| Naked oat is the main cultivated oat variety in China,it is gradually accepted by consumers due to its unique nutritional characteristics,while the influence mechanism of stir-frying on its quality is unclear.And naked oat after stir-frying was milled directly without peeling during the traditional processing.In this paper,naked oat was peeled by two kinds of peeling machines to study the changes of quality and total number of colonies of peeled oat and oat rice,on this basis,the peeled naked oat after stir-frying was investigated to explore the effect of different degrees of stir-frying on oat starch,oat protein and oat lipid.Finally,naked oat after stir-frying was milled to study the effect of stir-frying on milling and oats flour quality combing the changes of the key components.The results were shown as follows:Naked oat was peeled by the traditional peeling machine and the peeling machine with flexible alloy blade to study the effect of different peeling machines on oat peeling rate,broken rate,microstructure,microbial content and activity of lipase.It was found that peeling rate of the peeling machine with flexible alloy blade was higher than the traditional peeling machine,and the broken rate was lower.The flexible peeling process was more precise and uniform,without damaging the aleurone layer and endosperm from SEM.To compare with the unpeeled oat,a 30 s peeling treatment reduced the microbial content of oat grain surface and reduced the activity of lipase effectively.The optimal peeling parameters by the peeling machine with flexible alloy blade: peeling time 30 s,tempering time 14 h,second-addition of water 2%,and second-tempering time 5 min.The effect of stir-frying on pasting characteristics,solubility and swelling power,particle size distribution,crystal structure and microstructure of naked oat starch was studied.After stir-frying for 0-40 min,the gelatinization degree of oat starch gradually increased(19.8%,31.2%,46.5%,68.7% and 77.2%).The RVA results showed the peak viscosity decreased from 4457 cP to 1911 cP after a 30 min stir-frying,the change of pasting temperature was not significant.The solubility of oat starch increased first and then decreased,the swelling power increased.The median particle size diameter,volume mean diameter and length mean diameter of oat starch increased significantly,while the specific surface area decreased significantly.The results of X-ray diffraction(XRD)showed that the crystal type of starch did not change.The structure of starch was destroyed and aggregation occurred by SEM.The effect of stir-frying on oat protein was explored by secondary structure,content of sulfhydryl group,surface hydrophobicity,water binding capacity and oil binding capacity.It was found the content of ?-sheet of oat protein after stir-frying decreased from 35.96% to 29.51%,the ?-turn content increased from 3.11% to 34.78%,and the a-helix content increased from 16.84% to 20.78%.The content of sulfhydryl group increased with the maximum value of 18.33 ?mol/g.The surface hydrophobicity of the protein gradually decreased with the minimum value of 200.97.Oil binding capacity decreased to 1.75 g/g,and water binding capacity increased to 1.58 g/g.The effect of stir-frying on oat lipid was measured through extraction rate of lipid,fatty acid value,peroxide value,main fatty acid composition and distribution.The results showed that the extraction rate of lipid increased to the maximum value of 8.61% after a 30 min stir-frying.The fatty acid value increased from 0.87 mg/g to 1.33 mg/g and peroxide value increased from 0.05 g/100 g to 0.42 g/100 g after stir-frying.While the main fatty acid composition did not change much.The images of laser confocal scanning microscopy showed that the degree of lipid exposure in the treated oat grains increased and the distribution was more uniform.The effect of stir-frying on oat flour yield and quality was studied after milling.The results showed compared with oat without stir-frying,the oat flour yield(52.96%)increased by 15.31%.The median particle size diameter and volume mean diameter of the oat flour increased significantly,while the specific surface area and length mean diameter decreased.The angle of repose decreased from 49.23° to 44.71°.The RVA results showed the peak viscosity,breakdown values,setback values and final viscosity of oat flour decreased significantly after stir-frying.Its elastic modulus was higher than that of untreated oat flour during temperature scanning.During frequency scanning,it was found that stir-frying could reduce the damping factor of oat flour and make oat flour paste turn to elastic solid. |
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