Changes of antioxidant activity and total phenolic compounds during storage of selected fruits

The antioxidant activity and total phenolic compounds in various fruits (common fruits—two varieties of mangoes (ripe and unripe), guava, papaya, mangosteen and banana; and two indigenous fruits—makiang and maluod) were investigated. Banana and papaya showed the lowest activity, and mangosteen, mango and guava exhibited high levels of antioxidant activity (oxygen radical absorbance capacity (ORAC), and ferric-reducing antioxidant power (FRAP)) as well as total phenolic compounds. The studied indigenous fruits (makiang and maluod) are high in both antioxidant activity (ORAC and FRAP) and total phenolic compounds. Three independent batches of selected fruits—guava (Psidium guajava), makiang (Cleistocalyx nervosum var paniala) and maluod (Elaeagnus iatifolia, Linn)—were used to determine the changes in antioxidant activity (AO) and total phenolic compounds (TP) during storage at −20 °C for 3 months and at 5 °C for 10 days. The ORAC-AO during storage at −20 °C for 2 wk decreased significantly in homogenised guava (23%) and in whole fruits of maluod (62%), whereas that of makiang was constant. A continuous decrease in TP was found in homogenised guava throughout the 3-months storage period (69% retention) whereas constant levels were found in other fruits. At 5 °C, a decrease in the ORAC-AO in the whole fruits of makiang (14%) and maloud (70%) was found after a 3-days storage, whereas a gradual increase in the activity (120–190%) was found in the whole fruit of guava throughout the storage period. Among the factors which can affect the levels of antioxidant activity and total phenolic compounds in fruits could be the species, size and texture of fruits, the prepared form of the samples and the conditions of storage (e.g. time, temperature). Preliminary studies on the effect of storage in individual types of fruits are suggested before making a sampling plan for systematic analyses of their antioxidant activity.