Determining Total and Soluble Protein with the FP828

Hen (scientific name Gallus gallus domesticus) outside her coop on a farm98% of the world's soybean meal is used as animal feed, principally as a protein supplement. With the importance of protein in animal growth and development, knowing what's in your soybean meal is vitally important. There is more to protein than the crude protein concentration number, however. If an animal can't digest the protein, if it isn't a 'soluble' protein, then it doesn't actually provide the nutritional value needed. LECO's FP828 is capable of both total and soluble protein analyses.

Amino acids attach to each other in long polypeptide chains to create proteins. As the proteins move through the digestive system, acids and enzymes break down these chains until they can be absorbed by the small intestine. Proteins that can be broken down in this way are considered soluble proteins.

Not every protein in soybean meal is soluble. Under- or over-processed soybean meal can contain enzyme inhibitors or have damage to the protein structures, preventing full digestion and reducing the nutritional value of the meal.


Typically, soybean meal is approximately 40% to 50% protein. The amount of protein in the soybean meal helps characterize it and determines the quality of the meal or flour. The FP828 can evaluate the crude protein concentration in a sample by measuring the nitrogen in a sample and applying a protein factor or multiplier.

Sample analysis can be taken a step further with a second analysis. By splitting the original sample in two, half can be used to determine the crude protein content, while the other half can undergo chemical treatment, such as KOH digestion, before having the nitrogen measured and the protein factor or multiplier applied. With knowledge of the crude protein percentage and the soluble protein percentage, the percent of soluble protein of the total protein can be calculated and used to determine the quality of the soybean meal processing.

Learn more by reading two Application Notes showing how easily the FP828 can determine protein in soybean meal, both total protein content and soluble protein content.

Total Protein Application Note Soluble Protein Application Note