Hello:
The hard part of determining the density of foods is getting an accurate measure of the volume. Foe liquids, it’s fairly straightforward. You take a graduated
cylinder and weigh it with and without the liquid and you can read the volume off the markings. This will also work with dry powders and foods composed of small particles. However, the final measurement of the density will be affected by the degree of compaction.
This is why we see recipes in the US call for sifted flour, as we use cups rather than weighing out the flour.
However trying to determine the volume of an irregularly shaped piece of food, say a piece of broccoli or a loaf of bread, is much harder. Archimede’s principle
figures out volume by displacement, but you can’t use water if the material you’re measuring will absorb the water, so you have to use a dry substance, such as very small seeds. The baking industry traditionally used canola seeds, but any very small seed
will do. You determine the volume of the seeds, then add the food you’re measuring being sure to completely cover it, then measure the volume again.
Hope this is helpful.
David B. Haytowitz
Nutritionist
USDA, Agricultural Research Service
Nutrient Data Laboratory
Room 207A, Building 005, BARC-West
10300 Baltimore Avenue
Beltsville, MD 20705
301.504.0714 (voice)
301.504.0632 (fax)
From: Food Composition Discussion Group [mailto:[log in to unmask]]
On Behalf Of Charrondiere, Ruth (ESN)
Sent: Monday, May 11, 2015 10:43 AM
To: [log in to unmask]
Subject: Re: Best Practices for Calculating Density Conversion Factors
Dear Jessica,
you take a laboratory scale, put an empty glass or other container on it, weigh it. Then fill it up with water coming from the fridge. weigh it. Record the difference
in weight which is your volume. Then weigh all foods in this container and divide it by the volume. Describe the food well, e.g. fish powder, loose; raw eggplant without skin in 1 cm cubes. Record your location (altitude). I would be happy to include your
data in our next version of the FAO/INFOODS density database
Best wishes
Ruth
P.S. Anyone else willing to contribute data are most welcome
From: Food Composition Discussion Group [[log in to unmask]]
On Behalf Of Raneri, Jessica (Bioversity) [[log in to unmask]]
Sent: Monday, May 11, 2015 2:12 PM
To: [log in to unmask]
Subject: Best Practices for Calculating Density Conversion Factors
Dear Infoods Members,
We’re currently attempting to identify the density conversion factors of some unique foods in Vietnam in order to analyse 24hr recall data. Is anyone aware of guidelines
or best-practices manual on how to calculate these densities? We would like to eventually make the data publically available.
Many thanks in advance.
Jessica Raneri, MSc
Nutritionist, Research Support Officer
Nutrition and Marketing Diversity Programme,
Bioversity International
Via dei Tre Denari, 472/a
00057 Maccarese (Fiumicino)
Rome, Italy
P Please
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