Nonenzymatic Browning in Pear Juice Concentrate at Elevated Temperatures

Abstract

ABSTRACT The effect of temperature and soluble solids (°Brix) on nonenzymatic browning in pear juice concentrate was determined by following absorbance at 420 nm (A 420 ) over the temperature range of 50–80°C. Browning could be modeled as a zero order rate process with rates of 22.2 × 10 −4 (45.2 °Brix), 36.9 × 10 −4 (55.4 °Brix), 53.5 × 10 −4 (65.1 °Brix) and 107 × 10 −4 (72.5 °Brix) A 420 · min −1 at 80°C. Temperature dependence was described by the Arrhenius relationship with an average activation energy of 21.9 kcal · mole −1 . Formol titration indicated a 20% loss of amino acids during heating 4.4 hr at 80°C and no loss of carbohydrates was observed after any heating period.