Microscopy-Based Identification of Blood Products, Milk, and Hydrolyzed Proteins in Animal Feed Under Regulation (EU) 152/2009: Current Challenges

Under EU legislation, the use of blood products, milk, and hydrolyzed proteins in animal feed is regulated to ensure safety and prevent the spread of disease. These materials are classified as animal by-products (ABPs) and their use is restricted to prevent risks associated with transmissible spongiform encephalopathies (TSEs) and other potential hazards. Specific EU regulations outline official methods for detecting processed animal proteins (PAPs) in feed, primarily through light microscopy and polymerase chain reaction (PCR). Microscopic identification remains challenging, particularly when distinguishing particles such as milk globules, plasma residues, and hydrolyzed proteins. This review highlights these limitations and emphasizes the urgent need for enhanced training and refined techniques to improve the accuracy and reliability of microscopic analysis in complex samples.