Aqueous Enzymatic Extraction Of Walnut Oil And Functional Properties Of Walnut Meal

Walnut is well known for its nutrition value. Walnut oil contains large numbers of unsaturated fat acid. At present, walnut oil mostly get from pressure technology, walnut protein is difficult to use. The walnut sold on the shannxi market as test material, the main factors that affected the oil extraction rate are analyzed; researche about technology for aqueous enzymatic extraction based on the process of aqueous extraction; compare the different functional properties of walnut meal get from aqueous enzymatic extraction and aqueous extraction; finally study on the enzymatic hydrolysis of fully defatted walnut meal and the oxidation resistance of enzymatic hydrolysate. The main results and conclusions as follows:1. In the aqueous extraction, the effect of ratio of material to water, stirring time and the effect of centrifugal speed on oil extraction rate reached extremely significant level. The optimum conditions were found as follows: the stirring temperature is 25℃, the stirring time is 4 h, the ratio of material and water is 1:3, the centrifugal rotational speed is 4800 r/min. At this condition the rate of oil extraction is 72.00%.2. In the aqueous enzymatic extraction, the effect of stirring temperature and stirring time on oil extraction rate reached significant level. The optimum conditions were found as follows: dosage of the enzyme 17500U/100g slurry, stirring temperature 55℃, stirring time 3 h, pH 4.5. At this condition the rate of oil extraction is 77.34%.3. The walnut meal get from aqueous enzymatic extraction technology has higher water absorption rate and oil absorption rate than the walnut meal get from aqueous extraction technology. There is no significant difference in protein solubility of two meals. The surface characteristics of two meals are bad.4. The degree of hydrolysis of fully defatted walnut meal get from aqueous enzymatic extraction can go up to 90% of the maximum degree of hydrolysis. The enzymatic hydrolysate had strong activity of scavenging·OH, ABTS+, DPPH and no scavenging activity on superodide anion radical. There is no obvious correlation between hydrolysis degree and antioxidant capacity of enzymatic hydrolysate.5. In the aqueous extraction, when the stirring temperature lower than that of walnut protein denaturation temperature, the oil extraction rate rised with decreasing temperature, when the stirring temperature higher than that of walnut protein denaturation temperature, the oil extraction rate rised with increasing temperature. In the aqueous enzymatic extraction, it is discovered that the oil extraction rate decreased obviously when the walnut was stored at low temperature, the pH value has a great effect on the oil extraction rate, the smaller the solubility of walnut protein, the higher the oil extraction rate.