Vitamin A Loss Kinetics in Stored Fortified Food: A Storage Bound for School Feeding Programmes

This paper derives a storage bound for vitamin A (retinyl palmitate) in a fortified staple used by school feeding programmes. The staple modelled is fortified cooking oil; fortified flour is treated only as a comparison, because its published losses are larger. Degradation is modelled as first-order kinetics with an Arrhenius temperature dependence and multiplicative light and oxygen exposure factors, using published rate ranges stated in full. The central rate constant is 0.005 per day at 25 °C for oil kept dark and sealed (published range 0.002–0.012 per day), with an activation energy of 60 kJ/mol (range 40–80 kJ/mol). Against a delivery criterion that the dose reaching the child must be at least 70% of the nominal fortified level, the maximum storage time is 71.3 days at 25 °C, 47.9 days at 30 °C, 32.5 days at 35 °C and 22.4 days at 40 °C, in each case dark and sealed. For a stated 90-day mixed supply chain (14 days of transport at 35 °C, 60 days in a warehouse at 32 °C, 16 days in a school store at 30 °C with weekly opening), retention is 36.9%, so guaranteeing the full nominal dose at the point of serving requires fortifying at 2.71 times the nominal level at packing. The active-ingredient cost of that overage is US$0.0231 per child per year on top of a nominal fortification cost of US$0.0135 per child per year, for a stated ration of 10 g of oil per school day over 180 school days. Three failure cases are printed at full size: a clear container in daylight at 35 °C crosses the 70% line in 9.3 days; the same container opened daily crosses it in 3.7 days; and a 180-day chain at 35 °C retains only 13.9% even when dark and sealed, so that no overage within a stated practical ceiling of three times nominal can guarantee the dose. The bound is a planning limit for procurement and warehousing, not a measurement of any actual consignment.