A Heat-Labile Isomer of Vitamin a in Cod Liver Oils

Abstract

IT was observed during experiments involving the keeping properties of an individual cod liver oil that the value of E^{1 %}_{1 cm} 328 mμ determined on the un-saponifiable fraction spontaneously increased, on keeping, to a maximum after several weeks, but the total absorption determined directly on the oil did not increase. The oil had an initial E^{1 %}_{1 cm} 328 mμ value of 0.60 when determined on the unsaponifiable matter, and 0.60, 0.62, 0.63, 0.65 and 0.54 after 1, 4, 5, 8 and 14 weeks respectively, whereas the determination on the original oil of 0.70 gave figures of 0.70, 0.69 and 0.67 after 1, 8 and 14 weeks. With tests performed on the oil itself, both by spectrographic means and colour reaction, spontaneous increase in the apparent vitamin A has been noted by others¹ and has been assumed due to extraneous substances such as free fatty acids^2,3.