The inhibition effectiveness of a bacteriocin produced by Lactobacillus curvatus CWBI-B28 against Listeria monocytogenes was investigated in cold-smoked salmon during storage at 4 degrees C. Three bacteriocin-based strategies for the control of L. monocytogenes in foods (i.e., producing bacteriocin in situ, spraying with partially purified bacteriocin, and packaging in bacteriocin-coated plastic film), plus a newly developed method that uses cell-adsorbed bacteriocin (i.e., a suspension of producer cells on which maximum bacteriocin has been immobilized by pH adjustments), were assessed. Although all the approaches inactivated L. monocytogenes in cold-smoked salmon, various efficacy levels were observed. The behavior of L. monocytogenes was similar in samples treated with either partially purified bacteriocin or in situ bacteriocin production. In both of these cases, the counts of the pathogen declined to below the detectable limit of 0.7 log CFU/cm2 within the first week, but a approximately 0.95- and 1.3-log increase, respectively, occurred after day 14. The bioactive packaging film resulted in a slower inactivation of the pathogen but prevented any subsequent increase in the CFU throughout 22 days of storage at 4 degrees C. Application of the cell-adsorbed bacteriocin was shown to be the most effective means, as it resulted in a complete inactivation of the pathogen within 3 days, and no increase in Listeria counts occurred up to 22 days.

Aim: Study of the effectiveness of in situ bacteriocin production by lactic acid bacteria (LAB) to control Listeria monocytogenes in dry-fermented sausages. Methods and Results: Two bacteriocin-producing strains: Lactococcus lactis subsp. lactis LMG21206 and Lactobacillus curvatus LBPE were grown in a pilot scale fermentor and lyophilized to be directly used in dry sausage fermentation. A commercial starter culture (Bel'meat TM SL-25) not inhibitory to L. monocytogenes (Bac ) starter) was mixed (1 : 1) with each of the two lyophilized bacteriocin-producing strains to obtain starters active against the pathogen (Bac + starter). Anti-Listeria effectiveness of the Bac + starters was studied in dry-fermented sausages. The meat batter was experimentally contaminated with a mixture of four different strains of L. monocytogenes (10 2 -10 3 CFU g )1 ). The results showed that L. monocytogenes did not grow in any of the contaminated batches, but no significant decrease (P > 0AE05) was observed either in the positive control (no added starter culture) or in samples fermented with the Bac ) starter culture during the fermentation period and up to 15 days of drying. When the Bac + starter contained Lb. curvatus LBPE, cell counts of L. monocytogenes decreased to below the detectable limit (<10 CFU g )1 ) after 4 h of fermentation and no survivors could be recovered by enrichment beyond day 8 of drying. When the Bac + starter culture containing Lc. lactis LMG21206 was used, a decrease in Listeria counts to below the detectable limit was achieved after 15 days of drying. Conclusions: The bacteriocin-producing strains studied may be used as adjunct cultures for sausage fermentations to control the occurrence and survival of L. monocytogenes. Significance and Impact of the Study: Addition of the Bac + strains, especially the Lb. curvatus strain would provide an additional hurdle to enhance the control of L. monocytogenes in fermented meat products.

Aims:  To study the effectiveness of a combination of cell‐adsorbed bacteriocin (CAB; a suspension of producer cells on which maximum bacteriocin has been immobilized by pH adjustments) of a Lactobacillus curvatus strain with oregano or savory essential oil to control Listeria monocytogenes in pork meat at 4°C. Methods and Results:  The antimicrobial activity of the CAB and six different essential oils was tested by the well diffusion assay against L. monocytogenes M, Escherichia coli 10536 and Salmonella serotype Typhi CWBI‐H1. The anti‐Listeria activity of the CAB and oregano or savory essential oils was also investigated in pork meat. The results of the well diffusion assay showed that CAB was only inhibitory to L. monocytogenes while savory and oregano essential oils were the most active against the three indicator bacteria. In pork meat, Listeria counts have declined from c. 102 CFU g−1 to below the detectable limit during the first week of storage in samples treated with CAB or oregano essential oil and in those treated with CAB combined with oregano or savory essential oil. However, the counts of L. monocytogenes have increased after the third week of storage in all samples with the exception of those treated with the combination of CAB and oregano essential oil. The combination of CAB with savory essential oil resulted in a 2‐week delay of the growth rebound compared with samples treated with CAB alone. Conclusions:  Addition of oregano or savory essential oil exhibited a synergistic effect with CAB to control L. monocytogenes in pork meat during storage at 4°C. Significance and Impact of the Study:  The combination of CAB with oregano or savory essential oil may be effectively used in meat industry to enhance the safety and stability of meat products.

The purpose of this study was to immobilize lipase from Yarrowia lipolytica using three methods including inclusion, adsorption, and covalent bond to study enzyme leaching, storage, and catalytic properties. Sodium alginate and chitosan were the polymers selected to immobilize lipase by inclusion. The beads of each polymer were dried by freeze drying and fluidization. The results show that chitosan was more adapted to the inclusion of lipase. Even though freeze dried, bead activity was low compared to that of fluidized beads. The freeze-drying process seems to produce suitable beads for storage at 4 and 20 degrees C. The immobilization by adsorption was carried out on both celite and silica gel. Maximum immobilization yield of 76% was obtained with celite followed by 43% in silica gel. The enzyme adsorbed on the two supports exhibited greater stability at a certain temperature (50 degrees C) and in no polar solvents (Isooctane, n-heptane, and n-hexane). In addition, the lipase immobilized by covalent bond retained residual activity equitable to 70%. It was demonstrated that the enzyme immobilized by covalent bond showed greater activity (80%) after 5 months of storage.