protein dispersibility index

{{Short description|Measure of protein solubility}}

The Protein Dispersibility Index (PDI) is a means of comparing the solubility of a protein in water, and is widely used in the soybean product industry.

A sample of the soybeans are ground, mixed with a specific quantity of water, and the two are then blended together at a specific rpm for a specific time. The resulting mixture and original bean flour then have their protein content measured using a combustion test, and the PDI is calculated as the percentage of the protein in the mix divided by the percentage in the flour - a PDI of 100 therefore indicates total solubility.{{cite web|url=http://www.ilcrop.com/ipglab/soybtest/soybdesc.htm|title=Illinois Crop Improvement Association Soybean Tests|accessdate=2007-06-26 |archiveurl = https://web.archive.org/web/20070813201738/http://www.ilcrop.com/ipglab/soybtest/soybdesc.htm |archivedate = 2007-08-13}}{{cite web|url=http://www.livestocktrail.uiuc.edu/sand/definitions.cfm|title=University of Illinois Extension - Soy in Animal Nutrition Databases|accessdate=2007-06-26|archive-url=https://web.archive.org/web/20070311215231/http://www.livestocktrail.uiuc.edu/sand/definitions.cfm|archive-date=2007-03-11|url-status=dead}}

It has been shown that the PDI can be affected, not only by the type of soybean used, but also by manufacturing processes - heat has been shown to lower the PDI.{{cite web |url=http://ps.fass.org/cgi/content/abstract/79/11/1592 |title=Protein dispersibility index as an indicator of adequately processed soybean meal |author1=AB Batal |author2=MW Douglas |author3=AE Engram |author4=CM Parsons |name-list-style=amp |accessdate=2007-06-26 |archive-date=2007-09-27 |archive-url=https://web.archive.org/web/20070927062559/http://ps.fass.org/cgi/content/abstract/79/11/1592 |url-status=dead }}

The PDI required of a soyflour is dependent on the purpose to which the soybeans are to be put. Manufacturers of soymilk and tofu products want a high PDI to ensure the maximum protein content in their products. However, manufacturers of soy-based fish feed require a low PDI to avoid loss of valuable protein into the surrounding water.{{cite journal |url=http://afs.allenpress.com/perlserv/?request=get-abstract&doi=10.1577%2F1548-8640(1984)46%3C161%3APDIPAA%3E2.0.CO%3B2 |title=Protein Dispersibility Index (PDI) As A Quality Control Measure For Soy Flour Used In Brown Trout Starter Feed |year=1984 |volume=46 |page=161 |doi=10.1577/1548-8640(1984)46<161:PDIPAA>2.0.CO;2 |issn=1548-8640 |accessdate=2007-06-26 |last1=Reinitz |first1=Gary |journal=The Progressive Fish-Culturist |issue=3 |url-access=subscription }}{{Dead link|date=December 2024 |bot=InternetArchiveBot |fix-attempted=yes }}