Describe how to find calorie content in food

To find the calorie content in food:

Importantly, a calorie will not be considered as full or empty and not a thing too.  You cannot tie calories in a bottle. A calorie is a unit of measure of energy. We can also say that, it is the energy amount that is needed to rise the temperature of one ml of water by 1 degree Celsius.

Earlier, a calorimeter was used to measure the calorie content of food. That is, a certain amount of food in which water content has evaporated, and this food was put in a vessel surrounded by some water. The container was then sealed, oxygen was supplied in, and the food was ignited.

From the temperature increase of water, the calorie content of food was determined. Today, producers use the “At water indirect system” to find calorie content by adding the calories containing the energy nutrients: protein, carbohydrate, fat and alcohol.

The At water system makes use of the average values of 4 K cal/g for protein, 4 K cal/g for carbohydrate, 9 K cal/g for fat and  7 K cal/g for alcohol that were determined by burning these substances in a calorimeter.

Thus the label on a 45 gram Perk that contains 3 g of protein, 29 g of carbohydrate (22 grams of which are simple sugars) and 12 g of fat would read 230 Calories.

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)