Influence of storage conditions and packaging of fortified wheat flour on microbial load and stability of folate and vitamin B12

•Fortified flours were stored for 6 months at controlled temperature and humidity.•Well-packaged flours were stable up to 6 months whatever the storage conditions.•Vitamins B9 and B12 were mostly affected by the permeability of the packaging.•In low-quality packaging, vitamins were affected by relative humidity variations.•In low-quality packaging, flour microbial quality was impacted when stored at 85% RH. Flour fortification with folic acid (FA) is implemented in many countries, and the fortification of flour with vitamin B12 has been planned. However, vitamins losses can occur during storage. In this study, fortified wheat flour was packaged either in paper bags or multilayer aluminum/PET bags, and stored in controlled conditions of temperature (25 °C or 40 °C) and relative humidity (65% or 85% RH) for 6 months. FA content, cyanocobalamin content, and microbial quality were regularly assessed. In flours packed in multilayer bags (non-permeable to oxygen and humidity), no significant FA and cyanocobalamin losses were observed, irrespective of temperature and RH. In flours packed in permeable paper bags, the microbial quality deteriorated in flours stored at 85% RH, FA loss reached 22–53% after 6 months at 85% RH, whereas cyanocobalamin loss reached 49–63% after 6 months at 65% RH. This shows that, depending on environmental conditions, packaging choice is of critical importance.