Myrosinase activity in different plant samples; optimisation of measurement conditions for spectrophotometric and pH-stat methods

Two substrates with different spectral properties were chosen: sinigrin (SIN) and glucotropaeolin (GTL). For both substrates, the best reliability was achieved at reaction temperature of 37 °C and substrate concentration of 0.2 mM and 5 mM for spectrophotometric and pH-stat methods, respectively. GTL exhibiting higher absorption at the recommended detection wavelength of 230 nm ensured greater sensitivity of spectrophotometric determination of myrosinase activity in the case of transparent plant samples. GTL seemed to increase also the sensitivity of pH-stat method, however, in this case homogenisation of plant samples turned out to be most important. The optimised conditions were then verified for a range of plant samples. Based on these results, the optimised protocols of myrosinase activity determination for both methods are proposed.