Effect of moisture increase during conditioning process

The main preoccupation of feed industry nowadays is the production of safe and hygienic correct animal feed. It is conditioned by the quality of raw materials, applied technological procedures and stability of the product in the storage conditions. Thermal processing (pelleting, extrusion, expansion, etc.) is one of the most efficient manners for reducing presence of the microorganisms in feed. Complete mixture for pigs II was conditioned up to moisture content of 15.97 %, 19.40 %, and 21.88 %. Conditioned material was pelleted on flat die pellet press, and pellets were stored. To evaluate microbiological quality and safety of complete mixture for pigs, samples were analyzed before processing, after conditioning, after pelleting and during storage period (24 hours and 15 days, respectively). Microbiological safety of analyzed products was evaluated in accordance with the regulations of Serbia. Experimental results have shown significant (p< 0.05) reduction of total count of bacteria (from 350.000400.000/g to 100-4000/g) and moulds (from 20.000-25.000/g to 0-800/g) during conditioning and pelleting process. During 24 hour storage of pellets, increase of microbiological growth occurred in material conditioned to highest moisture content. Coagulase positive staphylococci, E. coli, Salmonella and Proteus species were not detected in analyzed samples. Sulphite reducing Clostridia were detected in all samples, but their number was below the limits prescribed by the Regulation, ranging from 100-200/g. Amount of water added during conditioning has determined temperature profile during pelleting and moisture content of pellets during storage, parameters which are highly influencing microbiological growth.