerned by researchers and consumers both at home and abroad.Buckwheat is rich in protein,starch,dietary fiber,mineral elements,vitamins,flavonoids and other bioactive substances.So far,there are many kinds of buckwheat flour on the market,including buckwheat flour,bran flour,different areas of buckwheat flour,buckwheat noodles,and so on.The processing level of manufacturers is different.In order to evaluate the difference between the kinds of varieties,the graded buckwheat flour of Guyang,Jingbian,Dingbian,Dingxi,Xinong9976,Xinong9978 and Canada windzar was used as experimental material.The physical and chemical properties,functional properties,antioxidant properties and the textural properties of buckwheat-wheat mixed flour dough were studied.The main conclusions are as follows:(1)The main nutrient content and physical and chemical properties of different buckwheat flour are different.The protein and ash content ranked by descending order was bran flour>whole flour>common flour>fine flour.Buckwheat starch content ranked by descending order was fine flour>whole flour>bran flour.Buckwheat bran flour had the highest water holding capacity,while the fine flour had the lowest water holding capacity.The solubility of buckwheat bran flour was significantly higher than that of whole flour,and the solubility of whole flour was significantly higher than that of fine flour.The bran flour and fine flour had a bigger expansion than the other graded flour.Water-absorbing Capacity of the graded flour ranked by decending order was bran flour>whole flour>common flour>fine flour.The oil-absorbing Capacity of whole flour was stronger than the other graded flour.There were differences between the graded flour on pasting properties.By electron microscopy,it was found that the big irregular polyhedron in the bran flour and the whole flour were more,while the spherical or smooth small particles were less.It was the opposite of fine flour and common flour.(2)Buckwheat flour contains polyphenols and flavonoids,so it has a certain antioxidant capacity.There were differences in antioxidant content and antioxidant ability between different graded buckwheat flour.The antioxidant capacity and the ability to scavenge free radicals of bran flour were stronger than whole flour,and that of whole flour were stronger than fine flour.The more the total phenolics and total flavonoids were contained,the higher the antioxidant capacity and free radical scavenging rate the flour have.(3)The composition of flavonoids and polyphenols was analyzed by high performanceliquid chromatography(HPLC).Buckwheat flour extract contained gallic acid,protocatechuic acid,p-hydroxybenzoic acid,caffeic acid,p-coumaric acid,ferulic acid,rutin,quercetin and so on.The antioxidant components and content of different varieties of buckwheat flour were different.The rutin and quercetin content was usually high which may play a major role in antioxidant capacity.Buckwheat bran flour and whole flour contained more flavonoids and polyphenols than common flour and fine flour.(4)There was an effect on the dough’s tensile properties with different proportion of buckwheat flour,fermentation temperature and time.The mixed dough added with fine flour had a greater tensile resistance than that with the addition of the whole flour,but elongation decended.There was a relatively dense gluten network structure in the microstructure of wheat flour dough,while the big and small starch granules were tightly adhered or wrapped in the membrane-like gluten.Differently,the mixed dough with 50% buckwheat had a loose and porous gluten network,and the traces of the starch particles fallen off was visible.There was no gluten structure in the dough of pure buckwheat flour and the starch granules massed.A small amount of filamentous structure was fragmented buckwheat protein.Furthermore,the fine flour of Xinong9978 was more suitable for the production of WanTuo.