Post by Alan Kelly

I enjoyed speaking at this conference online this afternoon on the significance of proteases in raw milk for processing, based in large part on the excellent work of Tiziana Racca and Aritra Sinha at School of Food and Nutritional Sciences in University College Cork and our collaborators, including Michael Affolter and Anthony O'Donoghue. The key message was that in raw milk protease activity is very dependent on pH and processing and that, at native milk pH, plasmin certainly dominates the proteolysis landscape but produces relatively few fragments, while a complex multi-enzyme system is also present. The picture at acidic pH is completely different, including the activity of a newly discovered (by Tiziana) tripeptidyl aminopeptidase. In addition, all this is further complicated by effects of season, lactation and other factors, while pasteurisation completely reshapes the landscape, simplifying it but greatly amplifying the activity of plasmin, to an extent not always perhaps appreciated. And that's before we even think about bacterial proteases, the roles of which are greatly underestimated as a factor in raw milk quality in our opinion. Great progress but lots of fun scientific challenges yet to solve! AEDIL Dairy CoVe Lilia Ahrné Milena Corredig Seamus O'Mahony Norbert Raak