Susceptibility of 5-methyltetrahydrofolic acid to heat and microencapsulation to enhance its stability during extrusion processing

Folic acid is a common form of folate used for food fortification to prevent the incidence of neural birth defects among others. However, 5-methyltetrahydrofolic acid (5-MTHF) is considered, a better alternative to folic acid and is less likely to mask the symptoms of B12 deficiency in older populations. Also it is less bioavailable, and present in very low amount in foods. Fortification of foods with 5-MTHF is considered problematic, because it is highly sensitive to normal food processing operations. A comparative study on the thermal stability of folic acid and 5-MTHF in various liquid model food matrices such as milk, soymilk, starch–water and water during boiling and autoclaving at various time intervals was performed. Thermal degradation of 5-MTHF was more severe than folic acid in all food matrices e.g., almost 70% loss of 5-MTHF vs 17% loss of folic acid. Microencapsulation of 5-MTHF is considered to improve the stability of 5-MTHF during processing. A combination of pectin (P) and sodium alginate (A) at three different proportions (P60:A40, P70:A30, P80:A20) were employed for encapsulating 5-MTHF by spray drying. Microcapsules with the highest loading efficiency of 60% of vitamin (from P80:A20) and unencapsulated 5-MTHF powder was incorporated into starch and extruded at six different temperatures (100, 110, 120, 130, 140, 150 °C). The 5-MTHF had better stability (84–94.5% retention) compared to the free form (65.3–83.2%) in all extruded products. The effectiveness of encapsulation was more evident at higher extrusion temperatures.