prep-yield

---
name: prep-yield
description: Measures what one delivered box actually turns into once it has been prepped, calculates the real cost per saleable portion rather than the invoice cost, works the usable trim through the waste hierarchy in order, and checks each proposed reuse against the temperature, time and allergen rules before it reaches a menu. Use when a dish costs more than it should, when a supplier wants to change a pack or a cut, or when you suspect the bin is eating a portion out of every box.
---

# The real cost of a portion, and the portion you were throwing away

You give this one ingredient, one delivery, one prep session and a set of scales. You get back a dated yield record: what the box weighed in, what it weighed as saleable product, what came off as usable trim and what as genuine waste, the true cost per saleable kilo against the invoice cost, a ranked list of what the trim could become worked through the statutory waste hierarchy in order, and a safety and allergen check on each idea before anyone writes it on a board. It will not tell you a normal yield for your ingredient, because that depends on your supplier, your cut and your knife, and a borrowed figure is how a kitchen convinces itself it is fine.

## What it does

1. **Weigh the box before anything is opened, and record what it was supposed to be.** Take the gross weight, the net weight after packaging, the supplier, the pack specification as ordered, the delivery date and the invoice unit cost. A yield is a ratio and half of it is the delivery. This is also where a short delivery becomes visible: a box specified at ten kilograms that weighs nine and a half is a credit note, not a yield problem, and the two are confused constantly because both surface later as a dish that costs too much.

2. **Prep it once, properly, and weigh every stream that leaves the board.** Four containers: saleable product, usable trim, inedible parts, and genuine waste. Weigh each as it accumulates rather than at the end. The distinction between usable trim and inedible is the whole exercise, and it is a judgement a chef makes with a knife in hand rather than one a document can assign. WRAP's Guardians of Grub puts all of it in one bucket for counting purposes, defining preparation waste as "Food that is thrown away during preparation, such as offcuts, and food that is served but not saved", which is right for a weekly count and too coarse for this job. Here the offcuts get split.

3. **Work out the yield percentage and the true cost per saleable kilo, then put both next to the invoice price.** Yield is saleable weight divided by delivered net weight. True cost per saleable kilo is the invoice cost of the whole box divided by the saleable weight. A box at eight pounds a kilo that yields seventy per cent is a twelve pound ingredient on the plate, and the gap between those two numbers is what the dish costing has been missing. Show both figures with the weights they came from, because a costing that cannot be traced back to a scale reading gets argued with and then ignored.

4. **Take the trim through the hierarchy in the order the law sets, rather than straight to stock.** Regulation 12 of the Waste (England and Wales) Regulations 2011 requires an establishment to apply "the following waste hierarchy as a priority order", being "(a) prevention; (b) preparing for re-use; (c) recycling; (d) other recovery (for example energy recovery); (e) disposal". GOV.UK's food and drink version expands the top into eight options and is clear about which part is which: "Options 1 to 4 offer you guidance on how to prevent food waste occurring in your business. Options 5 to 8 are required by law." So the first question is never what to make with the trim. It is whether the trim needed to exist: a different cut, a different pack, a different specification. Guardians of Grub gives the worked example for carcasses, which is to consider "using bones in stocks, or if you don't use stock you could talk to your meat supplier about supplying meat off the bone".

5. **Check every proposed reuse against the cooking and holding rules before it becomes an idea.** GOV.UK's food hygiene guidance for businesses sets the numbers: "Standard advice is to cook food until it has reached a core temperature of 70°C for 2 minutes", with equivalents including "75°C for 30 seconds" and "80°C for 6 seconds". Hot food "must be kept at or above 63°C if you're not serving it straight away", and "You can keep it below 63°C for up to 2 hours. After that, cool it as quickly as possible to 8°C or below, or throw it away." Reheating is the hard limit: "Reheating means cooking food again, not just warming it up. Reheat food until it is steaming hot all the way through. You can only reheat food once." A stock made from yesterday's bones and reheated to order twice is not a yield gain, it is a food safety failure with a costing attached.

6. **Check the chill and the clock for anything held rather than used the same day.** Chilled food "must be kept at 8°C or below. This is a legal requirement in England, Wales and Northern Ireland", and the guidance recommends setting the fridge to 5°C or below to absorb fluctuation. Out of the fridge, "You can keep chilled food out of the fridge for up to 4 hours, then you must throw it away. If it's been out for less than 4 hours, it can be put back in the fridge." For anything cooked to extend its life, the date label guidance is specific: food cooked before its use-by date must then be cooled and kept in the fridge, and "You must then eat it within 48 hours or freeze it to eat at a later date", with defrosted food to be used "within 24 hours". Every trim idea gets a written hold time, not an assumption.

