Characterization of anti-listerial bacteriocin produced by lactic acid bacteria isolated from traditional fermented foods from Cambodia

info:eu-repo/semantics/publishedVersio

Effect of protective cultures and different modified atmosphere packaging on Listeria innocua growth and on sensory properties in sliced cured-smoked pork loin

This study aims to evaluate the antimicrobial effect of two protective cultures combined with different modified atmosphere packaging (MAP) systems on Listeria innocua growth in sliced ready-to-eat pork loin, a Portuguese traditional cured-smoked product (Lombo). Two protective lactic acid (LAB) cultures - Lactobacillus sakei ST153 and BLC35 (CHR Hansen) were tested for their ability against L. innocua 20130c growth (as a surrogate for L. monocytogenes) in sliced “lombo” packed in two MAP conditions, (20%CO2/80%N2 and 40%CO2/60%N2) and stored at 5oC. The influence of MAP and protective cultures in the sensory characteristics of the product was also evaluated by semi-trained panel of fifteen judges. The MAP affected the growth of L. innocua, the Listeria population decreasing 3 log CFU/g after 120 days of storage at 5oC. In samples containing protective cultures a reduction of 1–2 log CFU/g in counts of L. innocua was observed after 12 hours. At the end of storage results indicated that L. sakei ST 153 was more efficient than BLC35 culture on inhibiting L. innocua growth and this inhibition was enhanced by MA (40%CO2/60%N2). Results of sensory evaluation showed that oiliness, hardness, succulence, and characteristic taste attributes of “lombo” decreased during storage whereas the bitter taste increased in both LAB applications and no significant differences between LAB cultures or MAP conditions were found

Enhancement of bacteriocin production and antimicrobial activity of Pediococcus acidilactici HA-6111-2

The effect of sequential treatments of pressure (50–150 MPa, 10 ºC, 5 min) and temperature (57 ºC, 15 min) on the survival and bacteriocin production of Pediococcus acidilactici HA-6111-2 cells in the exponential growth phase was assessed. The growth curves were fitted with the modified Gompertz model, and the estimated maximum specific growth rate was considered to be pressure dependent. A delay in the maximum value of bacteriocin production was registered for more severe pressure conditions, but it was found more notorious for pressure followed by temperature treatments. At lower pressure intensity treatment, regardless of the application order, there was an enhancement of bacteriocin production per cell when compared to the control while maintaining the maximum production value. Bacteriocin production after the treatments can be described by an exponential model

Effect of high pressure on growth and bacteriocin production of Pediococcus acidilactici HA-6111-2

This study was aimed to investigate the effect of high pressure processing (HPP, 200-600MPa) on the (i) survival of Listeria innocua and Pediococcus acidilactici HA-6111-2; (ii) production of bacteriocin bacHA-6111-2 and (iii) activity of bacteriocin against untreated and pressure-treated L. innocua cells. Inactivation of P. acidilactici was observed for pressures of >300MPa. However, at this pressure level, L. innocua was more sensitive. Bacteriocin crude extract was pressure stable, with a decrease for pressures of 400 MPa. Pressures of 200MPa did not affect bacteriocin production when compared with non-pressure-treated cells, whereas higher pressures caused a 2- to 4-fold decrease on the maximum level of bacteriocin production. Growth curves of P. acidilactici were fitted with the modified Gompertz model. The lag phase period depended on the magnitude of the pressure applied: there was a delay in the exponential phase as pressure increased and, as a consequence, in the beginning of bacteriocin production. Since P. acidilactici HA-6111-2 and its bacteriocin have shown resistance to pressures up to 300-400 MPa, they could be used in combination with HPP in order to improve food safety.info:eu-repo/semantics/publishedVersio

Persistent and non-persistent strains of Listeria monocytogenes: A focus on growth kinetics under different temperature, salt, and pH conditions and their sensitivity to sanitizers

This study aimed to investigate the effect of different conditions, including temperature (37 C, 22 C, and 4 C), NaCl concentrations (2.5%, 4%, and 8%), and acidity (pH ¼ 5), on the growth response of persistent and non-persistent isolates of Listeria monocytogenes. The resistance to two common sanitizers (benzalkonium chloride and hydrogen peroxide) was also investigated. A selected group of 41 persistent and non-persistent L. monocytogenes isolates recovered from three cheese processing plants during a previous longitudinal study was assembled. Average lag time was similar for persistent and non-persistent isolates grown at 37 C, 22 C and 4 C but significantly shorter (p < 0.05) for persistent isolates grown at 2.5%, 4% and 8% NaCl, and at pH 5. Average growth rates were significantly higher (p < 0.05) for persistent than for non-persistent isolates when grown at 22C, 2.5%, 4% and 8% NaCl, and at pH 5. These results suggest that persistent strains may be better adapted to grow under stressful conditions frequently encountered in food processing environments than non-persistent strains. No relation between persistence and resistance to the tested sanitizers was found.info:eu-repo/semantics/publishedVersio

