Here is an example of food calories from www.scientificamerican.com.
As the article says : "The method of using a combustion calorimeter to measure food calories is not frequently used today. However, after some considerations it can, and is, used today for checking the production quality of food."
Let's look at the details :
An estimate of the major nutritional components look like :
Of course there are differences between the above components. For details check the National Data Lab Website.
If one substitutes carbohydrates with protein then the measured calorific value will stay the same. However, if the fat (oil) content changes then the CV will change drastically. Therefore, the combustion calorimeter can be used to measure the change in fat, oil, and alcohol content.
It is a valuable tool in assuring the fat content in feed/food stuff. Good examples are : potato chips, fish in oil, sauce powder, etc. Since we are concerned with our daily calorie intake, the fat is the most damaging component, the calorimeter becomes a valuable tool in checking on the fat content.
This leaves the fibres as the major interfering food component : It burns well in the calorimeter, but has very little or no nutritional value. In a calorimeter it produces :
The CAL3K is equipped to reduce the calorific value when the fibre content is entered as a percentage of the mass. The fibre content of the measuring sample can be added together from the individual food components. But a little warning : If you reduce the protein and increase the fibre content then the calorimeter would not detect this. But you may taste it.
The calorimeter is a valuable tool to measure food calories if one keeps the fibre content stable. It is primarily used for quality control and because it is a very fast method.
The water (moisture) content does not produce any calorific value in a body or in the calorimeter. It must be considered if a dried sample is burned. This applies to cold drinks and other liquids. They are reduced to a syrup by boiling them until most of the water is evaporated. However, the syrup has a moisture content, it is not completely dry. This moisture content can be entered in the CAL3K Calorimeter and the calorimeter will calculate the dry CV. If a liquid is reduced to crystals (dry!) then the moisture compensation can be ignored.
RELATED APPLICATION NOTES
Many institutions are doing research and development on food. The aim is to improve the nutritional value of the food. The parameters may be to compare different foods or different manufacturers or to genetically improve the food. Other aspects may be to improve the digestion and energy absorption of animal feeds. Part of the research involves determining the calorific value of the food. The calorific value of a particular food is the same as the energy content of that food. The food can be for either human consumption or animal consumption