Cell free supernatant of the selected LAB strainswas obtained by centrifuging the culture broth at 10,000 g for 10 min at 4 C, adjusted to pH 6.5 with 1 mol equi/L NaOH followed by filtration through a 0.22 mm pore size filter. To eliminate the effect of hydrogen peroxide, catalase was added at a final concentration of 1 mg/mL to the supernatant broth and the remaining activity determined as described earlier.