Biopreservation strategies in combination with mild high pressure treatments in traditional Portuguese ready-to-eat meat sausage

Thrombomodulin (TM) is an endothelial cell membrane protein that acts as a major cofactor in the protein C anticoagulant pathway. The EGF-like domains 4-6 of TM (TM456) are essential for PC activation. In this study, we proposed a liposomal recombinant TM conjugate to mimic the membrane TM structure and its anticoagulant activity. First, a DSPE-PEG2000-TM456 was successfully synthesized by site-specific conjugation of azido-TM456 with DSPE-PEG2000-DBCO via copper-free click chemistry quantitatively. Then, liposome-TM456 was fabricated via direct liposome formation with the DSPE-PEG2000-TM456 and other lipids. This liposomal formulation of TM456 retained protein C activation activity as that of TM456. Also, liposome-TM456 was much more stable and had a longer plasma half-life than TM456 and DSPE-PEG2000-TM456, respectively. Moreover, liposome-TM456 showed in vivo anticoagulant effect by decreasing the mortality from 80% to 20% in a thrombin-induced thromboembolism mouse model. The reported liposome-TM456 conjugate mimics the endothelial TM anticoagulation activity and may serve as an effective anticoagulant agent candidate for future development.info:eu-repo/semantics/publishedVersio

Combined effect of pediocin bacHA-6111-2 and high hydrostatic pressure to control listeria innocua in fermented meat sausage

In and ex situ production of bacteriocin (bacHA-6111-2) combined with high hydrostatic pressure (300 MPa, 5 min, 10ºC) were assessed on the survival of Listeria innocua reviously inoculated in Alheira, a traditional Portuguese fermented meat product. The effect was evaluated immediately after each treatment, alone and combined, and during 60 days of storage (4ºC). For higher concentrations of L. innocua, a bacteriostatic effect was verified: i) during the first days of storage for the pressure treatment alone and in combination with ex situ production of bacteriocin; and ii) for longer periods, when pressure was combined with in situ production of bacteriocin. After this effect, the first treatments revealed rapid growth up to the initial values; while the latest treatment, and for lower initial cells, resulted in a decrease > 2 log CFU g-1, from day 3 of storage until the end of the study. A similar result was obtained for analogous pressurized L. innocua samples with ex situ production of bacteriocin. The developed work has demonstrated the potential of using the combination of natural antimicrobial compounds (pediocin bacHA-6111-2, produced either in or ex situ) with mild pressure (300 MPa, 5 min) treatments to control effectively L. innocua in fermented meat products such as Alheiras, when contaminated with values closed to the ones that might potentially arise by natural postcontamination.info:eu-repo/semantics/publishedVersio

Effect of protective cultures and different modified atmosphere packaging on Listeria innocua growth and on sensory properties in sliced cured-smoked pork loin

This study aims to evaluate the antimicrobial effect of two protective cultures combined with different modified atmosphere packaging (MAP) systems on Listeria innocua growth in sliced ready-to-eat pork loin, a Portuguese traditional cured-smoked product (Lombo). Two protective lactic acid (LAB) cultures - Lactobacillus sakei ST153 and BLC35 (CHR Hansen) were tested for their ability against L. innocua 20130c growth (as a surrogate for L. monocytogenes) in sliced “lombo” packed in two MAP conditions, (20%CO2/80%N2 and 40%CO2/60%N2) and stored at 5oC. The influence of MAP and protective cultures in the sensory characteristics of the product was also evaluated by semi-trained panel of fifteen judges. The MAP affected the growth of L. innocua, the Listeria population decreasing 3 log CFU/g after 120 days of storage at 5oC. In samples containing protective cultures a reduction of 1–2 log CFU/g in counts of L. innocua was observed after 12 hours. At the end of storage results indicated that L. sakei ST 153 was more efficient than BLC35 culture on inhibiting L. innocua growth and this inhibition was enhanced by MA (40%CO2/60%N2). Results of sensory evaluation showed that oiliness, hardness, succulence, and characteristic taste attributes of “lombo” decreased during storage whereas the bitter taste increased in both LAB applications and no significant differences between LAB cultures or MAP conditions were found.</p