| By researching the optimization of the extraction process, the component analysis and the functional features of the protein isolate from the wild apricot in the western part of Liaoning province, the following conclusion was obtained in this paper:1 Almond nutrition and the response surface optimization of extraction technology was studied:(1) Through measuring the almond nutrition component using the National Standard Method, the basic nutrition was constituted by the following part:23.50% of the protein, 48.40% of the fat,9.65% of the carbohyrate,7.54% of the water,2.20% of the ash content; the isoelectric point (pl) of isolated almond protein was 4.30.(2) This research studied the impact of the elements on the rate of isolated protein extraction, such as solvent ratio, pH, ultrasonic time and ultrasonic temperature. And the software of the Design-Expert V.8.0.6 was used to optimize the response surface process conditions for the extraction of almond protein by alkali solution and acid isolation. By analysis, the impact of the elements on the rate of isolated protein extraction was:solvent ratio> pH> ultrasonic time> ultrasonic temperature. The best technical parameter optimized by the response surface were pH 8.7, ultrasonic temperature 33 ℃, ultrasonic time 46min, solvent ratio 1:5g/mL. In this condition, the extraction rate of isolated almond protein was 85.80%.2 Almond protein classification preparation and protein component analysis:(1) The almond protein components was prepared on the method of grade based on the traditional Osborne, then four kinds of protein components was obtained as follow:47.2% of albumin,39.76% of glutelin,9.62% of globulin,1.01% of alcohol soluble protein, which suggested that the main section of almond protein was 87% of albumin and glutelin.(2) By analyzing almond protein component based on SDS-PAGE cataphoresis, it was suggested as follow:The sub molecular weight of separation protein and glutenin protein distribution between 17ku to 58ku, albumin sub molecular weight distribution between 16ku to 123ku, mainly concentrated on 16ku and 42ku near base, more concentrated distribution; globulin sub molecular weight distribution between 7ku to 51ku, sub configuration is uniform; gliadin only two sub bands, and molecular weight distribution between 17ku to 43 ku.(3) The almond protein components were analyzed using the Fourier transform infrared spectroscopy. Through the spectrum, it was found that the infrared absorption peak of these four kinds of protein all appeared in 1700-1600cm-1,1600-1500cm-1 and 1200-1300cm-1; those were the protein absorption peaks,he secondary structure of almond protein was based on β folding, respectively as 31.42% of isolated protein,33.58% of glutelin,36.46% of albumin,35.75% of globulin.the structure of globulin and albumin is more stable than that of glutelin and isolated protein in four kinds of protein.(4) By determining the amino acid content of the protein component and assessing the amino acid nutrition by automatic amino acid analyzer, the results showed that:the isolated almond protein and the components of four kinds of protein had abundant essential amino acid whose pattern got closer to the one based on FAO/WHO. On the other side, about the non essential amino acid, the isolated almond protein and the components of four kinds of protein also had abundant glutamic acid, arginine and aspartate, which has some positive effect on the body. Through assessing the parameter of the almond protein nutrition (E/T value, amino acid score, PER), it could be found that the isolated almond protein, albumin and glutelin are high-quality protein resource, which had the higher amino acid score and PER values, and the methionine was the first restrictive amino acid of the isolated protein and the components of four kinds of protein.3 Through researching the functional characteristics of the isolated almond protein and analyzing the effect of these elements on the functional characteristics, such as pH, the concentration of protein, temperature and so on:(1) The isolated almond protein had the minimum solubility near the isoelectric point. And the solubility of protein decreased gradually as the pH value increased on pH<pl; meanwhile the solubility of protein increased gradually as the pH value increased on pH>pl. The solubility under acidic conditions was less than the one under alkaline conditions.(2) As the pH value raised, the water binding capacity of isolated protein first decreased and then increased, and reached a minimum near by the isoelectric point of protein; and it increased first and then decreased as the temperature increased. The best water binding capacity could reach 3.544g/g on the condition of the temperature of 50℃ and pH=9.(3) The oil absorption of the isolated almond protein would decrease as the temperature increased. The oil absorption of the isolated almond protein was worse than the one of isolated peanut protein, but better than the one of isolated walnut protein.(4) The emulsifiability and emulsifying stability of isolated almond protein reached a minimum close to the region of the isoelectric point. On the left side of the region of the isoelectric point,the emulsifiability and stability decreased as the pH increased; on the right side of the region of the isoelectric point, the ones increased as the pH increased. The emulsifiability also had positive correlation with the density of the protein, that is, the higher the density was, the better the emulsifiability was, the more helpfully the emulsifying stability was kept.(5) The foamability and foam stability of isolated almond protein had positive correlation with the density of the protein, that is, they heightened as the density increased; and the foamability reached a minimum at pH=5, meanwhile, the foam stability reached a maximum. Outside the isoelectric point, the foamability increased and the foam stability decreased as the pH changed. |
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