- 學位論文
巨峰葡萄（Vitis labruscana）之外皮與種子的體外抗氧化成分分析、數學模式建立及功能性食品之應用
In Vitro Antioxidant Analyses and Mathematical Modeling on Kyoho Grape (Vitis labruscana) Skin and Seed for Functional Food Applications
摘要
巨峰葡萄Kyoho（Vitis labruscana）因果實肥碩、鮮嫩甜美，在台灣有相當高的接受度。北美葡萄（Vitis aestivalis）是一種進口釀酒品種，與巨峰相比，價格較高，在台灣，此兩種葡萄常拿來釀酒以及家庭食用。其副產品（果皮和種子）一向被視為農業廢棄物，因含多酚化合物，近年來受到食品加工業重視。本研究利用巨峰葡萄與北美葡萄兩者之果皮、果實及果肉萃取物作為樣品，以DPPH自由基清除活性和ABTS自由基清除活性為指標，經多變量和非線性統計分析，挑選最適樣品。接者，以數學模式來探討和預測不同乾燥溫度對該萃取物的物理化學特性與機能性成分的影響。最後則探討葡萄果皮萃取物的機能性成分，使用於製作水中油（oil-in-water）的乳化劑和機能性茶飲的可能性。結果顯示，在巨峰葡萄萃取物當中，酚類化合物（沒食子酸、表兒茶素、兒茶素）會貢獻77.91 %的抗氧化活性，但在北美葡萄萃取物樣品中則具有較高的DPPH 抑制能力（97.26 %）。經主成份分析（Principle component analysis, PCA）了解兩樣品之區分以表兒茶素為主要因子，其變異數的解釋能力達到91.35 %，是一種用於評估兩個品種之間酚類成分（例如 (-) -表兒茶素）異同點的合適方法。進一步研究顯示，活性化合物表兒茶素在不同溶劑中的溶解度會隨著溫度的變化（298.15到338.15 K）而提升。本研究另發展出一估計抗氧化活性的方法（dropping DPPH），分別使用線性法和內插法，對樣品葡萄萃取物之半有效濃度（EC50）進行計算，發現預測值和實際值有一定相關性（R2 ≥ 0.96），且成本較低，故可取代傳統DPPH之測定方式。經儲藏二十天後，經由數學模式發現，巨峰葡萄種子和果皮會隨著乾燥溫度增加而降低水分含量。且該萃取物具有抗氧化能力，其DPPH清除率高達93 %，且在含有p-anisidine類似物（4.30-20.71 mg MDA/L）和TBARS（6.08-11.15 mg MDA/L）水中油的樣品中，其抗油脂氧化能力和標準品（維他命C和沒食子酸丙酯）相比，效果相似。巨峰葡萄皮的機能性茶飲，經實驗發現，有極低的卡路里（0.21-0.46 cal/g），且含有少量之蛋白質和脂肪 （0.04-0.22 mg/g和0.09-0.45 %）。茶飲品亦具有DPPH清除能力（清除率達49.80-81.81 %），且總酚、類黃酮和花青素含量約分別為0.08-0.14 mg GAE/mL、 0.04-0.10 mg QE/mL和0.27-0.56 mg/100 mL。此機能性茶飲（在40 % 至50 % 乾燥者）的感官品評結果，可為大眾接受（> 6）且色澤誘人（> 6）。綜合上述，本研究結果顯示，統計方式可以用於篩選葡萄品種，並開發了一種具較低成本的方法來測定抗氧化力和半有效濃度。本研究的數學模式可用於開發巨峰葡萄籽與皮的新型功能性食品。而該巨峰葡萄附產品開發的方法，未來可應用於其他食品之研究。
並列摘要
Kyoho (Vitis labruscana), a commercial grape cultivar developed in Taiwan and attractive for its large berries, has high quality and acceptability in local food markets. American wild bunch grape (Vitis aestivalis) is a non-traditional imported variety and is higher-priced compared to Kyoho. These two varieties are mostly used in Taiwan for wine processing and household consumption. However, the grape skins and seeds are discarded as eco-friendly agricultural wastes and are attractive sources of polyphenolic compounds, which has led to a renewed interest in the food processing industry. Therefore, these two cultivars were compared using multivariate statistical techniques. Advanced statistical methods were employed to determine the in vitro antioxidant activities for Kyoho cultivar skin, seed, and flesh extracts by DPPH• and ABTS• assays. Moreover, the effects of drying temperature on physico-chemical and functional properties of Kyoho (seeds and skins) were evaluated by mathematical models; and the functional food potential of grape skin extracts were investigated in an oil-in-water (O/W) emulsion and Kyoho skin functional tea beverage. The results revealed variations in phenolics (gallic acid, epicatechin, and catechin) that were attributed to higher total antioxidant (77.91 %) radical scavenging activities of Kyoho grape extracts; however, higher inhibition capacity by DPPH• (97.26 %) was determined for American wild bunch grape extracts. The results of principal component analysis (PCA) reported 91.35 % of the total variance, which was a suitable approach for evaluating similarities/dissimilarities between both cultivars in terms of phenolic compositions (e.g., (−)-epicatechin). Therefore, in-depth studies on solubility of bioactive compound ((−)-epicatechin) revealed experimental solubility of (−)-epicatechin in pure solvents increased with increasing temperatures (298.15 to 338.15 K). The findings from the prediction of EC50 values of grape extracts reported deviations using linear regression and direct interpolation methods. Moreover, dropping DPPH• method was the alternate suitable method for the estimation of antioxidant activity (R2 ≥ 0.96). Kyoho seeds and skins reported decreased experimental moisture ratio with an increase in drying temperature. Kyoho skin extracts exhibited > 93 % inhibition and reported a similar p-anisidine (4.30 to 20.71) and TBARS (6.08 to 11.15 mg MDA/L) compared to standards during 20-day storage. Kyoho skin functional tea reported no caffeine with negligible protein (0.04 to 0.22 mg/g), fat (0.09 to 0.45 %), and calories (0.21 to 0.46 cal/g). Total phenolic and flavonoid contents ranged from 0.08 to 0.14 mg GAE/mL and 0.04 to 0.10 mg QE/mL, respectively with antioxidant activity (49.80 to 81.81 %) and anthocyanins (0.27 to 0.56 mg/100 mL). The sensory evaluation of Kyoho skin functional tea (either of 40 and 50 % addition of Kyoho skin) rated as acceptable (> 6) with attractive color (> 6). Overall, the results suggested that the application of multivariate statistical techniques provided deeper understanding on assessment of grape cultivars. In addition, our findings showed implications for selecting a cost-effective method to determine antioxidant (dropping DPPH• method) and EC50 values. Drying models could be used to develop novel functional foods from Kyoho (seed and skin) for use in food processing industries. Studies that examine the chemometric optimization methods for grape waste and its applications should be investigated in the future for the progress of science within the field of food science and technology.
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