Thanks Barbara,
what you say is and was rather clear.
My question raised since I was not sure about the orginial goals, from a doubt:
in case we have to tackle with lesser explored foods of which we want to calculate energy, why not to start using weight, so that derive rather exact values.
Then converting to a volume is possible at any time, having the correct references and if really needed.
.
Filippo D'Antuono
Professore ordinario, Colture alimentari, qualità e produzione
Full professor, Food crops production and quality
Dipartimento di scienze e tecnologie agroalimentari
Campus Unversitario di Scienza degli alimenti
Department of Agri-food science and technology
Food Science University Campus
Università di Bologna / University of Bologna
Piazza Goidanich 60
47521 Cesena Italia
e-mail: [log in to unmask]
<mailto:[log in to unmask]>
Tel +39 0547 338126
Fax+ +39 0547 382348
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Da: Food Composition Discussion Group [[log in to unmask]] per conto di Barbara Selley [[log in to unmask]]
Inviato: mercoledì 13 maggio 2015 3.30
A: [log in to unmask]
Oggetto: Re: Best Practices for Calculating Density Conversion Factors
Hello all,
I value this listserv for many reasons, not least of which being that it brings analysts, databases compilers and users together to better understand the viewpoints of one another and the issues that concern them.
Jessica’s original question highlights the importance of including volume-to-weight (and count-to-weight) conversion factors in databases and other publications—not very important to the chemist but essential for the end user.
To answer Professor D’Antuono’s question “why not go to directly to weight?”
Food recalls and records often report food quantities by volume, and the same is true for recipe ingredient listings (especially in North America). It would be much easier if all were recorded by weight but this isn’t going to happen in the real world. Hence, the need for volume to weight conversion factors.
To avoid confusion conversion factor names need to be detailed.
The following examples are derived from USDA SR27.
NDB # 01005
Cheese, brick. Wt g
100 mL diced 56
100 mL shredded 48
100 cc solid 104
Food quantities may also be expressed as counts, e.g. 3 carrots, for which default conversion factors are also required.
NDB# 11124
Carrots, raw Wt g
100 mL chopped 54
100 mL grated 46
100 mL strips or slices 52
1 large (19-22 cm) 72
1 medium* 61
1 small (14 cm) 50
*or size not specified
I’d like to suggest the terms “volume-to-weight” and “count-to-weight” conversion factors. Their purpose is clearly stated, so they are less likely to cause confusion than “density conversion factor.”
A further related point: when analyzing recipes for which nutrients per unit of weight will be added to a database, both the tested finished weight and volume should be recorded. The volume-to-weight conversion derived from this information will permit the user to enter volume quantities.
Kind regards,
Barbara Selley, RD
Food Intelligence
[log in to unmask]
416 962 2884
From: Food Composition Discussion Group [mailto:[log in to unmask]] On Behalf Of Anders Møller
Sent: Monday, May 11, 2015 2:34 PM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: Re: Best Practices for Calculating Density Conversion Factors
Yes, David!
That is what I missed – the particles size is an important measure to consider – and report.
Thanks,
Anders
From: Food Composition Discussion Group [mailto:[log in to unmask]] On Behalf Of Haytowitz, David
Sent: 11 May 2015 19:47
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: Re: Best Practices for Calculating Density Conversion Factors
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)
[log in to unmask]<mailto:[log in to unmask]>
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]<mailto:[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]<mailto:[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<http://www.bioversityinternational.org/>
Via dei Tre Denari, 472/a
00057 Maccarese (Fiumicino)
Rome, Italy
P Please consider the environment before printing this e-mail
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