Thermal Stability of Folic Acid and 5-Methyltetrahydrofolic Acid in Liquid Model Food Systems

The effects of temperature, iron and ascorbate fortification, and oxygen concentration on the stabilities of folic acid (FA) and 5- methyltetrahydrofolic acid (5-CH₃-THF) were examined in liquid model food systems. Small retort pouches were used as reaction vessels and the model systems were processed at 100°C, 120°C, and 140°C. A cation-exchange procedure was devised to provide sample extract purification before quantitation using high-performance liquid chromatography (HPLC). FA and S-CH₃-THF were found to be very stable under these conditions. Lactose, protein, iron and ascorbate were all found to be capable of reducing the oxygen partial pressure within the model systems, thereby enhancing the stability of FA and 5-CH₃-THF. FA and 5-CH₃-THF degradation was not zero or first order but possibly second order as a result of limiting oxygen concentrations.