Physicochemical Properties Of Buckwheat Flour And Quality Of Buckwheat Instant Noodles Treated By Differential Pressure Type Puffing Technology

Buckwheat,as a kind of food with high nutritional value,has high health care function,and obtains deeply loved by the masses.Buckwheat doesn't contain gluten.This characteristic makes it difficult to develop and utilize.The healthy and delicious buckwheat processed food is rare in market.In this paper,buckwheat was taken as the research object.The problem that it is difficult to form dough only by buckwheat flour as raw material to make noodles was solved by using differential pressure type puffing(DPTP)technology and twin-screw extrusion technology.Pressure difference pre-treatment of buckwheat granules was studied from three factors:process time,drying temperature and puffing pressure.Taking gelatinization degree as an index,a relatively great treatment condition of process time of 10 min,drying temperature of 70?,puffing pressure of 0.20 MPa was deter mined.Then the effects of pre-gelatinization on the physicochemical properties of buckwheat flour were analyzed from the microstructure,crystal structure and pasting properties.The following results were obtained:(1)The pictures of scanning electron microscope(SEM)and X-ray diffraction(XRD)showed that the DPTP treatment destroyed the buckwheat starch granules to a certain extent and decreased the crystallinity.(2)Differential scanning calorimetry(DSC)analysis showed that the ?H of buckwheat flour decreased from 266.79 J/g to 249.55 J/g,the conclusion temperature decreased from 125.44? to 110.02?,and the peak temperature increased from 82.83?to 93.36?.(3)RVA results showed that the peak viscosity and final viscosity increased significantly with DPTP treatment,especially the peak viscosity increased from 1169 Pa.s to 2181 Pa.s,and the breakdown viscosity decreased from 330 Pa.s to 127 Pa.s.The extrusion process of buckwheat instant noodles was studied by the three influencing conditions of material moisture,outlet temperature and screw speed.The optimum extrusion process was deter mined by tensile and texture analysis,cooking loss and sensory evaluation.The conditions are moisture of 37%,temperature of 115? and screw speed of 72 r/min.In addition,the effects of DPTP treatment on the quality and properties of buckwheat noodles were analyzed.(1)The texture of the product was determined to be 110.29 g in hardness,1.00 g in elasticity,0.69 g in cohesiveness,29.04 g in chewiness,0.57 in recoverability,76.69 g in tensile force and 16.57 cm in tensile distance.The rate of cooking broken is 6.28%,and the rate of cooking loss is 16.31%.(2)After ripening,the viscosity and elasticity of the product were increased,and the content of flavonoids were decreased from 17.6 mg/g to 20.3 mg/g.The content of RDS,SDS and RS were 15.6%,21.6%,and the 62.8%respectively.The data showed that the in vitro digestibility of buckwheat flour with DPTP treatment decreased.(3)In addition,the microstructure of the extruded buckwheat instant noodles was observed by SEM.It was found that the pre-treatment destroyed the starch.XRD and fourier infrared spectrometer(FT-IR)showed that DPTP treatment destroyed the crystal structure of the starch and decreased the crystallinity.DSC and Low-field nuclear magnetic resonance(LF-NMR)indicated that pre-treatment made the free water in buckwheat flour transferred to the strong adsorbed water and weak adsorbed water.