Impact of three warming-up methods on the stability of vitamin C and 5-methyltetrahydrofolate supplemented to apple and carrot purée

•Vitamin C and 5-CH3-H4folate are unexpectedly stable in apple and carrot purée at 80 °C.•None of the tested heating methods led to major losses.•No difference between withdrawal at the surface and bottom position was observed.•Neither did the filling volume impact the degradation pace.

Two methods that are used at people's home to warm-up food namely a microwave and an Actifry® device, and a system that is usually employed in canteen kitchens to keep food warm, were examined on their impact on the stability of vitamin C and 5-methyltetrahydrofolate. The purée was heated until ebullition with the microwave, which lasted 1.5 min. Purée which was warmed-up by the Actifry® device needed around 20 min to attain 80 °C. When the purée was kept warm by a water bath, the vitamin stability was pursued for 180 min at 80 °C. During the latter, stability was examined at the surface and bottom of recipients that were filled with 600 g or 200 g of purée corresponding to a filling height of 5 cm and 1.5 cm respectively. Although vitamin C and 5-methyltetrahydrofolate are usually referred to as heat- and oxygen-susceptible molecules, none of the methods led to major vitamin losses. In terms of the warm holding method, no difference was observed between withdrawals at the surface and the bottom of vessels for neither of the two filling levels. Vitamins were also fairly stable at the surface of recipients where oxygen exposition is high.