On the binding of folic acid to food proteins performing as vitamin micro/nanocarriers

Abstract Folic acid (FA) encapsulation in protein matrices has been reported as a suitable method for preventing FA degradation upon storage or processing as well as to improve its bioavailability. The ability of β-lactoglobulin (β-lg) and type A gelatin (G) to bind FA and form nano/microparticles under conditions of concentration (up to 5% w/w) and pH (3–7) that could have a technological application has been studied. The degree of folic acid binding to the proteins depended on their pH-dependent ζ-potential, indicating the occurrence of ionic bonds. Regardless of FA concentration, the percentage of bound FA to β-lg or G was 100% at pH 3. At pH 3, the size of particles strongly increased by increasing the molar FA/protein ratio. Protein aggregation and further flocculation was observed at higher molar ratios. However, the size of particles could be modulated by high intensity ultrasound application. FA/protein particles formed at pH 3 were totally reversible by shifting back the pH to 7. This pH dependence is strongly favorable for the delivery of FA at the duodene (pH 7) and for the protection of FA at the pH prevailing in the stomach (pH 3).