7. **Change the specification rather than asking the kitchen to work harder.** A yield gained by careful knife work on a Tuesday disappears on a Saturday. A yield gained by ordering a different cut, a different grade or a different pack size survives, because it does not depend on who is on the board. So the options are ranked by permanence: change what you buy, then change the dish so the trim is part of it, then change the process, and only then ask for more careful prep. Put the question to the supplier in writing with the weights attached, because a supplier shown a measured yield on their own product responds differently to one shown an opinion.

8. **Treat a dish built from trim as a new dish for allergen purposes, because it is one.** FSA guidance for food businesses states that where you provide non-prepacked food "you must supply allergen information for every item that contains any of the 14 allergens", that this applies to "meals served in a restaurant, and food from a takeaway", and that businesses "must make sure that staff receive training on allergens". Its advice on how to give it is that "written allergen information, supported by a conversation, works best for consumers". A stock enriched with an offcut, a sauce thickened with a trimmed crust, a garnish made from a peel: each changes the allergen record of every dish it touches, and the record is a written one that has to be updated before service, not after a question at the pass.

9. **Re-weigh the same ingredient after the change, and date both records.** One yield reading is a number, two are a measurement. Repeat with the same scales, the same four containers and the same person where possible, and record the delivery date and supplier both times, because a yield change that coincides with a new supplier is not evidence that the specification worked. Keep both records with the build date on the front, and note beside the result which parts came from a scale and which from a judgement. This is a costing and prep exercise, not a compliance document, and the file should say so.

## Then it checks

1. The delivered net weight and the invoice unit cost are both recorded from the delivery and the invoice, not from the order, and any shortfall against the pack specification is named as a delivery issue rather than absorbed into the yield.
2. The four streams weigh, within a stated tolerance, to the delivered net weight, and any difference is named rather than distributed silently across the streams.
3. The yield percentage and the true cost per saleable kilo are both shown with the two weights each was calculated from.
4. Every proposed reuse carries a cooking or reheating step with a temperature and a time, a hold temperature, and a written hold time, and nothing is proposed that requires reheating more than once.
5. Every proposed reuse names the allergens it introduces into each dish it touches, and says where the written allergen record for those dishes will be updated and by whom.
6. The options are ranked with specification and purchasing changes above process changes, nothing states a normal or typical yield for the ingredient, and every rule quoted names its source and the date that source was read.

Any check fails: name it, redo that step once. Failed twice: say what is wrong and stop.

## Rules
- Public information only.
- Never invent a fact, a number or a quote.
- Anything sent in someone's name says whose name it is. A yield report sent to a supplier goes out over the name of the person who will take the call.
- Never state a typical, standard or industry yield for an ingredient, a cut or a pack. Yield depends on the supplier, the specification, the season and the knife, and a borrowed percentage either flatters a bad supplier or condemns a good one.
- Never propose a reuse that cannot be given a temperature, a time and a hold limit. "Use it up in a staff meal" is not a method, and staff are customers for the purposes of every rule in step 5 and step 6.
- Never propose reheating anything twice, holding cooked food below 63 degrees for more than two hours, or returning food to the fridge after four hours out of it. Refuse these even where a chef says it is normal practice, and say which guidance forbids it.
- Never write a new dish onto a menu, a board or a specials list from this file. The file proposes; the chef decides; the allergen record is updated before anything is sold.
- Never treat a yield improvement as a cash saving in the accounts. It is a lower cost per portion, and it becomes cash only if the purchasing changes, which is a separate decision with a separate date.
- This output is a working document prepared for the owner and head chef to check against their own recipes, suppliers and food safety management system, and for their environmental health officer to see if asked. It applies published food safety and allergen guidance to proposed changes. It is not food safety advice, it is not a hazard analysis, and it does not replace the venue's own Safer Food Better Business pack or equivalent.

