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  • 學位論文

萃取方法及乾燥熱處理對蓮子心抗氧化能力表現之影響

Effects of different extractions and heat treatment methods on antioxidant ability of lotus plumule

指導教授 : 許秀華
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摘要


本研究以蓮子心(Lotus plumule)為試驗原料,探討新鮮、凍乾及日曬處理後,再以不同萃取方法,包括95%乙醇、冷水及熱水法進行萃取,所得萃取物進行抗氧化成分分析,包括總酚類及類黃酮含量與清除ABTS(2,2'-azinobis-〔3-ethy-lbenzothiazo-line-6-sulfonic acid〕)及DPPH(α,α-diphenyl-β-picrylhydrazyl)自由基的抗氧化能力分析;其次探討乾燥蓮子心再經遠紅外線照射及烘箱熱風處理(110℃,60分鐘)後其抗氧化能力的變化,並將抗氧化能力較高之乙醇萃取物,包括日曬後再經烘箱熱風處理及凍乾後再經遠紅外線處理之蓮子心乙醇萃取物,以0.5%添加量添加至大豆油中,探討其對油脂貯藏安定性之影響及開發添加日曬蓮子心熱水萃取液的麻花卷製品,測定產品中油脂過氧化價(peroxide value,POV)和硫代巴比妥酸值(thiobarbituric acid value,TBA)評估其油脂氧化程度。 研究結果顯示:新鮮蓮子心經不同方法進行萃取,以乙醇萃取物的抗氧化能力最強,其次為冷水及熱水萃取物,乙醇萃取物其總酚類含量為57.75±0.17 mg/g dried weight,為冷水及熱水萃取物的2.73及2.02倍;清除50%自由基所需萃取物之濃度,即為EC50(Effective concentration 50%),EC50值愈低表示其抗氧化能力愈高,在清除ABTS自由基能力方面,乙醇萃取物的EC50為16.33±0.02μg/ml,約為維生素E衍生物(Trolox)的19倍,顯示其乙醇萃取物在清除ABTS自由基能力僅為Trolox的1/19,而乙醇萃取物清除ABTS自由基能力為冷水及熱水萃取物的1.36 至1.47倍;在清除DPPH自由基能力方面,乙醇萃取物約為冷水及熱水萃取物的6倍。經日曬及冷凍乾燥處理的蓮子心,再以乙醇、冷水及熱水等萃取方法,進行萃取,探討乾燥對其萃取物抗氧化能力之影響,結果顯示無論以日曬或冷凍乾燥處理皆會降低其萃取率,但其萃取物的抗氧化能力卻提高,且以冷凍乾燥處理為最佳,凍乾蓮子心乙醇萃取物其總酚類含量較新鮮蓮子心高約2.3倍,而清除DPPH自由基能力為新鮮蓮子心乙醇萃取物的1.41倍。經遠紅外線照射(110℃,60min)的凍乾蓮子心其乙醇萃取物的抗氧化能力較未處理組為高,且達顯著差異性(p<0.05),但日曬蓮子心卻以烘箱熱風處理的對照組可萃取出較多的抗氧化成分及較高的清除自由基能力,與未處理組有達顯著差異(p<0.05);凍乾及日曬蓮子心再經遠紅外線照射處理後其冷水萃取物的萃取率及抗氧化成分均顯著下降,顯示遠紅外線照射處理,無法幫助以冷水方式進行萃取過程中抗氧化成分的釋出;凍乾蓮子心經遠紅外線照射其熱水萃取物的抗氧化能力皆較未處理組高,且達顯著差異性(p<0.05),但日曬蓮子心再經遠紅外線照射處理其熱水萃取物,在抗氧化能力表現上與對照組及未處理組無顯著差異性(p>0.05)。 在食品應用方面,以日曬後經烘箱熱風處理及凍乾後經遠紅外線照射之蓮子心的乙醇萃取物,添加於大豆油中,其添加劑量為0.5%,當儲藏於50℃下21天後,油脂的POV值分別為42.50±0.50 及35.17±0.30 meq/kg,皆較對照組52.17±0.58 meq/kg為低;其TBA值分別為11.49±0.10及10.18±0.10(O.D.535nm),皆顯著較對照組14.10±0.1(O.D.535nm)低,顯示0.5%的蓮子心乙醇萃取物添加具有增進油脂儲藏安定性的作用,且以凍乾再經遠紅外線照射之蓮子心乙醇萃取物較有效降低油脂氧化作用。而添加日曬蓮子心熱水萃取液於麻花卷產品中,儲藏於50℃下14天後,其油脂之POV值為23.33±0.63 meq/kg,顯著低於對照組33.33±0.48 meq/kg;其油脂之TBA值為23.06±0.20(O.D.535nm) 顯著低於對照組28.83±0.10(O.D.535nm),顯示添加日曬蓮子心熱水萃取液於麻花卷產品中可延緩油脂氧化的速率,但隨著儲藏時間的增加,其油脂氧化愈嚴重。

