Managing Contaminated Animal and Plant Materials: Field Guide on ...

The carcasses of several kinds of animals—cattle,swine, poultry, sheep, goats,fish, <strong>and</strong> wild birds—can be treated in thelactic acid fermentation, phosphoric acidpreservation, <strong>and</strong> carcass biogas productionsystems. However, none of these options caninactivate abnormal proteins (prions).In the lactic acid fermentation process,lactic acid bacteria are added to ground carcassesmixed with fermentable carbohydratesto produce lactic acid under anaerobic conditions.These bacteria may produce volatileacids, hydrogen peroxide, <strong>and</strong> antibiotic-likecompounds that inhibit many bacteria.In the phosphoric acid preservationprocess, phosphoric acid is added directlyto ground or small pieces of carcasses. Thephosphoric acid disrupts the membrane functionsof the microorganisms, reducing theirdisease-causing activity.Lactic acid fermentation <strong>and</strong> phosphoricacid preservation are called minor digestion orstabilization processes. They cause little noticeablechange in protein structure, whereascarcass biogas production changes the proteinmaterials considerably.Lactic acid fermentation <strong>and</strong> phosphoricacid preservation not only destroy or inactivatemost disease-causing microorganisms,but also create an acidic pH that picklesthe carcass materials, enabling them to bepreserved safely for up to 4 months if theyremain immersed at the proper chemical concentrations.Carcass pickling is used for decontamination<strong>and</strong> long-term storage of dead poultry.Most rendering companies accept carcassespickled in acid because they are ready forcooking <strong>and</strong> meal production.Compared to cold storage, lactic acidfermentation costs less to preserve ground <strong>and</strong>homogenized poultry carcasses <strong>and</strong> transportthem to rendering facilities. However, in lacticacid fermentation, the costs of the additives267267