Cooking changes the nutritional content of a foodstuff. The degree of change depends on factors such as the nature of the foodstuff, cooking technique, duration of cooking and cooking temperature. Different weight changes and modifications to the nutrient can occur, depending on the cooking technique.
The nutrient content of a cooked foodstuff or a composed dish can either be analysed or calculated. Analysis has the advantage that it delivers exact values. However, analyses are demanding, time-consuming and expensive. In practice, the nutrient content of a prepared product is therefore mostly calculated using average loss factors and absorption factors. This also the case for the Swiss Food Composition Database.
When calculating the nutrient content of a prepared foodstuff, possible weight changes in addition to the nutrient losses also have to be taken into account. A weight loss corresponds to a concentration. The vitamin and mineral contents per 100 g of a cooked foodstuff can therefore turn out to be higher than those of the corresponding raw products in spite of nutrient losses. Conversely, a weight gain (e.g. when cooking pasta) corresponds to a dilution and the nutrient content per 100 g of the cooked foodstuff is significantly lower than that of the uncooked, dry foodstuff.