Aqueous Enzymatic Extraction Of Almond Oil And Protein Hydrolysates

The sweet almond contains a large amount of oil, especially the of which about 70% is oleic acid and 20% is linoleic acid. So the sweet almond oil is nutritious oil. Furthermore, high content of unsaturated fatty acid and proportion of oleic acid and linoleic acid make the oil have favorable nature moist character and be used in cosmetic industry. In this dissertation, the suitable process and the optimum extraction conditions for almond oil and protein hydrolysate were studied, and then the condition of demulsification method,the mechanism of emulsion formed by oil and protein were researched. In the end, the recovery and its antioxidant properties of almond protein hydrolysate was studied.The sweet almond oil and protein hydrolysis were produced using enzymatic hydrolysis method. Complex of cellulose, pectinase (1:2) and Alcalase 2.4L showed better effect than other methods. The optimum parameters for hydrolysis were established by the single factor and orthogonal test. The optimal processing conditions were as follows: seeds/water ratio 1:5(w/w), the amount of cellulose, pectinase was 2.5%(v/w), reaction time 5h; alkaline extraction pH8.5, time 60 min at temperature 60oC; The Alcalase enzymatic treatment was performed at pH10, tempreture 60℃with 1.5% (v/w) enzyme amount for 4h. Under these conditions, the free oil and protein hydrolysates yields were 72.58% and 82.35% respectively. The best conditions of washing precipitate were pH=11, 60min. In this way, the oil percent in left precipitate was 2.5% , and protein hydrolysis 3.0% . After combinating protein hydrolysis produced by washing precipitate with those aquired by enzymatic hydrolysis method together, the total rate of protein hydrolysis was 95.1%. The fatty acid constitution of the almond oil produced by enzymatic hydrolysis method was similar with the oil extracted by solvent at low temperature. to the international standard. The former had higher Saponification value , acid value, lower POV and similar other quality index.In order to enhance the oil and protein hydrolysates yield, the condition of demulsification methods has been studied. Comparing different demulsification methods, such as microwave irradiation, heating, freezing and thawing, standing method, the results showed the effect of freezing and thawing to be the best. The optimum conditions were freezing the emulsion at -18℃for 20h, and thawing for 2h at 40℃and then centrifuging it at 8000 r/min for 20 min, the ratio of demulsification was 42.4%. Still about 14% of the raw material oil existed in the emulsion. So, determinations of functional properties and the composition of sweet almond protein were taken to explain the difficulty of demulsification. The protein's denaturalization temperature is around 83℃, pI=4.5. The determination of functional properties showed that the capacity of absorbing water and oil is better than that of soybean isolate protein. The emulsifying capacity of sweet almond protein was increased as the temperature rose from 20℃to 50℃, and decreased when reaching 60℃, while the stability decreased when reaching 40℃. Surface hydrophobic index of almond protein was much higher than that of soybean protein, which could explain the difficulties in demulsification. Compared with soybean isolate protein, sweet almond protein had worse foaming capacity but similar foam stability. The protein contained four different compositions, in which 77% is albumin. The almond protein's structure was stable and SDS-PAGE revealed that albumin show eleven bands (66100,62800,54200,45700,41100,31200,28600,20400,17200,15100,14400), globin show eight bands (68200,55600,51400,47600,27100,24400,16200和14400), and glutelin show two bands (42000,28600). Because of the large molecular weight and good pliancy, albumin owns good affinity to the interface so that it may play an important part in emulsification.DA201-C macroporous adsorption resin and alcohol were used for purification of the sweet almond protein hydrolysates to obtain desalting sweet almond protein hydrolysates powder. The protein content of the powder was 88%. The percent of the protein hydrolysates with relative molecular weight less than 600Da was 83.17%. The amino acid composition of the protein hydrolysates was similar with almond protein, with high content of glutamic acid. The antioxidative actibities of protein hydrolysates was better with high concentration of protein.