Effects of cooking bananas on their antioxidant components

In Japan, the per capita consumption of fruits remains constant, and bananas rank first in annual consumption. They are commonly stored under controlled temperature and humidity conditions for postharvest ripening. Recent studies reported that the physiological effects of bananas vary with the degree of ripeness, suggesting the potential application of such a variety of effects. The consumption of foods with potent antioxidant properties has been linked to disease prevention. Exhibiting marked antioxidant properties compared with other ordinary food items, bananas can be regarded as a beneficial food for health, yet components responsible for their antioxidant effects have not been fully characterized. Although the fruit is often eaten raw in Japan, cooked bananas are also used as an ingredient in confectionery and other food items. However, changes in their antioxidant activities after heat-processing remain to be elucidated. Therefore, we conducted this study to characterize the antioxidant components of bananas and examine changes in their antioxidant activities after heating. A sample of banana flesh was extracted with methanol, from which alcohol-insoluble solids (AIS) were collected. The DPPH radical-scavenging activity of the banana AIS was markedly higher than that of apple AIS, and the activity increased in a concentration-dependent manner. Bananas contained a markedly higher level of proanthocyanidins than apple. Assessment of the effects of different heating temperatures (25, 60, and 100 degrees C) on the banana AIS showed that the water-soluble extract exhibited higher DPPH radical-scavenging activity when heated at a higher temperature, suggesting that cooking may enhance the antioxidant effects of bananas.