Factors affecting inactivation of Moraxella-Acinetobacter cells in an irradiation process.

The effect of various stages of the irradiation processing of beef on the injury and inactivation of radiation-resistant Moraxella-Acinetobactor cells was studied. Moraxella-Acinetobacter cells were more resistant to heat inactivation and injury when heated in meat with salts (0.75% NaCl and 0.375% sodium tripolyphosphate) then in meat without salts. These salts had no effect on radiation resistance. Both radiation- and heat-injured cells were unable to form colonies at 30 degrees C in plate count agar containing 0.8% NaCl. Neither unstressed nor heat-stressed cells were able to multiply in minced beef incubated at 30 degrees C for 12 h. Only after the beef was diluted 1:10 with peptone water were the heat-injured cells able to repair and eventually multiply. Heated cells were more sensitive to radiation inactivation and injury than unheated cells. After repair, the cells regained their resistance to both NaCl and irradiation. Freezing and storage at -40 degrees C for 14 days had only a slight effect on either unstressed or heat-stressed cells.