## Built from
- The Waste (England and Wales) Regulations 2011, SI 2011/988, regulation 12, https://www.legislation.gov.uk/uksi/2011/988/regulation/12/made, read 16 September 2026: the five step priority order that step 4 forces the trim options through, quoted in full.
- GOV.UK, Department for Environment, Food and Rural Affairs, "Food and drink waste hierarchy: deal with surplus and waste", https://www.gov.uk/government/publications/food-and-drink-waste-hierarchy-deal-with-surplus-and-waste/food-and-drink-waste-hierarchy-deal-with-surplus-and-waste, updated 1 January 2024, read 16 September 2026: the split between the four guidance options and the four legal ones in step 4, which is why prevention is asked about before reuse.
- GOV.UK, "Food hygiene for businesses: Cooking food safely", https://www.gov.uk/food-hygiene-businesses/cooking, no publication date shown on the page, read 16 September 2026: the 70°C for 2 minutes core temperature and its equivalents, the 63°C hot holding rule with the two hour limit, and the single reheat rule, all in step 5.
- GOV.UK, "Food hygiene for businesses: Chilling and freezing", https://www.gov.uk/food-hygiene-businesses/chilling-and-freezing, no publication date shown on the page, read 16 September 2026: the 8°C legal requirement, the 5°C fridge setting recommendation and the four hour rule in step 6.
- GOV.UK, "Understanding food labelling: Best before and use-by dates", https://www.gov.uk/understanding-food-labelling/best-before-and-use-by-dates, no publication date shown on the page, read 16 September 2026: the 48 hour limit after cooking and the 24 hour limit after defrosting in step 6.
- Food Standards Agency, "Allergen guidance for food businesses", https://www.gov.uk/government/publications/allergen-guidance-for-food-businesses/allergen-guidance-for-food-businesses, updated 17 July 2026, read 16 September 2026: the duty to supply allergen information for every non-prepacked item containing any of the 14 allergens, the application to restaurant and takeaway meals, the staff training requirement and the written information advice, all in step 8.
- WRAP, "Frequently Asked Questions for the Hospitality and Food Service sector", Guardians of Grub, https://guardiansofgrub.com/faqs/, no publication date shown on the page, copyright notice reads "WRAP 2024", read 16 September 2026: the definition of preparation waste that step 2 deliberately splits further, and the carcass example in step 4.

This is a working document prepared for the owner and head chef to check against their own recipes, suppliers and food safety management system before it is relied on. It is not food safety advice and it does not replace the venue's own food safety management system.

# prep-yield

## You are given
One prep session's raw weighing sheet for one ingredient at one hospitality site. It holds the supplier, the pack specification as ordered, the delivery date, the invoice reference and unit cost, the gross and net delivered weights, and a weight in kilograms for each stream leaving the board, each already assigned by the chef to `saleable`, `usable trim`, `inedible`, or `waste`. Alongside it: the dishes the saleable product goes into, with their current recipe costings and written allergen records; a list of proposed uses for the usable trim, each written by the chef with the cooking method, the holding method and the intended hold time in the chef's own words; the statutory waste hierarchy priority order and the food safety and allergen wording Claude relied on, each with its source URL and the date it was read; Claude's classification of each proposed use into a hierarchy step; and, where a second session has been run after a change, the same sheet again with its own date. Missing values arrive as the word `not supplied`.

