Thermal inactivation of lipoxygenase in soya bean using superheated steam to produce low beany flavour soya milk.

Time and temperature parameters of superheated steam (SHS) treatment were optimised using response surface methodology (RSM) for specific lipoxygenase (LOX) activity in soya beans and crude protein content in soya milk. The optimal SHS treatment was obtained at 9.3 min and 119 °C. The predicted values of specific LOX activity and crude protein content by RSM were 0.0098 μmol/(min mg protein) and 3.2%, respectively. These values were experimentally verified to be 0.0081 ± 0.0002 μmol/(min mg protein) and 3.0 ± 0.1%, respectively. Sensory evaluation showed that the beany flavour of soya milk produced from SHS treated soya beans was significantly weaker (P < 0.05) than that of untreated soya beans. The results showed that the optimised SHS treatment could reduce the beany flavour in the soya milk significantly (P < 0.05) by reducing the specific LOX activity in the soybean, while ensuring the crude protein content in the soya milk complied with Malaysian Food Regulations 1985.