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The influence of high-pressure treatment on the 3 main folate species present in orange juice was assessed under conditions similar to those used in high-pressure pasteurization and sterilization using freshly squeezed orange juice and different model orange juices. The latter were used also to determine the influence of matrix components, pH, and excess ascorbic acid. Excess ascorbate strongly protected folates against pressure and heat. Pressurization at 600 MPa and 80°C affected model juice folates synergistically, and pressure increased the formation of 5,10-methenylfolate. In fresh orange juice, components other than ascorbate additionally stabilized folates, thus pressure preservation and pressure sterilization appeared very feasible.

The effect of the extraction procedure on the total vitamin B content in different food matrices is presented. The use of hydrochloric acid, sulphuric acid and trichloroacetic acid, combined with enzymatic hydrolysis using several commercial enzyme preparations, was tested. The results of two liquid chromatographic methods (isocratic and gradient elution) and those of microbiological assay were compared. Reproducible results were achieved using a mineral acid followed by -glucosidase/acid phosphatase hydrolysis for extraction of the same sample and only a few unknown compounds caused interference in the reversed-phase chromatogram. However, the conversion efficiency of the enzyme preparation should always be checked. The liquid chromatographic method indicated that there was a higher vitamin content compared with the microbiological assay. This is probably due to a lower growth response of Saccharomyces with pyridoxamine and pyridoxal rather than pyridoxine.