DETECTION OF HEAT-STABLE PROTEINS FROM MEAT OF RUMINANT

摘要

A method is provided for concentrating heat stable proteins in immunogenic extracts prepared from rendered animal materials, and compounds feeds containing these, thus increasing the sensitivity of tests such as immunoassays when they incorporate such preparative method as a preliminary step. A first aspect of the present invention provides a method for pretreating heat stable proteins derived from a rendered animal material prior to performing an assay for their presence comprising (a) preparing a protein containing extract of the material, (b) removing substantially all or part of the gelatin from the extract, preferably with plant protein and oils, and (c) concentrating the remaining protein such that it tests positive for protein. Preferably by immunoassay at a dilution of greater than 1 in 6,000 for rendered meat and bonemeal and at 1 in 400 for compound feeds. The method particularly comprises preparing a liquid buffered extract of the rendered material, removing solid material, e.g. by filtering, adding a salt to the extract at such a concentration as to cause preferential precipitation of gelatin, separating the gelatin precipitate from the extract, increasing the concentration of the salt until a substantial portion of the remainder of the protein is precipitated, and isolating that protein. Preferred salts are ammonium salts, particularly ammonium sulphate. Preferential precipitation of gelatin is conveniently carried out by adding sufficient of the salt to the buffered extract to provide between a 30 and 70 % weight salt solution. In order to precipitate the heat stable proteins once the gelatin has been removed further ammonium sulphate is added to give a final concentration in excess of 80 % weight and preferably about 92.5 % weight.