How does processing of protein affect digestion and absorption?
The digestibility and the rate of amino acid absorption are important factors that determine the nutritional quality of a protein.
Milk contains both whey and micellar casein protein (~20 and 80 % of total protein content, respectively). Whey is a fast digesting protein. In contrast, micellar casein is a slow digesting protein.
However, micellar casein can be processed to caseinate. Caseinate is more soluble than micellar casein and is believed to be more rapidly digested and absorbed.
Caseinate protein can be further processed by cross-linking enzymes to change properties such as its firmness and viscosity.
However, these three casein forms have not been directly compared before.
In this study we compared the plasma amino acid response following the ingestion of micellar casein, caseinate, and cross-linked caseinate.
Subjects received 40 g of one of the drinks and blood samples were taken over a 6-hour period afterwards. Subjects had three different test days for the three different drinks.
Surprisingly, micellar casein appeared to be more relatively rapidly digested and absorbed than expected of a ‘slow’ protein. In fact, it was even faster than the (calcium) caseinate. However, the cross-linked sodium caseinate appeared to be the most rapidly digesting protein.
Although there’s no clear explanation for these unexpected findings, they are likely possibly related to the processing and/or storage of the protein powders, which can alter solubility and other factors related to digestion and absorption.
Therefore, a certain type of protein may behave differently from company to company, from batch to batch, or even based on its shelf life.
Go to the next infographic in the protein series:
Protein supplementation increases muscle mass (but just a bit?)
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