The Study Of Bitter Almond Protein Extraction Technology

Based on the advantages of abundant nutrition, amino acids, unique flavor, and beingeasy to digest and absorb, bitter almond protein is widely used in the food processing industry.Alkali-solution and acid-isolation method is traditional protein extraction method, but thestrong alkali always causes protein denaturation and affects protein quality. In this paper,according to the principle that albumin and globulin are soluble in dilute salt solution, throughultrasonic-assisted extraction and microwave-assisted extraction, almond meal protein wasextracted and prepared; Orthogonal experiment and response surface methodology were usedto optimize the extraction process and the best extraction process had been obtained; Theextraction process and functional characteristics of bitter almond protein extracted byultrasound-assisted methodology, microwave-assisted methodology and that obtained byconventional alkali-solution and acid-isolation were compared.1. Using ultrasound-assisted salt solution extraction method to extract degreased almondpowder protein, on the basis of single-factor experiment, the effects of NaCl concentration,solid-liquid ratio extraction ratio, extraction time and temperature on bitter almond proteinextraction ratio were investigated systematically. The results showed that solid-liquid ratio,extraction time and temperature had very significant impact and the impacts were in the orderof solid-liquid ratio> extraction time> temperature. Based on the response surface analysis,the optimum extraction conditions were obtained as follows: concentration of NaCl4.1%，extraction temperature44℃and solid-liquid ratio44:1mL/g, ultrasound power400w,extraction time34min. Under such conditions the bitter almond protein extraction ratio couldbe up to69.1%. Bitter almond protein extraction process which had been carried out byultrasound-assisted salt solution extraction methodology was optimized by L9（34）orthogonaltest and the optimum extraction conditions were obtained as follows: concentration of NaCl3%, extraction temperature50℃and solid-liquid ratio50:1mL/g, ultrasound power400w,ultrasonic extraction twice. Under such conditions the bitter almond protein extraction ratiowas79.6%.2. Using microwave-assisted salt solution extraction to extract bitter almond protein, onthe basis of salt solution extraction, the effects of NaCl concentration, microwave power, solid-liquid ratio and extraction time on bitter almond protein extraction ratio wereinvestigated systematically. The results showed that their significant impacts were in the orderof microwave power> NaCl concentration> extraction time> solid-liquid ratio. L9(34)orthogonal test was used to optimize the extraction process and the optimum extractionconditions were NaCl concentration3%, microwave power240W, extraction time210S,solid-liquid ratio25:1(mL/g). Under such conditions the bitter almond protein extractionratio was60.15%.3. Three extraction methods, including ultrasound-assisted salt solution extractionmethod, microwave-assisted salt solution extraction method and alkali-solution andacid-isolation method were compared and their advantages and disadvantages had beendiscussed. For the purpose of higher extraction rate of protein, alkali-solution andacid-isolation method> ultrasound-assisted salt solution extraction method>microwave-assisted salt solution extraction method. But ultrasonic extraction and microwaveextraction may not destroy protein in the neutral extraction conditions. Usingmicrowave-assisted extraction, the extraction time is short and had high extraction efficiency.The functional properties of bitter almond proteins which were extracted by these methodswere investigated. The protein extracted by ultrasound-assisted salt solution extractionmethod had great nitrogen solubility index and emulsifying capacity. Protein prepared byultrasound-assisted salt solution extraction and microwave-assisted salt solution extractionhad comparative and considerable water-holding capacity, emulsion stability and foamingcapacity. But in terms of foaming stability of protein, both ultrasound-assisted salt solutionextraction and microwave-assisted salt solution extraction were inferior to alkali-solution andacid-isolation method. And proteins extracted by such three methods had similar oilabsorption capacity.