Enzyme-aided Preparation Of High Gumminess Bitter Almond Kernel Protein And Its Use In Ham Sausage Making

Bitter almond has rich nutritional value and is a high-quality plant protein resource.However,the natural bitter almond kernel protein(BAKP)has poor gelability,which limits its application in food.In order to improve some functional properties of BAKP,protein modification technology is employed so as to expand its utilization.In this paper,the extraction process of BAKP from bitter almond was optimized by alkali solution and acid precipitation.The preparation process of high gumminess BAKP was optimized by papain restriction enzymolysis combined with transglutaminase(TG)crosslinking,and the resultant modified BAKP was used in the production of ham sausage.The main results are as follows:(1)The alkali aided extraction and acid aided precipitation process for preparing BAKP were established by factorial and response surface experiments as: liquid to material ratio was 14:1,p H was 11.0,extraction time was 70 min,extraction temperature was 49 ?,which gives a protein extraction rate of76.17%.(2)Papain was used for restrictive enzymatic hydrolysis,and the enzymatic hydrolysis conditions was determined for high gelling BAKP hydrolysates: substrate concentration 16%,papain addition 6000 U/g,and hydrolysis time 2 h.Subsequently TG was used for crosslinking the resulting BAKP hydrolysates,with the optimum conditions determined by factorial and response surface experiment: TG addition 16 U/g,cross-linking temperature 38 ?,p H 7.0,and crosslinking time 1.5 h.The final modified BAKP shows a gumminess of 36.42 g,which is 209.43% higher than that of natural BAKP.At the same time,other functional properties of the final modified BAKP are also superior to natural BAKP to varying extents.Scanning electron microscopy(SEM)showed that the microstructure of the final modified BAKP changed significantly to a porous network with a smooth and dense surface as contrasted to the original loose and rough surface of natural BAKP.(3)When the protein contents was 5.0%,the yield of ham sausage was the highest;when the contents of natural BAKP and hydrolyzed crosslinked BAKP were 3.0% and 4.0% respectively,the texture characteristics of ham sausage were better;the brightness and yellowness of ham sausage were higher,while the redness lower compared with the blank control group.Ham sausage added with modified BAKP exhibits significantly increased p H value.Low field nuclear magnetic resonance(LF-NMR)reveals that both bound water and free water in the products added with modified BAKP were transformed into nonflowing water,making it the main form of water in ham sausage.The results of sensory evaluation showed that the ham sausage with modified BAKP had the highest holistic score of 88.60±0.92 when the addition amount was 3.0%,and the highest score was 69.60±1.36 when the addition amount of natural BAKP was 4.0%.Therefore,the quality characteristics of ham sausage with modified BAKP are more appealing.