Browned compounds were quantified by measuring the absorbance of the sample at 420 nm after exactly 1 min, in a 3 mL capacity cuvette (1 cm length) with a Lambda 25 UV–VIS spectrophotometer (Perkin-Elmer Instruments, Madrid, Spain) connected to a thermostatically controlled chamber (25 °C) and equipped with UV Win-Lab software (Perkin Elmer).