Google Answers Logo
View Question
Q: How to test percentage of crude protein? ( No Answer,   2 Comments )
Subject: How to test percentage of crude protein?
Category: Science > Agriculture and Farming
Asked by: josephltt-ga
List Price: $10.00
Posted: 18 Oct 2005 05:08 PDT
Expires: 17 Nov 2005 04:08 PST
Question ID: 581622
Hi, I wish to know is there anyway to test percentage of protein in
anything fast and accurate without sending them to the laboratory. Is
there portable and cheap kit that can do the job?

Clarification of Question by josephltt-ga on 21 Oct 2005 18:34 PDT
The material that I wish to test is some food material. Eg, Wheat, Soy
meal, feeds etc.
There is no answer at this time.

Subject: Re: How to test percentage of crude protein?
From: hfshaw-ga on 21 Oct 2005 14:35 PDT
It would help to know the nature of the material you want to test.  Is
it a solution?  Solid?  Suspension  (e.g., blood)?  What's the nature
of the non-protein material in the sample?
Subject: Re: How to test percentage of crude protein?
From: ike9898-ga on 22 Nov 2005 11:33 PST
Crude protein is normally determined by measuring the amount of
nitrogen in a sample and then using a conversion factor to estimate
how much protein that represents.  The classic mehtod is the Kjeldahl
Nitrogen assay.  This method is well documented and known by many food
chemists. It is relatively slow and labor intensive.  If you can make
a much bigger investment, there are automated systems that determine
the concentration of nitrogen.  We use one from Leco Corp.  Both these
methods would be laboratory based and not particularly cheap if you
don't already have the equipment.

As far as something cheap and portable, I think you're going to have a
hard time.  If you can be sure that all your protein is soluble, you
can use one of many commercially available kits for soluble protein
concentration.  Most of these depend on the use of a spectrophotometer
or a fluorimeter.  It might be possible to use something like the
Bicinchoninic Acid Assay, and visually compare the color of the
solution to a standardized color chart.  This would only give you a
very rough idea of protein concentration.

Important Disclaimer: Answers and comments provided on Google Answers are general information, and are not intended to substitute for informed professional medical, psychiatric, psychological, tax, legal, investment, accounting, or other professional advice. Google does not endorse, and expressly disclaims liability for any product, manufacturer, distributor, service or service provider mentioned or any opinion expressed in answers or comments. Please read carefully the Google Answers Terms of Service.

If you feel that you have found inappropriate content, please let us know by emailing us at with the question ID listed above. Thank you.
Search Google Answers for
Google Answers  

Google Home - Answers FAQ - Terms of Service - Privacy Policy