Vol. XXXI · The Professional Kitchen Plate 4 of 11yield, trim, as purchased, AP, edible portion, EP, yield test, butchery yield, fish yield, vegetable trim, cost per edible kg, ordering, waste, by-products, stockTF

Yield and Trim.

A whole salmon at 12 per kilo looks cheaper than fillet at 26. With a 50 % yield, its fillet costs 24 — and the head and frame make a stock.

Every ingredient arrives with parts that will not be served. The yield percentage is the edible portion as a share of the weight purchased: onions about 90 % after peeling, carrots about 85 %, broccoli about 60 % as florets, a whole chicken about 55 % as boneless meat, a whole round fish about 50 % as skinless fillet, a bone-in rib about 65 % trimmed. Kitchens measure their own yields with a yield test: weigh the product as purchased, break it down as it will be used, and weigh each part — edible portion, usable by-products (bones for stock, trim for staff meals) and true waste.

Two calculations follow. To serve a given edible weight, buy AP = EP ÷ yield. And the true cost of the edible food is the AP price ÷ yield, plus the labour of breaking it down. A whole fish or carcass can still be the better buy if its by-products are used — frames and heads for stock (XXII.1), trim for terrines or staff food — and if the kitchen has the skill and time; pre-cut products cost more per kilo but save labour and waste. Cooking adds a second yield loss (water and fat, XVIII.3), which costed recipes take into account. The workshop buys for a yield.

Below: for the item you choose and the edible portion you need, the as-purchased weight to order and its cost, and the cost per edible kilogram, from typical yields and illustrative prices (¤ per kg).

What you will learn
Workshop
Typical raw yields (teaching values within published kitchen yield guides): whole round fish to skinless fillet 50 %, whole chicken to boneless meat 55 %, bone-in rib to trimmed boneless 65 %, broccoli to florets 60 %, onion peeled 90 %, spinach picked 75 %. Illustrative AP prices (¤/kg): salmon whole 12, chicken whole 6, rib 30, broccoli 4, onion 1.6, spinach 6. Exact: AP = EP ÷ yield; EP cost = AP price ÷ yield.

Buy for the yield, use the rest

For 10 kg of salmon fillet at a 50 % yield, a kitchen must buy 20 kg of whole fish; at 12 ¤/kg as purchased, the fillet really costs 24 ¤/kg — close to the 26 ¤/kg of ready fillet. The whole fish wins only if its head and frame go into stock, its belly and trim into a staff meal or rillettes, and a cook's time is available to fillet it; otherwise the fillet is the cheaper and safer choice.

Running a yield test: weigh the item as delivered; break it down exactly as in service (fillet, portion, trim); weigh portions, usable by-products and waste separately; calculate yield = EP ÷ AP and cost per edible kg; repeat with three deliveries and take the average; record it on the standard recipe (XXXI.3). Retest when the supplier, the size or the season changes — the yield of a spring chicken is not that of a winter one.

At the stove

Weigh a head of broccoli, cut it into florets for a dish, weigh the florets and the stalks, and calculate its yield. Then cook the stalks too.

Whole-animal butchery and "nose-to-tail" cooking, championed by restaurants such as London's St. John from 1994, revived the use of offal and trim in Western restaurants; it was always the norm in Chinese, French provincial and most traditional kitchens.

Terms

AP (as purchased)
The weight bought, including inedible parts.
EP (edible portion)
The weight that can be served.
Yield
EP ÷ AP, as a percentage.
Yield test
Breaking down and weighing a product to measure its yield.
Yield = EP ÷ AP. Order AP = EP ÷ yield; the real cost is AP price ÷ yield (plus labour). Whole products pay only if their by-products are used. Measure your own yields with a yield test.

Sources

  1. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.