Recipe Calculation - Adjustment of moisture content |
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| | Updated 2019-11-27 |
| Using simple recipe calculation to adjust the nutrient values of foods based on the moisture content |
One of the most important components in food composition work is
moisture. The moisture content of many foods, especially foods with
a high moisture content like fruits and vegetables, can vary
significantly. This is one of the reasons why components like trace
elements in some environments often are expressed on a dry weight
basis. Even small differences in moisture content can lead to large
differences in dry matter content.
Adjustment of moisture content is one of the simplest recipe
calculation procedures. It only includes changes in moisture content
with corresponding adjustment of all other compositional values. The
simple adjustment does not include any form of retention factors.
The procedure is most often used in order to eliminate
unnecessary bias in precision aggregation of food data from
different sources - very often by converting all values to dry
weight basis, aggregating the data and then convert values back to
the common wet weight basis, e.g. per 100 g edible food.
When nutrient values of foods of different origin are compared or
aggregated, and nutrient contents are expressed in units of amounts
per fresh weight, e.g. per 100 g edible portion, it is important
first to adjust the nutrient contents of one or both compared foods
to the values they would have if they had the same moisture content.
Moisture adjustments are especially important for foods with a high
moisture content, typically fresh fruits and vegetables.
Failure to adjust for moisture differences adds unnecessary variability (“noise”) to the nutrient content of an aggregated food based on nutrient values from different sources.
The traditional procedure of adjustment of compositional values
according to a specific moisture content is described in detail in
"classic" food composition tables like the Food Composition
table for Use in Africa
and in Food Composition. Tables for Use in the Middle East.
The use of a nomogram for calculation of a conversion factor is
described in detail.
The original procedure is described by Claude Jardin in 1968. The specific procedure
can be found in Food Composition
table for Use in Africa (Annex II, page 227
).
- Jardin, C.:
Composition des aliments et pourcentage d'humidité.
Ann. Nutr. Alim., Vol. 22, pp. 329-333, 1968.
- Pellet, P. L. ; Shadarevian, S.:
Food composition. Tables for Use in the Middle East.
Faculty of Agricultural Science, American University of Beirut, Lebanon,
1970.
- U.S. Department of Health, Education, and Welfare and
Food and Agriculture Organization of the United Nations:
Food Composition Table for Use in Africa.
U.S. Department of Health, Education and Welfare, Bethesda, USA,
1968
- Polacchi, W.:
Food composition tables: Recommended method for deriving
nutrient values in their preparation.
Journal of The American Dietetic Association, Volume 85 Number
9, September 1985.
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