Thermal Destruction of Folacin: Effect of Ascorbic Acid, Oxygen and Temperature

Abstract

The effects of temperature and the presence of oxygen and reducing agent on the thermal stability of two naturally occurring labile folates were investigated Microbiological assay of samples heated from 49-100°C for various lengths of time revealed that the loss of S-methyltetrahydrofolic acid in aqueous solution followed first order kinetics with a low Arrhenius activation energy of 9.5 kcal/mole. Tetrahydrofolic acid was extremely labile during heating and the stability of both forms of folate was increased in the presence of ascorbate and nitrogen atmosphere.

Quantification of key folate forms in serum using stable-isotope dilution ultra performance liquid chromatography–tandem mass spectrometry

“…Several preanalytic conditions should be considered to avoid the degradation or interconversion of folates such as adding ascorbic acid, avoiding storage at room temperature and freeze/thaw cycles, as well as exclusion of direct sunlight [20][21][22]. We were interested in studying the stability of folate coenzymes at 4 • C over 24 h with or without ascorbic acid at different pH.…”

Chemical Changes of Vitamins during Food Processing

“…Several kinetic studies have been conducted to examine the thermal stability of various folates in liquid model systems and buffered solutions (Paine-Wilson and Chen 1979;Chen and Cooper 1979;Ruddick et al 1980;Beveridge 1982, 1983;Day and Gregory 1983). Most of these studies have indicated that the degradation of various folates can be described by a first-order kinetic model, although the demonstrated dependence of reaction rate on oxygen concentration indicates that the reaction is pseudo-first order (Ruddick et al 1980;Chen and Cooper 1979;Day and Gregory 1982). The reported activation energy values for thermal degradation of folacin compounds have varied widely (Chen and Cooper 1979;Ruddick et al 1980;Beveridge 1982, 1983), which presumably reflects differences in the temperature dependence of the reactions as a function of environmental conditions and oxygen concentration.…”

“…10-Formylfolic acid exhibits stability comparable to that of folie acid, although it has been shown to be degraded chemically by oxidative cleavage yielding pterin and N-formyl-p-aminobenzoyl glutamate fragments (Maruyama et al 1978;Lewis and Rowe 1979). Several kinetic studies have been conducted to examine the thermal stability of various folates in liquid model systems and buffered solutions (Paine-Wilson and Chen 1979;Chen and Cooper 1979;Ruddick et al 1980;Beveridge 1982, 1983;Day and Gregory 1983). Most of these studies have indicated that the degradation of various folates can be described by a first-order kinetic model, although the demonstrated dependence of reaction rate on oxygen concentration indicates that the reaction is pseudo-first order (Ruddick et al 1980;Chen and Cooper 1979;Day and Gregory 1982).…”

Folic Acid - The Occurrence and the Role in Human Nutrition

“…at _____________________________________________________________________________________________________ 100 o C, respectively. The stability of both folate derivatives drastically increased with the incorporation of ascorbic acid, thus showing the detrimental effect of molecular oxygen at higher temperatures (Chen & Cooper 1979). Folate compounds are susceptible to light.…”

“…The presence in foods of antioxidants (ascorbic acid) and reduced thiols protects folate against oxidant instability. Moreover, exposure to the peptic acid of the stomach increases folate instability (Malin 1977, Chen & Cooper 1979. Polyglutamylation of folate is probably necessary to concentrate and store folates in tissues.…”