Spoilage Against Selling Time: A Temperature-Dependent Decay Model for Leafy Greens and a Break-Even Rule for How Much to Bring to Market

A seller of leafy greens must decide in the morning how much to bring. Too little loses sales while stock is fresh; too much loses saleable quality while it waits. This paper models that trade-off explicitly. Saleable fraction decays exponentially with time since harvest, at a rate rising with temperature according to a Q10 factor. The model yields three outputs. First, saleable fraction by temperature and age, with a half-life of 23.10 hours at 20 °C, falling to 9.24 hours at 30 °C and 5.85 hours at 35 °C. Second, a costing of unsold stock: at 30 °C, bringing 100 bunches against demand of 85 sells 80.23, loses 19.77 to spoilage, and carries an unsold cost of $23.73. Third, a break-even rule: for demand of 85, the computed optima are 90 bunches at 15 °C, 93 at 20 °C, 98 at 25 °C, 107 at 30 °C, and 124 at 35 °C — loading factors of 1.06, 1.09, 1.15, 1.26, and 1.46 times the forecast. A common shortcut, dividing demand by the saleable fraction at mid-market, overstates the quantity at every temperature, by 5 bunches at 15 °C and 49 at 35 °C, because early sales remove stock before it can spoil.