Folates play a key role in human one-carbon metabolism and are provided by food. It is well established that folates are beneficial in the prevention of neural tube defects and cardiovascular and neurodegenerative diseases. Fruits and vegetables, and especially green vegetables, are the main sources of folates. In parallel, fruits and vegetables, with high contents of folates, are mostly consumed after processing, such as, canning, freezing, or home-cooking, which involve folate losses during their preparation. Hence, it is important to know the percentage of folate losses during processing and, moreover, the mechanisms underlying those losses. The current knowledge on folate losses from fruit and vegetables are presented in this review. They depend on the nature of the respective fruit or vegetable and the respective treatment. For example, steaming involves almost no folate losses in contrast to boiling. Two main mechanisms are involved in folate losses: (i) leaching into the surrounding liquid and (ii) oxidation during heat treatment, the latter of which depending on the nature of the vitamer considered. In this respect, a vitamer stability decreases in the order starting from folic acid followed by 5-HCO-H 4 folate, 5-CH 3 -H 4 folate, and, finally, H 4 folate. Further studies are required, especially on the diffusion of the vitamers in real foods and on the determination of folate degradation products.

The study comprises a systematic and quantitative evaluation of potential intrinsic and extrinsic factors that impact vitamin C degradation in a real food matrix. The supernatant of centrifuged apple purée was fortified in vitamin C, and degradation was followed without stirring. Model discrimination indicated better fit for the zero order model than the first order model which was hence chosen for determination of rate constants. pH influenced strongly vitamin C degradation in citrate-phosphate buffer but not in the apple purée serum. To get an idea of the impact of the food matrix, stability in apple purée serum was compared with that in carrot purée. In the latter, stability was slightly higher. Vitamin C degradation rates were not influenced by its initial concentration. The temperature effect was only marked in the temperature range 40-60°C. In the range 60-80°C, filling height of tubes had the greatest impact.

a b s t r a c tOxygen availability in different media during heat treatment (8 h at 80 C) and the related vitamin C loss was assessed. Dissolved oxygen in water containing 3 mmol kg À1 of ascorbic acid decreased initially and seemed to be replaced by oxygen from the headspace in the course of time, as oxygen values increased again. In apple pur ee and carrot pur ee in contrast, oxygen was depleted within 60 min. Vitamin C in ultrapure water was stable even in the presence of oxygen. A trigger seemed to be crucial to launch vitamin C degradation. Fe 3þ ions added to water, but also the media Mc Ilvaine citrate-phosphate buffer (pH 3.5) or apple pur ee, initiated degradation. Adding Fe 3þ ions to apple pur ee did not accelerate vitamin C degradation but shifted the equilibrium between ascorbic acid and dehydroascorbic acid to the latter. Oxygen deprivation stabilized completely vitamin C, independently of the medium tested. A temperature decrease to 70 or 60 C, in contrast, had no effect on the degradation extent of vitamin C in water containing 20 mmol kg À1 Fe 3þ ions but led to complete stability in apple pur ee.

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. Impact of three warming-up methods on the stability of vitamin C and 5-methyltetrahydrofolate supplemented to apple and carrot purée. LWT -Food Science and Technology, Elsevier, 2017, 84, pp.668-673. 10.1016/j.lwt.2017 Version postprint a b s t r a c tTwo 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 pur ee was heated until ebullition with the microwave, which lasted 1.5 min. Pur ee which was warmed-up by the Actifry ® device needed around 20 min to attain 80 C. When the pur ee 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 pur ee 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.