澳洲坚果果仁氨基酸含量的差异性分析

采用不同蛋白酶水解澳洲坚果粕制备多肽，以ABTS⁺自由基清除率为评价指标，筛选制备抗氧化多肽适宜的蛋白酶。利用DA201-C大孔树脂纯化、超滤膜逐级分离，获得不同分子量澳洲坚果多肽（MNAP-1、MNAP-2、MNAP-3、MNAP-4）组分，并以谷胱甘肽为对照，研究了其对DPPH、羟基、ABTS⁺自由基的清除能力及还原能力。结果表明：制备澳洲坚果抗氧化多肽的适宜蛋白酶为复配蛋白酶，相同浓度下其对ABTS⁺自由基清除能力优于中性蛋白酶、酸性蛋白酶、碱性蛋白酶、木瓜蛋白酶与菠萝蛋白酶。不同分子量澳洲坚果多肽呈现不同的抗氧化效果，其对DPPH、ABTS⁺自由基具有较强的清除作用，具有一定的羟基自由基清除能力和还原能力。其中，MNAP-4（分子量小于1000 Da）的抗氧化活性最好，其对DPPH、ABTS⁺、羟基自由基清除能力及还原能力的半抑制浓度（half maximal inhibitory concentration，IC₅₀）分别为0.36、6.75、0.08、3.19 mg/mL，低于其他分子量多肽。相关性分析得出不同分子量澳洲坚果多肽与其清除DPPH自由基（r=0.947，P<0.01）、羟基自由基（r=0.964，P<0.01）、ABTS⁺自由基（r=0.948，P<0.01）及还原能力（r=0.856，P<0.01）之间存在极显著相关。澳洲坚果复配蛋白酶酶解产物含有抗氧化活性较好的肽类，研究结果可为其抗氧化肽的制备与应用提供一定的理论依据。

Compositional analysis and roasting behaviour of gevuina and macadamia nuts

Macadamia nut polypeptides were prepared by enzymatic hydrolysis of macadamia nut meal, and suitable proteases for the preparation of macadamia antioxidant polypeptides were screened with ABTS⁺ radical scavenging effects as evaluation indicators. Four constituents (MNAP-1, MNAP-2, MNAP-3, MNAP-4) were obtained by DA201-C macroporous resin and dialysis technology. The scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl radical (DPPH·), hydroxyl radical and 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonate radicals) radical (ABTS⁺·), and reducing power were investigated by comparing with glutathione as controls. The results showed that the suitable protease was complex protease for the preparation of macadamia antioxidant polypeptides, which was better than neutral protease, acid protease, alkaline protease, papain and bromelain at the same concentration. Antioxidant activities of different molecular weight macadamia nut polypeptides were different, which all had strong scavenging capacity against DPPH and ABTS⁺ radicals, and also had certain scavenging capacity against hydroxyl radical and reducing power. MNAP-4 (molecular weight less than 1000 Da) had the strongest scavenging capacity against DPPH, ABTS⁺ and hydroxyl radicals and the highest reducing power with half maximal inhibitory concentration (IC₅₀) of 0.36, 6.75, 0.08 and 3.19 mg/mL, respectively, which was lower than other molecular weight polypeptides. Correlation analysis showed different molecular weight macadamia nut polypeptides had good correlations with their DPPH, hydroxyl and ABTS⁺ radicals scavenging capacity and reducing power with r values of 0.947, 0.964, 0.948 and 0.856 (P<0.01), respectively. The complex protease hydrolysates from macadamia nut meal contained good antioxidant activity polypeptides, which could provide a theoretical basis for the preparation and application of antioxidant peptides.