An in vitro protocol to characterise the resistance of food proteins to intestinal digestion.

In vitro digestion tests provide data on the form in which dietary proteins maybe presented to the gut mucosal immune system, one of many strands of evidence used in allergenicity risk assessment. A 96-well plate format in vitro intestinal digestion protocol has been developed with a high and low enzyme activity test executed at pH 6.5 and 8.0. It was applied to the systematic analysis of test proteins (including six allergens and one non-allergenic comparator) which were either completely resistant to pepsinolysis or gave rise to large persistent fragments following in vitro gastric digestion. Digestion was monitored using SDS-PAGE and densitometry. Proteins resistant to pepsin were also resistant to intestinal digestion irrespective of the protocol applied and gave rise to large persistent digestion fragments. In contrast persistent fragments from pepsin digestion were readily digested. Bile salts enhanced the digestibility of two highly resistant proteins, lysozyme ad β-lactoglobulin, changing the rank order of protein digestibility. Intestinal digestion tests that include bile salts provide a more physiologically relevant system for future investigation into how digestion products may influence the balance between tolerance and sensitization - and hence contribute to future development of a more effective allergenicity risk assessment process.