牛初乳酪蛋白與乳清蛋白之抗氧化性   全文下載

Antioxidant Properties of Caseins and Whey Proteins from Colostrums

本研究以不同時間（第1~7 天）產出之牛初乳為原料，利用酸沉澱法分離出酪蛋白與乳清蛋白，經冷凍乾燥後，分別以0.1 M 及0.05 M磷酸鈉緩衝溶液（pH 7.0）加以溶解，並進行電泳與抗氧化活性分析。抗氧化活性測定項目包括還原力、亞鐵離子螯合能力、DPPH（α,α-diphenyl-β-picrylhydrazyl）自由基清除能力及抑制脂質過氧化能力等四種，並與BHA（butylated hydroxyanisole）、α-生育醇或EDTA（ethylenediamine tetratacetic acid, 2 Na-salt）之抗氧化性做比較。結果發現，還原力方面，乳清蛋白有強的還原力，在濃度為20 mg/mL 時約為酪蛋白溶液之3 倍。在亞鐵離子螯合能力方面，酪蛋白與乳清蛋白之螯合能力均有隨著樣品濃度增加而提高之趨勢，其中以第1 、2 天之乳清蛋白之螯合能力明顯較強。在DPPH自由基清除能力方面，酪蛋白與乳清蛋白均有隨著樣品濃度增加而提高之趨勢，其中又以第2~4 天之乳清蛋白和第2 天之酪蛋白具有較高的自由基清除能力，在濃度為20 mg/mL時，其清除能力皆高於60%。在抑制脂質氧化能力方面，酪蛋白之抑制效果高於乳清蛋白，於8 小時內其抑制效果與BHA及α-生育醇相當。"

The bovine colostrums collected within 7 days postpartum were used to prepare caseins and whey proteins. The caseins and whey proteins obtained by acid precipitation were freeze-dried and then dissolved respectively in 0.1 M and 0.05 M sodium phosphate buffer (pH 7.0) for electrophoresis and antioxidant activity analysis. The antioxidant activities, including reducing power, ferrous ion chelating ability, α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging activity and inhibitory effect on lipid peroxidation, were measured and compared with α-tocopherol, butylated hydroxyanisole (BHA) or ethylenediamine tetraacetic acid (EDTA, 2 Na-salt). Results showed that whey proteins at a concentration of 20 mg/mL had triple reducing power as that of the caseins. As for the ferrous ion chelating ability, both caseins and whey proteins exhibited increasing chelating ability as protein concentration increased. The whey proteins obtained from the colostrums collected on the first two days apparently exhibited relatively higher chelating ability. Similarly, DPPH radical scavenging activity of caseins and whey proteins increased as the protein concentration increased. Whey proteins from the colostrums collected between the second and the fourth days (Whey proteins 2, 3 and 4) and the caseins from the colostrums collected on the second day (Casein 2) had relatively higher radical scavenging activities, higher than 60% at a concentration of 20 mg/mL. The inhibitory effect on lipid peroxidation of caseins was higher than that of whey proteins, and was comparable to those of α-tocopherol and BHA within 8-hour reaction.