Nonthermal Dehulling Technology And Equipment For Tartary Buckwheat

Tartary buckwheat is a kind of medicine and food dual-purpose traditional crops.Because the enormous health benefits of tartary buckwheat products,it is favored by more and more consumers.Since the shell and kernel of tartary buckwheat is clingy and brittle,the whole kernel rate is very low after the dehulling process,it has already restricted the development of tartary buckwheat deep processing.At the present stage,the ripening dehulling technology improved the the whole kernel rate of tartary buckwheat dehulling at a certain extent,but the specific active nutrients of tartary buckwheat was reduced more than 75%.Therefore,developing a tartary buckwheat nonthermal dehulling machine,with high whole kernel rate,is significant for the development of tartary buckwheat processing industry.Through test on the dehulling characteristics of tartary buckwheat and combining with the research of tartary buckwheat dehulling technology at home and abroad,this thesis designed a tartary buckwheat nonthermal dehulling machine with the "rubbing" and "kneading" working process.The main tasks and results of this paper are as follows:(1)The relevant dehulling characteristics of tartary buckwheat were studied by experiments based on “Chuanqiao No.4”.Firstly,through measuring the physical parameters of the test sample,the 1000-grain weight was 19.4g,the bulk density was 668 g,the moisture content was 12.14%.Secondly,the critical damage pressure value of the test sample reached the maximum value 85 N which the water content of test sample were 15%~20%,and the compression resistance capability on the long axis of test sample was better than the short axis.Thirdly,the diameter of test sample in the range 2.7~3.0mm was the highest proportion at 54.35%.Fourthly,this thesis determined the weakest part of the Tartary buckwheat shell which was located at the physical ridges through observing the microstructure of the test sample.Finally,according to the shell structure characteristic of tartary buckwheat,this thesis proposed a way of tartary buckwheat nonthermal dehulling,combined with the “rubbing” and “kneading” process through the preliminary experiments,it verified the feasibility of this dehulling way.(2)The tartary buckwheat nonthermal dehulling machine consisted of feeding device,rubbing device,kneading device,discharging device and a power transmission device.The main working process included two stages which were rubbing and kneading,the stage of rubbing grind off the ridges of the tartary buckwheat shell,the stage of kneading made the shell and kernel striped.The rubbing pressure,rubbing regional gap,kneading pressure,kneading regional gap and working rotation speed of the machine could be controlled by requirements.(3)This thesis carried out the single factor dehulling experiments based on the designed machine,and obtained the optimal factor level value.The rubbing regional gap was 3~4mm,the rubbing pressure was 15~22.5kPa,the kneading regional gap was 5~6.5mm,the kneading pressure was 10~15kPa,the rubbing roller speed was 450~550rpm.(4)This thesis designed orthogonal rotation combination experiments based the optimal factor level value range from single factor experiments.Through analysing the experimental data,it sought and tested the optimal prediction value of whole kernel rate and hulling rate,it obtained the optimal value of those factors.While the rubbing regional gap was 2.6mm,the rubbing pressure was 22.3kPa,the kneading regional gap was 4mm,the kneading pressure was 5.1kPa,the rubbing roller speed was 470 rpm.The whole kernel rate and dehulling rate achieved the maximum about 31.84% and 88.11% respectively.