| In this paper，the fatty acid composition and antioxidant activity of okra seedoil extracted by different methods, microencapsulation of okra seed oil by freezedrying, physicochemical and functional properties of protein isolate extracted fromdefatted powder of okra seed，effects of enzyme type and peptide size on thefunctional properties and antioxidant activities of hydrolysates of okra seed proteinisolate were studied.The most prevalent fatty acid in okra seed oil was linoleic acid, followed byoleic acid, palmitic acid and stearic acid，found that extraction method has nosignificant effect on the composition of the fatty acid. The oil obtained under theextraction temperature of40C, pressure of15MPa and extraction time of50minand CO2flow rate18L/h had the stronger scavenging ability on the DPPH radical,and found that the extraction pressure and time had an impotent effect on theactivity of antioxidant of the oil. The DPPH radical scavenging activity of the oilextracted by screw express is higher than those by SCF-CO2and Soxhlet extraction.Taking microencapsulation efficiency as the main evaluating index, processingconditions were optimized by using a response surface methodology, the optimumprocessing conditions of microencapsulation of okra seed oil were determined asfollows: soybean protein45.8%, lecithin2.0%, the wall and core ratio3.5:1, solidscontent21.2%. At the optimum conditions, microencapsulation efficiency was93.15±0.23%. The characteristics and scanning electron microscope of themicrocapsules were determined. The microcapsule processed by freeze drying wasbetter than that by spray drying, but had low microencapsulation efficiency.Therefore, further study was needed to get a uniform shape, higher encapsulationefficiency microcapsules.Okra seed protein isolate (OPI) was prepared using the methods of alkaliextraction and acid precipitation. The physicochemical and functional properties ofOPI were characterized. The results showed that the OPI had abundant amino acidsand rich in Lue and Val and Phe+Tyr, total essential amino acid was284.58mg/g,threonine was found as the first limiting amino acids for OPI, the ratios of E/T (essentialamino acid/total amino acid) was30.46%and the score of ratio coefficient of amino acidwas33. From the analysis of SDS-PAGE, molecular weights of OPI were from14.4to94.0kDa and the main protein was between20～26kDa. Enzymatic hydrolysates of okra seed protein isolate were prepared bytreatment with alkaline protease (Alk), neutral protease (Neu), trypsin (Try),flavourzyme (Fla). The proteases were used under the optimum hydrolysisconditions (highest enzymatic activity) according to the manufacturers, Alk wasfound to be the most efficient，while Fla and Try were the least efficient. It wasfound that all the hydrolysates had antioxidant activities, hydrolysate prepared by Tryhad the highest ferrous ion chelating activity and prepared by Neu had the highestreducing power. The hydrolysates were further fractionated into peptide sizes of Pr<1,1<Pr<3, Pr>3kDa using membrane ultrafiltration and their membrane ultrafiltrationfractions were assayed for in vitro antioxidant activities. The effectiveness of OPHand their membrane fraction to scavenge free radicals, chelate metals and reducingactivity suggest that these products possess potential as a food source of antioxidant agents.Hence, they could be used as raw materials for the production of peptide ingredients thatcan be used to formulate functional foods and nutraceuticals. They could also be used asnatural source of antioxidants in the food industry to prevent lipid oxidation and maintainfreshness during production and storage of food products. |
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