Usefulness of some Maillard reaction indicators for monitoring the heat damage of whey powder under conditions applicable to spray drying

The Maillard reaction (MR) rate was observed according to available lysine loss, furosine, hydroxymethylfurfural (HMF), furfural, and brown colour during the heating of freeze-dried nano-filtered whey at 60, 75, and 90 °C and water activities of 0.11, 0.33, 0.43, and 0.73. The physical state of lactose was measured and associated with MR rate. The values obtained for available lysine, furosine, HMF and browning index ranged between, respectively, 11.3 and 1.63 (g 100 g^?1 protein), 0.44 and 11.1 (g 100 g^?1 protein), not detected and 57.7 (mg 100 g^?1 protein) and 0.0104 and 0.1707. The greatest heat damage occurred with low moisture content and high temperature. The MR rate was influenced by the physical state of lactose, heating temperature and the moisture content of the whey. This occurred to a greater extent during the initial and intermediate stages of the MR as opposed to during the formation of coloured compounds.