‘珍珠拔’番石榴發育期間果實抗氧化能力變化

The Antioxidant Activity of Guava (Psidium guajava 'Jenju Bar') as Related to the Fruit Development

‘珍珠拔’番石榴（Psidium guajava L. 'Jenju Bar'）為臺灣常見具高抗氧化力熱帶水果。本試驗以三價鐵離子還原法測定不同熟度之‘珍珠拔’番石榴之抗氧化力，並分析果肉中維生素C及總酚類濃度，無論以果徑或花後天數評估果實發育程度，都顯示出番石榴果肉抗氧化物濃度大致隨著果實發育程度提高而下降。‘珍珠拔’番石榴夏季與冬季果實由開花至果實成熟分別約需113天與140天，兩季果實抗氧化力及抗氧化物質變化趨勢相似。‘珍珠拔’果實發育期間，雖然果肉抗氧化力以及抗氧化物質濃度因果實膨大而被稀釋，但單一果實之總抗氧化力與抗氧化物則隨果實發育持續累積，成熟夏果之總酚類含量高於冬果，而冬果具有較高之維生素C含量。維生素C濃度於果實接近成熟時有快速上升之趨勢，因此推薦食用較高成熟度果實。 Jenju Bar' guava (Psidium guajava L. 'Jenju Bar') is a common tropical fruit in Taiwan with high antioxidant activity. In the present study, the antioxidant activity measured by ferric reducing antioxidant activity (FRAP) assay, vitamin C, and total phenolic compound content (TPC) in related to fruit maturity was investigated. The antioxidant concentration of guava fruit decreased gradually with the increase of fruit development as estimated by fruit diameter and days after pollination. In 'Jenju Bar' guava, summer and winter crops took 113 and 140 days from bloom to maturity; however, the variations of antioxidant activity and antioxidant content were similar. Although the antioxidant activity and the concentration of phenolic compound in guava fruit decreased along with fruit development due to dilution effect resulting from dramatic fruit expansion, the total antioxidant activity and antioxidant content of single fruit accumulatedcontinuously. The results also showed that mature summer crops had higher total phenolic compound content, but mature winter crops had higher vitamin C content. The accumulation of vitamin C increased dramatically while entering mature phase, and thus the fully matured fruit is suggested for consumption.