Under anaerobic conditions in the media, folates were not degraded irrespective of the temperature applied (45, 65 or 85 °C) neither in spinach, green bean purees or in model solutions. The presence of 40 kPa of oxygen led to folate loss. Clearly oxygen was a factor for folate degradation during thermal treatment. However, the rate of folate loss was not doubled compared to our previous experiment under atmospheric (21 kPa oxygen) condition. Therefore, the exact role of oxygen (catalyst or reagent) and its stoichiometry still needs further investigation.