Study On The Changes Of Amygdalin And β-glucosidase During The Process Of Ultrasonically Induced Debittering Of Bitter Almonds

The debittering plays an important role in the processing of bitter almonds,which is a method to reduce the amygdalin contents and potential toxicity in bitter almonds using specific treatment.The traditional method of bitter almond debittering has many drawbacks,such as long time,high energy consumption and large amount of waste water,etc..These methods caused serious waste of resources and environmental pollution.In the context,the ultrasound technology and the response surface optimization design test were used to determine the best conditions of bitter almond debitterizing via ultrasound induced in our studies.Meanwhile,we explored the possible mechanism of almond debitterizing including changes in amygdalin and beta-glucosidase.Our present results showed that ultrasound not only did not lead to epimerization of amygdalin,but also can activate the activity of beta-glucosidase while accelerating the debittering of bitter almond.These results altogether suggesting the ultrasound-induced rapid debitterizing of bitter almonds,as a safe,low-energy and green debitterizing method,could lend new insights into the processing of bitter almonds in food industry.The results obtained are as follows:1.The results of optimization design test of response surface showed that the optimum parameters of ultrasound-induced bitter almond debittering were:ultrasound temperature 55℃,ultrasound power 300 w and ultrasonic frequency 59 kHz.The extraction rate of amygdalin in bitter almonds reached 63.17%at 1 hour of ultrasound time and the liquid ratio was 1:12.The relative error between the prediction and the quadratic model was 0.52%.It shows that the model can simulate the actual dissolution of amygdalin.Simultaneously,Extend the debittering time in subsequent tests so that the bitter almonds can completely debitter.2.Sonication does not result in epimerization of amygdalin to produce L-amygdalin.At the same time,when the bate-glucosidase was present,the debittering efficiency of bitter almonds was higher,and the dissolution rate of amygdalin was as high as 92.38%after 2 hours of ultrasonic debittering,and the debittering effect was good.In addition,benzaldehyde is the most important volatile component in bitter almond and its debittering water,with relative contents of 94.41%and 74.86%,respectively.It shows that bate-glucosidase plays a great role in the debittering process of bitter almond.It shows that bate-glucosidase is a key enzyme in the debittering process of bitter almonds.3.Under the conditions of ultrasound time of 31 min,ultrasound temperature of 50 ℃,ultrasound power of 225 w and ultrasound frequency of 28 kHz,the enzyme activity of bate-glucosidase in bitter almond was the highest(3.64×105 U/g),compared with unsonicated bate-glucosidase,its enzyme activity increased by 34.67%.On the basis of the ultrasonic conditions,bate-glucosidase standard was tested by SDS-PAGE,fluorescence spectroscopy,circular dichroism(CD),differential calorimetry(DSC)and thermogravimetric analysis(TGA).The results showed that the molecular weight of bate-glucosidase in bitter almonds ranged from 48 to 63 kDa,and its fluorescence spectrum redshifted after it was ultrasonicated,indicating that its internal structure and environment have been affected by ultrasound.Simultaneously,according to the result of CD,it can be seen that sonication causes a change in the composition of the secondary structure of bate-glucosidase,leading to an increase in disorder,this conclusion is consistent with the change of enthalpy in the DSC results,which also resulted in loss of more mass of the bate-glucosidase after sonication in the TGA.That is,sonication can alter the internal structure of bate-glucosidase,which will increase its enzyme activity and accelerate bitter almond debittering.