R. W. Mandigo

Inhibition of Listeria monocytogenes by bacteriocin-producing Pediococcus during the manufacture of fermented semidry sausage.

A bacteriocin-producing Pediococcus species inhibitory to Listeria monocytogenes was used to manufacture fermented semidry sausage. Separate 13.6 kg batches of a commercial summer sausage formulation were inoculated to contain an initial level of 106 cells/g of Listeria monocytogenes Scott A. In each of two independent studies, an ca. 2 log10 CFU/g reduction of L. monocytogenes occurred over the fermentation period, as compared to a less than 1 log10 CFU/g reduction in sausage fermented with a non-inhibitory Pediococcus strain. Inactivation of L. monocytogenes was also observed in one study where adequate acid production did not occur (pH>5.5), indicating that bacteriocin production occurred independently of carbohydrate fermentation. Following heating to an internal temperature of 64.4°C and storage up to 2 weeks, 9 of 90 sausages sampled were positive for Listeria . Recovery was intermittent and did not indicate that the bacteriocin was effective in eliminating L. monocytogenes that had survived the heating process.

The use of bacteriocin-producing Pediococcus acidilactici to control postprocessing Listeria monocytogenes contamination of frankfurters

The ability of a bacteriocin-producing Pediococcus acidilactici to control postprocessing Listeria monocytogenes contamination of frankfurters was examined. Bacteriocin-producing P. acidilactici JD1-23 or its plasmid-cured derivative JD-M and a five-strain composite of L. monocytogenes were inoculated onto fully processed frankfurters. Under normal storage conditions at 4°C under vacuum, L. monocytogenes without added pediococci grew from an initial level of 104 CFU/g to a final level of 106 CFU/g over 60 d, with a lag time of 20-30 d. Under the same conditions, high levels (107 CFU/g) of either pediococcal strain inhibited growth of L. monocytogenes up to 60 d, although no reduction of cells occurred. With low levels of pediococci (103-104 CFU/g), Listeria grew, although the lag time was increased, and a bacteriocin effect was observed on frankfurters inoculated with JD1-23. In additional experiments done at 4°C and 15°C under aerobic and anaerobic conditions, levels of 107-108 CFU/g of either pediococci were observed to control Listeria growth on frankfurters at 15°C under anaerobic conditions for up to 15 d. At 4°C under aerobic conditions, L. monocytogenes grew on frankfurters inoculated with JD-M, while JD1-23 inhibited growth of the organism up to 30 d. At 15°C under aerobic conditions, L. monocytogenes grew in the presence of either pediococci, although a bacteriocin effect was indicated. Package atmosphere was observed to affect L. monocytogenes growth on this product.

Evaluation of a phosphate to control pathogen growth in fresh and processed meat products

The efficacy of a phosphate blend, Bekaplus MSP, to inhibit the growth of foodborne pathogens in fresh or processed meat products was studied. The following products and challenge microorganisms were tested: ground beef, Escherichia coli O157:H7; linked smoked sausage, Salmonella typhimurium and L. monocytogenes ; cured smoked ham, S. typhimurium and L. monocytogenes ; and fresh pork sausage, E. coli O157:H7. All the products were prepared with or without 0.5% phosphate, individually inoculated with the challenge microorganism (103CFU/g of meat), and stored at either 4, 12, or 20°C. There was minimal or no effect of the phosphate blend on the growth of L. monocytogenes or S. typhimurium . The temperature of storage had a significant effect (P < 0.05) on the population of E. coli O157:H7 in ground beef and fresh pork sausage with phosphate. However, the presence of phosphate in the ground beef had no effect (P > 0.05) on E. coli O157:H7, but the presence of phosphate in the fresh pork sausage had a significant effect (P < 0.05) on controlling E. coli O157:H7. These results indicate that this phosphate blend could be used in fresh pork sausage to help inhibit the growth of E. coli O157:H7.

Preparation Method and Final Internal Temperature Influences on Boneless Pork Loin Roast Quality Characteristics

Abstract Nationally pork is selected as a meat choice approximately 25% of the time. Characterizing yield and quality attributes may enhance consumption of lean pork cuts. Yield and quality evaluation of 1.4 kg boneless pork loins (NAMP No. 414) roasted in a 162.8°C conventional oven was completed using a strip split plot experimental design, a two {two internal temperatures (71, 82°C)} × three {three cooking methods {roast, braise, cook in bag}} factorial treatment design and four replications. Dependent variable measurements included yield, color, expressible moisture and objective tenderness (LEE Kramer Shear). Sensory tenderness, juiciness and pork flavor intensity were evaluated using a 15 cm anchored line (1 = less tender, dry and lack of flavor; 15=tender, moist and abundance of flavor). Yield and sensory characteristics were not different for roasts cooked to 71 or 82°C (P