Research On Mineral Element Analysis And Saponin Separation Method Of Quinoa

Chenopodium quinoa Willd.is native to the Andes mountain in South America,and has been introduced to China in the 1980 s,is widely planted in Qinghai,Tibet,Shanxi and other places.As influence of regional of growth,environmental factors,the quality of the quinoa is uneven,especially heavy metal pollution of quinoa has become one question of attention.Therefore,the detection of heavy metals is very important to evaluate the quality of quinoa,monitor the environment of producing area and exploit of quinoa.The "de-husk and de-soapen" of quinoa is beneficial to the consumption of quinoa and development of products.Therefore,there are 21 kinds of quinoa from different producing areas and varieties were selected,The determination of heavy metals and mineral elements in quinoa was studied.Single factor and response surface tests were used to determine the optimal conditions for super microwave digestion.Quinoa saponins were isolated by foam separation technique,the effects of air velocity,dilution ratio,liquid volume and temperature on the foam separation of quinoa saponin were investigated.The main conclusions are as follows:(1)Microwave digestion and super microwave digestion are compared and studied.To determine the optimal conditions for super microwave digestion.The response surface optimization model was established with digestion power,nitric acid concentration,nitric acid volume and digestion temperature as independent variables and digestion efficiency as dependent variable.It was found that the factors affecting the digestion rate were digestion time,digestion temperature,digestion power and nitric acid volume.The optimal digestion conditions of quinoa were as follows: digestion time 26 min,digestion power 1200 W,digestion temperature 240℃ and nitric acid volume 4 mL.(2)Determination of heavy metal contaminants and mineral elements in quinoa samples from different producing areas by the optimized conditions of super microwave digestion.Almost no heavy metal pollutants As,Pb and Hg were detected out in quinoa from different producing areas.Cd could be detected out in quinoa samples from Hebei,Shanxi,Inner Mongolia and Yunnan,Cr could be detected in quinoa samples from Qinghai,imported,Hebei and Shanxi,but the results all met the national standards.The contents of K and Mg in quinoa samples from all regions were significantly higher.The contents of Fe、Mg、Ca and K were all high in the samples from North China,and the Zn content was significantly lower than that from other regions.The Contents of Mn and Zn in the samples from Southwest China were significantly higher than that from other regions,the Fe content was significantly lower than that from other regions,and the K content in the imported samples was significantly lower than that from domestic samples.(3)Quinoa saponins and four heavy metal pollutants by wet process was better than that by dry process,and the mixed process was the best.The advantages of mixed process are obvious.The clearance rate of Cd was the lowest,and the clearance rate of mixed method was obviously higher.Pb is the easiest to remove.The preservation rate of Mn and Cu is the lowest in the mixed process,which has some advantages compared with the dry and wet methods.The preservation rate of Zn and Fe by mixed method is higher than that by wet method,but the preservation rate of Mn,K,Ca,Na and Mg is the lowest.Considering the removal rate of saponins and four heavy metals,although the loss of some mineral elements after mixed process is slightly higher,it still has certain advantages.(4)Using foam separation technology to separate quinoa saponins from quinoa bran powder,the effects of Airflow velocity,dilution ratio,liquid volume,temperature and other factors on the foam separation effect of quinoa saponins were studied.The results showed that the higher the dilution ratio,the higher the temperature,the smaller the gas flow rate,the higher the saponin enrichment ratio.The recovery rate of saponins changes greatly with the change of dilution ratio,temperature,gas flow rate and liquid volume.The smaller the dilution ratio,the lower the temperature,the larger the gas flow rate and the larger the liquid volume,the higher the recovery rate of saponins.Through single factor test and response surface analysis,the optimal conditions for the separation of saponins from quinoa peel powder were as follows: dilution ratio 50,temperature 25℃,gas flow 22 mL/min,liquid volume 250 mL.Under these conditions,the enrichment ratio was 2.53,and the recovery rate was 46.08%.The results showed that the optimized conditions were practical and the utilization efficiency and value of quinoa bran powder were improved.