加熱處理對臺灣市售蔬菜抗氧化力的影響

Abstract

增加蔬果的攝取有助於降低癌症及其他慢性疾病的發生，主因乃蔬果內富含植化素 (Phytochemicals) 等具抗氧化特性的保健成分。國人在蔬果的攝取上，水果大多是生食，蔬菜則以熟食為主。為瞭解臺灣蔬菜經加熱調理後的抗氧化力特性，本研究利用鐵離子還原抗氧化力檢測法 (FRAP assay) 及氧自由基吸收能力檢測法 (ORAC assay)，對臺灣市售蔬菜進行一系列的抗氧化力分析。 參試蔬菜於生鮮狀態下經較長的均質時間處理後，測得的抗氧化力大都可見有顯著減少的現象。而不同的蔬菜相比較，發生抗氧化力顯著減少所需的均質時間可能不同。此外，參試蔬菜經不同的加熱方式配合不同加熱時間處理後，對於抗氧化力的反應變化會因蔬菜種類及特性而異。一般以水煮和微波水煮的加熱方式對參試蔬菜抗氧化力的提升效果較佳，且此兩種加熱方式的效力相近。若分成瀝水組與未瀝水組，若加熱方式涉及較多的含水量，即會使蔬菜內的抗氧化物大為流失至水中。在不同的加熱方式中，以油炒的加熱方式，對於蔬菜抗氧化力的維持或保留效果較佳。 依蔬菜種類或特性的不同，加熱處理可能具有 (或不具) 增進其抗氧化力的效力，但如要其反應達到顯著的變化，其加熱強度仍需達一定的水準方有其效用，以微波加熱為例，使用的加熱火力最好有中等強度以上。 本項試驗亦使用微波中強度的火力對紅色甜椒等共計 43 種參試蔬菜進行加熱處理，加熱時間均固定為 3 分鐘，同一處理亦同時包含未瀝水 (UWD) 及瀝水 (WD) 的組別，並於加熱處理後測定其抗氧化力 (FRAP與ORAC值)。試驗結果顯示，在兩抗氧化力檢測法的測定下，於未瀝水組 (UWD) 均有顯著增加的參試蔬菜，依提升比例依序包含以下10種蔬菜：綠葉甘藷葉、茴香、紅鳳菜、茼蒿、蕹菜、結球萵苣、青花菜、麻糬長茄、甜豌豆和蘆筍。 綜合上述，若依參試蔬菜對加熱處理的反應變化，選擇合適的調理方式，將可增進該蔬菜內含抗氧化物的攝取含量，亦具有潛在的身體保健效益。

Enriching the intake of fruits and vegetables can help reduce the incidence of cancer and other chronic diseases, the main reason is that phytochemicals which have antioxidant properties and other healthcare contents are abundant in fruits and vegetables. People mostly intake raw fruits and cooked vegetables. To understand antioxidant properties of cooked vegetables in Taiwan, this study use ferric reducing antioxidant power assay (FRAP assay) and oxygen radical absorbance capacity assay (ORAC assay) for a series of antioxidant analysis of commercially consumed vegetables in Taiwan . Fresh tested vegetables after longer homogeneous treatment time, measured antioxidant capacity significantly reduced with longer treatment time. Compare with different vegetables, required homogeneous treatment time on antioxidant capacity occurred significantly reduced phenomenon may differ. In addition, tested vegetables through treatment of different heating methods with different heating time, measured reaction changes of antioxidant capacity may differ with the species and properties of vegetables. Generally speaking, boiled and microwave-boiled heating methods have better effect on enhancing the antioxidant capacity of tested vegetables, and the effect of these two heating methods are similar. To set heating treatment into drained group and not drained group, if heating methods contained more water, which may let tested vegetables lose much antioxidants into the water. Among different heating methods, fried heating method may have better maintained/retained effect on antioxidant capacity of tested vegetables. According to different species and characteristics of vegetables, heating treatment may have (or not have) enhancing effect on their antioxidant capacity, but if their response want to occur significant changes, heating intensity may up to a certain level. To take microwave heating as example, heating firepower up to medium intensity and upward would be better. This study also used medium-high intensity heating treatment of microwave firepower on a total of 43 kinds vegetables, with heating time was fixed in 3 minutes, among same treatment includes drained and not drained groups, measured their antioxidant capacity (FRAP and ORAC value) after foresaid heating treatment. The results show, under determination of two antioxidant assays, significantly increased antioxidant capacity of tested vegetables among drained group on the basis of ranking were following 10 vegetables: green leafy sweet potato vines, fennel, gynura, garland chrysanthemum, water spinach, crisphead lettuce, broccoli, eggplant ‘Ma-Zu’, snap peas and asparagus. To conclude, if select proper processing method according to response changes of vegetables through heating treatment, would enhance intake antioxidants content, and also with potential health-care benefits.