Why a cheaper ingredient can cost more per portion

Test the ingredient that creates the uncertainty

Start with one product whose usable amount varies: vegetables needing substantial trimming, meat that loses weight during cooking, or a product sold in liquid that is drained away. Keep the question narrow. You are trying to establish what the kitchen gets from a purchase under its normal process.

Use the same specification and preparation method for each comparison. A raw trimmed weight cannot be compared directly with a cooked serving weight. Record the point of measurement, equipment, batch size and who prepared it. BCcampus's yield-testing chapter explains the distinction between purchased and usable quantities.

Further reading: BCcampus: Yield Testing

Work through a complete example

Consider two hypothetical packs of the same ingredient for the same dish. Pack A costs £18 for 5 kg, and your preparation produces 3.6 kg usable product. Pack B costs £20 for 5 kg and produces 4.2 kg. A appears cheaper at £3.60 per purchased kilogram, compared with £4 for B.

The usable cost reverses the comparison: £18 ÷ 3.6 = £5 per usable kilogram for A; £20 ÷ 4.2 is about £4.76 for B. At a 150 g usable portion, the ingredient cost is 75p for A and approximately 71p for B. These figures exclude other ingredients, labour and energy.

One test does not establish the normal yield. Repeat across deliveries and cooks, especially where natural variation is high. If B needs much more preparation time or gives a poorer result, the lower usable ingredient cost may still be the wrong operational choice.

Do not make every trimming a failure

Some loss is part of producing the dish safely and to the required quality. Separate necessary preparation loss from avoidable mistakes such as excessive trimming or an incorrectly prepared batch. A target based on perfect laboratory handling may encourage staff to leave unsuitable material in the finished product.

If a by-product has a genuine approved use, record that use rather than assuming it is worthless. But do not credit an imaginary sale or stockpot that never happens. Allocate shared costs consistently and avoid counting the same input as a full cost in two dishes. For a simple first test, keep the by-product visible and ask your bookkeeper how you want to treat it.

Put the result into the recipe and count sheet

Update the recipe with both the purchased quantity and expected finished output. A cook preparing the dish needs to know the output to aim for; the person ordering needs to know the input to buy. Use consistent units so a kilogram of raw product is not mistaken for a kilogram of prepared stock.

Add a review trigger when the supplier, grade, pack size or cooking method changes. Keep the original test sheet so the next manager can see why the recipe cost differs from the invoice price. If a batch comes out well below the expected range, investigate the process before changing the standard.

The Reddit discussion about inventory detail includes uncertainty over counting bulk prep. That problem connects directly to yield: if you do not know what a batch contains and produces, its stock value will be a guess. Measure one important batch properly before extending the method across the menu.