Investigation on the Thermal Stability of Folic Acid and 5-Methyltetrahydrofolic

Folic acid and 5-Methyltetrahydrofolic acid are two major folate vitamers. Although folic acid is commonly used for food fortification to prevent the incidence neural birth defects, 5- methyltetrahydrofolic acid (5-MTHF) is considered to be more bioavailable than folic acid. Therefore, the fortification of foods with 5-MTHF is under consideration. A comparative study on the thermal stability of folic acid and 5-MTHF in various model liquid food matrices such as milk, soymilk, starch-water and water during boiling and autoclaving at various time intervals was performed. The thermal degradation of 5-MTHF was much severe than folic acid in all food matrices e.g., almost 70% loss in 5-MTHF and 17% loss in folic acid. The average retention of folic acid and 5-MTHF (at 5 heating times) was lowest for starch-water and highest for soymilk. The kinetic data showed that there is no linear decrease in concentration of these vitamins with heating temperatures or heating times indicating other factors besides heat such as dissolved oxygen, nonbuffered system, binding of folates by proteins, entrapment of vitamins and poor recovery during purification might affect the folate loss.