in 30 min. After 30 min incubation, the substrate (30 ll) was added and the assays were incubated for a further 2 h at 37 C, and finally 22 T.T. Dao et al. / Food Chemistry 134 (2012) 21–28 terminated by adding 150 ll of the stop solution (25% EtOH, 0.1 M glycine, pH 10.7). The plates were read in a Spectramax M2e spectrofluorometer with excitation and emission wavelength of 360 and 465 nm, respectively.