1, direct measurement method: it is to burn food with a special device and measure the heat released. This method is the most direct, but it is very troublesome and will hardly be used in actual production.

2. Calculation method for determining ingredients: In most foods, calories come from protein, fat and carbohydrates. These three food ingredients have an average calorie value. protein and carbohydrate are 4 kcal/g, and fat is 9 kcal/g. Dietary fiber in carbohydrate is more complicated. Generally, soluble dietary fiber is calculated at 2 kcal/g, while insoluble dietary fiber is not counted as calories.

As long as the content of these components is measured, the heat can be calculated. However, carbohydrates cannot be measured directly, but other components such as water, ash, protein and fat are measured, and the remaining "other components" are subtracted from the total amount as carbohydrate content.

3. Calculation method according to formula: In food production, it is calculated according to formula in most cases. The formula of a product is certain, and the nutrients of the raw materials used are relatively constant. According to the formula, we can also calculate the contents of various nutrients, and then according to their respective calorie values, we can calculate the calories of this food.

Extended data

Daily calorie requirement

1, the daily calories required by adults = the basic calories required for basic metabolism of human body+the calories required for physical activity+the calories required for digesting food.

2. Calories required for digesting food = 10% x (minimum calories required for basic metabolism of human body+calories required for physical activity).

3. Adults' daily calories = 1. 1 x (minimum basic calories required for basic metabolism of human body+calories required for physical activity).

Male: 9250- 10090KJ

Female: 7980-8820 kJ?

Baidu encyclopedia-food calories