並列摘要


This study takes lotus plumule as materials to get extracts through different extraction methods including, 95% ethanol, cold water and hot water extractions. The lotus plumule materials are fresh and treated by freeze-drying and sun-dried methods. These extracts undergo the analysis of antioxidant ability including the contents of total phenolic compounds and flavonoids, and also the antioxidant ability of scavenging effects on ABTS (2,2'-azinobis-〔3-ethylben-zothiazo-line-6-sulfonic acid〕)and DPPH(α,α-diphenyl-β-picrylhydrazyl). In addition,this study investigates the influence of Far-infrared radiation and oven hot air treatment (110℃,60 min) on antioxidant ability of dried lotus plumule. Higher antioxidant ability of ethanol extracts, including those through oven hot air treatment after being frozen and those through Far-infrared radiation after sun-dried were chosen to add 0.5% extracts into soybean oil in order to probe into the influence stability on oil stability during storage and to develop products of Crispy Twists which is added the extracts of sun-dried lotus plumule. Furthermore, it exams POV (peroxide value) and TBA (thiobar-bituric acid value) to value the levels of the oil oxidation. The results of experiments are as follows. Through different extraction methods, ethanol extracts from fresh lotus plumule showed the highest antioxidant ability, followed by cold water and hot water extracts. The total phenolic contents of ethanol extracts are 57.75 ± 0.17 mg/g dried weight, which are 2.73 and 2.02 times to the contents of extracts from cold water and hot water alternatively. The consistency of extracts for scavenging 50% radical is termed EC50 (Effective concentration 50%). The lowest the EC50 is, the highest the antioxidant ability is. For scavenging ABTS, the EC50 of ethanol extracts is 16.33±0.02μg/ml which is 19 times of Vitamin E derivative (Trolox). The result shows that the antioxidant ability of ethanol extracts is only 1/19 to that of Trolox. Scavenging ABTS radical of ethanol extracts is 1.36 to 1.47 times for those of the extracts from cold water and hot water. Scavenging DPPH radical is 6 times to that of extracts from cold and hot water. Lotus plumule treated both by sun-drying and freeze-drying were extract through ethanol, cold water and hot water, to investigate the influence of drying on antioxidant ability. The result shows that no matter using sun-drying or freeze-drying methods, the extraction rates decrease, but the antioxidant ability enhances. Freeze-drying methods can be the better methods. The ethanol extracts of freeze-drying lotus plumule are 2.3 times to those of fresh lotus plumule. The ability of scavenging DPPH radical is 1.41 times to those of fresh lotus plumule. The antioxidant ability of ethanol extracts for freeze-dried lotus plumule under Far-infrared radiation is higher than that of freeze-dried lotus plumule without Far-infrared radiation, and showing significant different. However, the sun-dried lotus plumule can contract more antioxidant and obtained higher radical Scavenging ability than those of lotus plumule without sun-dried method treatment, showing significant different. Ethanol extracts from lotus plumule treated by sun-drying as well as hot air treatment and through freeze-drying as well as Far-infrared radiation were applied to food. Ethanol extracys were added into soybean oil by 0.5% and then storied under 50℃.At the twenty first day, the values of POV are 42.50±0.5 and 35.17±0.30 meq/kg respectively. The results are lower than of the control sample with the value of 52.17 ± 0.58 meq/kg. The TBA values are 11.49±0.10 and 10.18±0.10(O.D.535nm). They are lower the control sample 14.10±0.10(O.D.535nm). The results show that the ethanol extracts of lotus plumule have the functions of improving the stability of soybean oil. Moremore, the ethanol extracts of lotus plumule treated by sun-dried and Far-infrared radiation can effectively decrease the oxidative. Hot water extracts of sun-dried lotus plumule were added into Crispy Twists and stored under 50℃.At the fourteen day, the POV values were 23.33±0.63 meq/kg . They are lower than those of contrast sample, 33.33±0.48 meq/kg. The TBA values are 23.06±0.2(O.D.535nm) which are lower than those of the contrast sample, 28.83±0.1(O.D.535nm). The results show that extracts of sun-dried lotus plumule can defer the speed of oxidative reaction in the products of Crispy Twists. However, the longer the storage is, the more serious effects on oxidative stability are.

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