Flavonoids are naturally-occurring polyphenolic compounds that form acid labile complexes in aluminium chloride colorimetric method (Mabry et al., 1970). In this study, significant enhancement (3%) in extractability of flavonoids was observed in UV-C treated juice sample, U15 (9.02 mg CE/100 ml) when compared to the control (8.74 mg CE/100 ml).The exposure of UV-C light stimulates the formation of free radicals which may trigger stress responses such as accumulation of phytoalexins. As a result, there is an increase in the level of flavonoids related to a defence mechanism(Alothman et al., 2009). However, for U60 samples, degradation of flavonoids was observed. This could be attributed to the longer UV-C exposure time which induces too much stressthus, suppressing flavonoid content. Besides that, thermal treated samples exhibited significant reduction (25%) in total flavonoids.