Keep dry and prepared nutrition values on separate tracks

Dry and prepared weights describe different states of a food. Adding water can increase weight substantially, so a nutrient amount per 100 g of dry mix cannot be compared directly with a value per 100 g of the prepared dish.

Article 31 of the EU food information regulation addresses food as sold and, where appropriate, after preparation with specified instructions. Read the panel heading and preparation directions together before choosing your calculation.

Use a complete yield example

Imagine a fictional dry mix contains 8 g protein per 100 g. You use 50 g of mix, add water, and obtain a final prepared weight of 200 g. Assume for this arithmetic exercise that all the mix remains in the dish and water is the only addition.

The dry mix contributes 8 × 50 ÷ 100 = 4 g protein to the whole prepared batch. Dividing that total by the 200 g prepared yield gives 4 ÷ 200 × 100 = 2 g protein per 100 g prepared.

The values eight and two are compatible. They describe different amounts of the original mix within the same 100 g comparison weight. Neither number tells you that preparation destroyed three quarters of the protein.

List what the simple example leaves out

Milk, oil, sauces, and other additions can contribute their own nutrients. If the instructions include them, calculate their contributions separately or use a prepared-food declaration that matches the actual recipe. Substituting another ingredient makes the printed prepared column a different scenario.

Cooking losses, discarded liquid, and food left in a pan also complicate a simple mass balance. Do not assume that a dry-food total applies unchanged to a final dish when some ingredients were discarded. A measured final weight alone cannot reveal the nutrient content of what was lost.

Save a preparation record

• Copy whether the original panel describes dry, as-sold, or prepared food.
• Record the amount of dry product used.
• List additions and any discarded material.
• Measure the final yield only after the stated preparation step.

For your portion, multiply the batch total by the portion's share of the finished weight, assuming a reasonably even mixture. Keep the dry input and prepared output as separate records so future comparisons do not silently switch between them.