Protein Dispersibility Index
Encyclopedia
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.
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.
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.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
in water, and is widely used in the soybean
Soybean
The soybean or soya bean is a species of legume native to East Asia, widely grown for its edible bean which has numerous uses...
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.
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.
The PDI required of a soyflour is dependent on the purpose to which the soybeans are to be put. Manufacturers of soymilk and tofu
Tofu
is a food made by coagulating soy milk and then pressing the resulting curds into soft white blocks. It is part of East Asian and Southeast Asian cuisine such as Chinese, Japanese, Korean, Indonesian, Vietnamese, and others. There are many different varieties of tofu, including fresh tofu 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.