CULTIVAR DIFFERENCE IN PEEL BLACKENING OF BANANA (MUSA SPP.) FRUIT DURING LOW TEMPERATURE STORAGE

Banana (Musa spp.) fruit of ‘Hom Thong’ (Musa acuminata, AAA genome) and ‘Namwa’ (Musa × paradisiaca, ABB genome) were stored at 4 and 12°C and 85–90% relative humidity. At 4°C, peel blackening was visible on day 2 in ‘Hom Thong’ and on day 4 in ‘Namwa’. Levels of total free phenolics, thiobarbituric acid (TBA)-reactive compounds, and in vitro peroxidase (POD) activity in the peel were not correlated with blackening. A slight increase of in vitro catechol oxidase (polyphenoloxidase) activity occurred from day 0 onward in ‘Hom Thong’ and could explain blackening in this cultivar, but such an increase was not found to accompany blackening in ‘Namwa’. Low temperature storage resulted in a rapid increase of in vitro lipoxygenase (LOX) activity in ‘Hom Thong’, which was correlated with blackening. The later blackening in ‘Namwa’ was not accompanied by rising LOX activity. It is concluded that the early peel blackening in low temperature-stored fruit of ‘Hom Thong’ was correlated with increased LOX activity, which might be close to the cause of the blackening, and increased catechol oxidase activity, which is apparently involved in the blackening reaction. The peel blackening in ‘Namwa’, in contrast, was not correlated with any of the measured parameters.