Saturated Hot Air Peeling Process Optimization And Its Effect On The Physical And Chemical Indexes Of Bitter Almonds And Peels

The peeling is an important procedure in the first step of apricot kernels processing.At present,the traditional blanching method(blanching in boiling water of about 95 to 100℃ for 5 to 10 minutes)and alkali treatment method were widely used in apricot processing industry.These peeling methods will lead to the loss of functional components such as polyphenols and flavonoids in the skin of apricot kernels through peeling water.In addition,the content of organic in the peeling water exceeds the standard,which will cause serious environment pollute and waste of resources if is directly discharged.Therefore,in view of the resource and energy waste in the traditional peeling process of apricot kernels,this study proposes to use the saturated hot air conditions created by the steam oven to achieve green peeling.Firstly,the response surface optimization design test were used to determine the best conditions of removing apricot kernels skin by saturated hot air method.Meanwhile,the effects of different treatment temperature and treatment time on physicochemical indicators of apricot kernels and skin were studied.The results of this study are as follows:1.In the process of apricot kernels peeling,the temperature and humidity changes in the steam oven were monitored in real time by temperature acquisition device and temperature and humidity indicator.The results showed that the relative humidity in the steam oven reached 99.9%after 2 minutes of lag,which proved that the air state in the steam oven was saturated hot air.Based on this,the optimum parameters for saturated hot air method removing apricot kernels skin by the response surface optimization design test were:treatment temperature 65℃,treatment time 6 min,immersion time 23 min and the liquid ratio was 1:2.Under the optimum saturated hot air peeling condition,the peeling rate of apricot kernels is as high as 99.33%,and the relative error between the prediction and the quadratic model is 0.67%.It shows that the predicted value is in good agreement with the measured value,and the model can simulate the actual situation well.2.The effects of different treatment temperature and treatment time on the physicochemical indicators of apricot kernels were studied,the results showed that compared with the traditional boiling water method,the saturated hot air method can greatly retain the content of amygdalin,the activity of beta-glucosidase was significantly affected by treatment temperature and treatment time,and the loss of protein and reducing sugar decreased,and the loss of apricot kernels oil did not different much.The heatmap analysis of various indicators in apricot kernels after different treatments revealed the content of each physicochemical index is highest in original sample,the treatment temperature too high and the treatment time too long,which will cause the decrease of beta-glucosidase activity,protein and reducing sugar but not affect the content of amygdalin and apricot kernels oil.3.The effects of different treatment temperature and treatment time on the physicochemical indicators of apricot kernels skin were studied.The heatmap analysis of various indicators in apricot kernels skin after different treatment revealed the content of total phenol,total flavonoids and monomeric phenol in the apricot kernels skin was lowest by the traditional boiling water method treated and the content of total phenol,total flavonoids and monomeric phenol in apricot kernels skin decreased with the improve of treatment time.The correlation between physicochemical indicators and color values of apricot kernels skin showed that total phenolics,total flavonoids and catechins in apricot kernels skin were significant and positively related to b*and C*.Compared with the traditional peeling method,the saturated hot air method greatly reduced the loss of polyphenols and flavonoids in the apricot kernels skin.The loss rate of total phenol decreased by 42.3%,the loss rate of total flavonoids decreased by 50.5%,and the loss rate of four monomeric phenols(protocatechuic aldehyde,catechin,vanillic acid,chlorogenic acid)decreased by 57.8%,63.3%,94.5%,42.5%respectively.