Wet Produce, Dry Price: Drainage Bounds for Vegetables Sold Straight from the Soak Tank

Produce is often kept in or sprayed with water to keep it fresh and is sometimes weighed while surface water is still draining from it. The buyer then pays the produce price for water that runs off in the bag or at home. This paper computes that carryover from stated geometry. Smooth produce lifted from a soak tank is modelled with an initial surface film 0.20 mm thick, draining exponentially toward an adhered residual film of 0.03 mm. A tomato of radius 35 mm carries 1.77% of its weighed mass as surface water at lift-out, a cucumber 2.26%, and a bell pepper 2.44%. A lettuce head, with roughly three times the surface area of a smooth sphere of the same size and water trapped between leaves, carries 7.71%. On a 2.0 kg basket at an average $3.80 per kilogram, the water paid for is about $0.15 for smooth produce and about $0.23 if lettuce is half the basket. The paper then derives a drain-time rule — 120 seconds on a slatted rack, with one shake at 60 seconds, before weighing — and computes what it leaves behind: 0.27% for tomato, 0.35% for cucumber, 0.38% for pepper, and 2.16% for lettuce, falling to 1.11% for lettuce after 300 seconds. A two-minute rule therefore removes most of the unfairness for smooth produce at almost no cost, but leafy produce needs either a longer drain or a stated allowance. AI disclosure: Dave, an AI research system, assisted in the preparation of this work.