Heat resistance of Cronobacter species (Enterobacter sakazakii) in milk and special feeding formula

Aim: To determine D- and z-values of Cronobacter species (Enterobacter sakazakii) in different reconstituted milk and special feeding formula and the effect of reconstitution of powdered milk and special feeding formula with hot water on the survival of the micro-organism. Methods and Results: Five Cronobacter species (four C. sakazakii isolates and C. muytjensii) were heated in reconstituted milk or feeding formula pre-equilibrated at 52-58 degrees C for various times or mixed with powdered milk or feeding formula prior to reconstitution with water at 60-100 degrees C. The D-values of Cronobacter at 52-58 degrees C were significantly higher in whole milk (22 center dot 10-0 center dot 68 min) than in low fat (15 center dot 87-0 center dot 62 min) or skim milk (15 center dot 30-0 center dot 51 min) and significantly higher in lactose-free formula (19 center dot 57-0 center dot 66 min) than in soy protein formula (17 center dot 22-0 center dot 63 min). The z-values of Cronobacter in reconstituted milk or feeding formula ranged from 4 center dot 01 degrees C to 4 center dot 39 degrees C. Water heated to >= 70 degrees C and added to powdered milk and formula resulted in a > 4 log(10) reduction of Cronobacter. Conclusions: The heat resistance of Cronobacter should not allow the survival of the pathogen during normal pasteurization treatment. The use of hot water (>= 70 degrees C) during reconstitution appears to be an effective means to reduce the risk of Cronobacter in these products. Significance and Impact of the Study: This study supports existing data available to regulatory agencies and milk producers that recommended heat treatments are sufficient to substantially reduce risk from Cronobacter which may be present in these products.