## Produce
Write into a `./prep-yield-output/` folder:

1. `delivery.csv` with these columns in this order: `ingredient`, `supplier`, `pack_specification_as_ordered`, `delivery_date`, `invoice_reference`, `invoice_unit_cost_gbp_per_kg`, `gross_weight_kg`, `packaging_weight_kg`, `net_delivered_kg`, `specification_weight_kg`, `shortfall_kg`, `shortfall_is_a_delivery_issue`. One row per prep session. `shortfall_kg` is `specification_weight_kg` minus `net_delivered_kg`, computed. `shortfall_is_a_delivery_issue` is `yes` where `shortfall_kg` is greater than zero.
2. `streams.csv` with columns: `session_date`, `stream`, `weight_kg`, `share_of_net_delivered`, `container`, `tare_kg`, `weight_basis`, `chef_note_verbatim`. `stream` is exactly one of `saleable`, `usable trim`, `inedible`, `waste`, copied from the input and never reassigned. `weight_basis` is `weighed` or `estimated by kitchen`. A `RECONCILIATION` row gives the sum of the four streams, the `net_delivered_kg`, and the difference.
3. `yield.csv` with columns: `session_date`, `ingredient`, `net_delivered_kg`, `saleable_kg`, `yield_percent`, `invoice_cost_of_box_gbp`, `invoice_cost_per_kg_gbp`, `true_cost_per_saleable_kg_gbp`, `uplift_gbp_per_kg`, `uplift_percent`. All computed, none copied. `yield_percent` is `saleable_kg` divided by `net_delivered_kg`.
4. `dish-recosting.csv` with columns: `dish`, `portion_weight_of_this_ingredient_kg`, `cost_in_current_costing_gbp`, `cost_at_true_yield_gbp`, `difference_gbp`, `current_costing_source`, `current_costing_date`. Only dishes supplied in the input appear. No menu price, no gross profit percentage and no suggested price appears in any column.
5. `trim-options.csv` with columns: `option_ref`, `proposed_use_verbatim`, `hierarchy_step`, `permanence_rank`, `cooking_step_verbatim`, `core_temperature_and_time`, `hold_temperature`, `hold_time`, `reheats_required`, `safety_verdict`, `rule_cited`. `hierarchy_step` is exactly one of `prevention`, `preparing for re-use`, `recycling`, `other recovery`, `disposal`, copied from the input. `permanence_rank` is exactly one of `change what you buy`, `change the dish`, `change the process`, `rely on more careful prep`. `safety_verdict` is exactly one of `temperatures and times supplied`, `no temperature supplied`, `no hold time supplied`, `requires more than one reheat`, `exceeds two hours below 63C`, `exceeds four hours out of chill`, `exceeds 48 hours after cooking`, `exceeds 24 hours after defrosting`. Every verdict other than the first carries a non-empty `rule_cited` and is listed in `gaps.md`.
6. `allergen-impact.csv` with columns: `option_ref`, `dish_affected`, `allergens_introduced`, `allergens_already_declared`, `record_needs_updating`, `where_the_record_is_held`, `who_updates_it`, `updated_before_service`. `allergens_introduced` lists only names from the 14 supplied in the input. `record_needs_updating` and `updated_before_service` are `yes`, `no` or `not supplied`.
7. `yield-record.md` - the dated record in plain sentences: the ingredient, supplier and specification, the four stream weights, the yield percentage, the invoice cost per kilogram against the true cost per saleable kilogram, the reconciliation difference, the trim options in permanence order with their safety verdicts, and where a second session exists, both sessions side by side with their dates and suppliers. No typical yield, no target yield, no comparison to any other ingredient, site or supplier.
8. `gaps.md` - a numbered list of: any stream with `weight_basis` of `estimated by kitchen`; any reconciliation difference greater than the stated tolerance; any delivery shortfall against specification; any trim option with a `safety_verdict` other than `temperatures and times supplied`, naming the rule; any trim option whose allergen impact is `not supplied`; any dish whose current costing has no source or date; and any missing source URL or read date.

## Rules
- Codex measures, computes, reconciles and checks. It never invents, never reassigns a stream or a hierarchy step supplied by the chef, never rewords a proposed use, and never decides whether a trim idea is a good one.
- Never write a typical, standard, industry or target yield for any ingredient, cut or pack. No such figure appears in any file.
- Never write a menu price, a selling price, a gross profit percentage or a suggested price anywhere. This file costs portions, it does not price them.
- Never write `temperatures and times supplied` where any of the core temperature, the time, the hold temperature or the hold time is missing. A partial set is a gap, not a pass.
- Never propose a use, a temperature, a time or a substitution that was not supplied. Where a chef's note lacks a temperature, the cell is empty and the row is flagged; it is never filled with a standard figure.
- Never record a trim option as safe. `safety_verdict` describes what was supplied against the quoted rules and nothing else, and no file states that a dish is safe or that the site complies with food safety law.
- Reconcile before reporting: the four stream weights are summed and compared to `net_delivered_kg`, and the difference is shown rather than spread across the streams.
- Never convert a yield improvement into an annual saving, a cash figure for the accounts, or a percentage off food cost.
- Use British English, GBP for money, kilograms to three decimal places for stream weights, degrees Celsius written as for example `70C` in CSV cells, and DD Month YYYY for every date. No em dashes in any file you write, and any supplied text containing one is recorded verbatim and flagged in `gaps.md`.
- Every file ends with this line: this is a working document prepared for the owner and head chef to check against their own recipes, suppliers and food safety management system before it is relied on; it is not food safety advice.

## Return
The absolute path of each file written, the row count of each CSV, the ingredient, supplier and delivery date, the four stream weights and the reconciliation difference against the delivered net weight, the yield percentage, the invoice cost per kilogram and the true cost per saleable kilogram with the uplift between them, the number of dishes recosted and the largest single difference with the dish named, the number of trim options by `permanence_rank`, every trim option whose `safety_verdict` was not `temperatures and times supplied` with the rule cited for each, the number of dishes whose allergen record needs updating and whether an updater was named for each, whether a second session was supplied and the change in yield between the two if so, and the `gaps.md` item count.