What is the energy value of products different from their nutritional value? Sometimes these two concepts combine in human consciousness.
Nutritional value - the content of protein, fats and carbohydrates in food per hundred grams of the product. Caloric content of products (energy value) - the amount of energy released in the human body from absorbed food in the process of digestion.
The caloric content of the product shows the amount of energy that a human body can obtain with the full assimilation of the product.
The actual amount of energy received depends on many factors. But in the first place it depends on the composition of a separate food product.
Principles of calculation of caloric content of products
The energy value (caloric value of products) is measured in kilojoules (kJ) or in kilocalories (in the European Union - kcal, in Russia - kcal, in the USA - calories) per hundred grams of the product. To measure the caloric content of foods, use nutritional calorie. The word "calorie" translates from Latin means "warm". One calorie contains the amount of heat needed to heat one gram of water per Kelvin (at a pressure of 101 325 Pascal).
By creating calorie tables of products in a modern way, in calories, the heat of combustion of fuel was measured. In European, Asian and American nutritionists, the caloric content of the same product is slightly different. The fact is that the chemical composition of vegetables, fruits and animals is determined by the conditions of their cultivation.
Any foods and foods contain calories. Some foods (dried dill, diet, black tea) contain a small amount of energy. Only water does not contain calories at all. Data on the content in a separate product of proteins, carbohydrates and fats, as well as about the caloric content of individual products can be found in the table of caloric content.
Calories are contained in proteins, fats and carbohydrates of food. Proteins carry out energy transformations and metabolism. The energy value of fats is about twice as high as carbohydrates. Fats in the human body break down into glycerol and fatty acids with energy release. Carbohydrates give the energy necessary for biochemical processes. With enough energy in the human body, free carbohydrates are converted into fuel stocks - fatty tissue (long-term supply) and glycogen (readily available stock). In the human body, free carbohydrates break down into fructose and glucose.
Fiber fiber (dietary fiber) has a lower energy value than sugar and starch. In many countries, fiber is not indicated on foods (caloric content is considered to be zero). In some countries (for example, in the US) fiber is considered one of the types of complex carbohydrates, the caloric content of fibers is about 4 kcal/g.
In calculating the caloric content of products, usually do not take into account such chemical components as pentosan, water, minerals, cellulose. Calculation shows the so-called theoretical caloric content of products, since conditionally accepted complete digestibility of human body fats, carbohydrates and protein foods.
In fact, food is absorbed by the body only partially. Thus, it is assumed that the average digestibility of fat is 94%, proteins - 84.5% and carbohydrates - 95.6%. To calculate the practical caloric content of finished products, it is necessary to consider their digestibility.
At the end of the 19th century, an American chemist Atvater developed a method for determining the nutritional energy based on the heat of combustion of a solid or liquid body in a calorimetric flask. To determine the caloric content, the selected food product is placed in a calorimetric flask, where it is burned, and then the heat is measured. Separately in the calorimeter's chamber, the heat measured by the tested person is measured. Further, the resulting amount is converted into "burned" calories in order to find out the physiological and real value of food.
This method for estimating the caloric content of food and energy (direct calorimetry method) has a number of disadvantages. The most serious is that the protein in the human body is oxidized in the same way as in a calorimeter, only in a state of depletion of the body.
Determination of caloric content of finished products
In order to correctly calculate the caloric content of the finished dishes, it is necessary to take into account the change in caloric content in different ways of their culinary processing. Correct calculation of caloric content of finished products will help to adjust the diet. The change in caloric content occurs due to the decomposition of fats, proteins and carbohydrates into the constituents when heated, as well as the fattening of fat from the food product and evaporation of it with water vapor.
In the process of cooking, a huge amount of minerals and vitamins is lost. When calculating the caloric content of products, you must always take into account the weight of the finished meal and the total amount of water used for cooking. So, to determine the caloric content of the finished meal, it is necessary to make the amount of energy in all the components needed for the preparation of this dish, and then divide the number received by the number of proportions.
To calculate calories in pasta and groats it is necessary to understand that the caloric content after cooking will be three-four times less than in raw form. After heat treatment, the mass of many products is significantly reduced. The loss of mass is mainly due to water loss. For example, beef cooking loses about 50% of water. The weight of potatoes during roasting is reduced by 30-60% (depending on the methods of frying and grinding). Drying berries, crackers or fruit reduces their volume several times. Therefore, the caloric content of finished products will be significantly higher than for culinary processing.
To correctly calculate the caloric content of dried products, it is necessary to find out how many times their weight decreased after drying, and then the table value indicated in the table of caloric content of the products multiplied by the resulting number.