Effect of antimicrobials as ingredients of pork bologna for Listeria monocytogenes control during storage at 4 or 10°C

Sodium or potassium lactate and sodium diacetate are currently included as ingredients in meat products for control of Listeria monocytogenes contamination during storage. This study compared the antilisterial activity of sodium lactate (SL), sodium diacetate (SD) and glucono-delta-lactone (GDL) used as single or combined ingredients at various levels in pork bologna stored under refrigeration (4degrees) or at a mildly abusive temperature (10degrees). Moreover, treatments were evaluated for their influence on the microflora of the product. Inoculated (3-4log cfu/cm(2); 10-strain composite of L. monocytogenes) bologna slices were vacuum-packaged, and stored at 4degreesC or at 10degreesC. Absence of the above antimicrobials from the formulation allowed increases of L. monocytogenes to 8.3 log cfu/cm(2) in 10-20 days and 8.8 log cfu/cm(2) in 8-12 days at 4 and 10degreesC, respectively. Modelling of L. monocytogenes growth as a function of time, indicated that the treatment that resulted in the lowest maximum specific growth rate (mu(max)) was the combination of 1.8% SL with 0.25% SD (0.009 and 0.084day(-1) at 4 and 10degreesC, respectively), followed by the combination of 1.8% SL with 0.125% SD and 0.125% GDL (0.039 and 0.210 day(-1) at 4 and 10degreesC, respectively); the mu(max) of control treatments was 0.609 day(-1) at 4degreesC and 1.34 days at 10degreesC. Lactic acid bacteria (LAB) were the most prominent spoilage organisms isolated from the product. The combination of 1.8% SL with 0.25% SD seemed to be the treatment that controlled growth of LAB more effectively at 4degreesC, while at 10degreesC their growth was inhibited more effectively by 0.125% GDL. These findings indicated that meat processors need to select the most effective combination and concentration of these preservatives to achieve safety as well as the shelf-life necessary for these products. (C) 2004 Elsevier Ltd. All rights reserved.