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Traditionally, food companies would send food samples to laboratories for physical testing. Typical analyses include: moisture (water) by loss of mass at 102 °C; protein by analysis of total nitrogen, either by Dumas or Kjeldahl methods; total fat, traditionally by a solvent extraction, but often now by secondary methods such as NMR
The method consists of combusting a sample of known mass to a temperature between 800 and 900 °C in the presence of oxygen. This leads to the release of carbon dioxide, water and nitrogen. The gases are then passed over special columns (such as potassium hydroxide aqueous solution) that absorb the carbon dioxide and water.
Without modification, other forms of inorganic nitrogen, for instance nitrate, are not included in this measurement. Using an empirical relation between Kjeldahl nitrogen and protein, it is an important method for indirectly quantifying protein content of a sample. This method was developed by Johan Kjeldahl in 1883. [1] [2]
As foods vary by brands and stores, the figures should only be considered estimates, with more exact figures often included on product labels. For precise details about vitamins and mineral contents, the USDA source can be used. [1] To use the tables, click on "show" or "hide" at the far right for each food category.
Atmospheric nitrogen is less biologically available than dissolved nitrogen in the form of ammonia and nitrates. Availability of dissolved nitrogen may contribute to algal blooms . Ammonia and organic forms of nitrogen are often measured as Total Kjeldahl Nitrogen , and analysis for inorganic forms of nitrogen may be performed for more accurate ...
Food sampling is a process used to check that a food is safe and that it does not contain harmful contaminants, or that it contains only permitted additives at acceptable levels, or that it contains the right levels of key ingredients and its label declarations are correct, or to know the levels of nutrients present.
Biological value (BV) is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the organism's body. It captures how readily the digested protein can be used in protein synthesis in the cells of the organism. Proteins are the major source of nitrogen in food. BV assumes protein is the only ...
These reference values include water from drinking water, other beverages, and from food. About 80% of our daily water requirement comes from the beverages we drink, with the remaining 20% coming from food. [54] Water content varies depending on the type of food consumed, with fruit and vegetables containing more than cereals, for example. [55]