ABSTRACT
To control the growth, or reduce the numbers, of food pathogens such as Listeria monocytogenes and Campylobacter jejuni in chicken products packaged under modified atmosphere (MAP), the effectiveness of protective cultures was evaluated in this study. Leuconostoc pseudomesenteroides PCK18 reduced the counts of L. monocytogenes by 1.22 log cfu/g in chicken burgers under MAP after 24 d. Furthermore, a reduction of 1.16 log cfu/g in C. jejuni together with a delay in the growth of lactic acid bacteria was obtained in chicken legs inoculated with Bifidobacterium longum ssp. longum PCB133 and packaged under MAP after 9 d. The combination and concentration of gases in the MAP doubled the products' shelf-life in comparison with air-packaged samples in both experiments. In conclusion, this study has shown the effectiveness of 2 protective culture strains against 2 foodborne pathogens, resulting in safer products with a longer shelf-life.
Subject(s)
Bifidobacterium , Campylobacter jejuni/growth & development , Food Preservation/methods , Leuconostoc , Listeria monocytogenes/growth & development , Meat/microbiology , Probiotics/administration & dosage , Air Pressure , Animals , Atmosphere , Campylobacter jejuni/isolation & purification , Chickens , Colony Count, Microbial , Food Microbiology , Listeria monocytogenes/isolation & purification , Meat Products/microbiology , Time FactorsABSTRACT
The high amount of winery wastewaters produced each year makes their treatment a priority issue due to their problematic characteristics such as acid pH, high concentration of organic load and colourful compounds. Furthermore, some of these effluents can have dissolved pesticides, due to the previous grape treatments, which are recalcitrant to conventional treatments. Recently, photo-electro-Fenton process has been reported as an effective procedure to mineralize different organic contaminants and a promising technology for the treatment of these complex matrixes. However, the reactors available for applying this process are scarce and they show several limitations. In this study, a sequential two-column reactor for the photo-electro-Fenton treatment was designed and evaluated for the treatment of different pesticides, pirimicarb and pyrimethanil, used in wine production. Both studied pesticides were efficiently removed, and the transformation products were determined. Finally, the treatment of a complex aqueous matrix composed by winery wastewater and the previously studied pesticides was carried out in the designed sequential reactor. The high removals of TOC and COD reached and the low energy consumption demonstrated the efficiency of this new configuration.
Subject(s)
Hydrogen Peroxide , Industrial Waste , Iron , Waste Disposal, Fluid/methods , Water Purification/methods , Wine , Industrial Waste/analysis , Pesticides , Photolysis , VitisABSTRACT
Escherichia coli and Listeria monocytogenes microbial challenge tests were performed on fresh suckling-lamb meat. Hind leg slices were chilly stored under two modified atmosphere packaging (MAP) environments (A: 15%O2/60%CO2/25%N2, B: 15%O2/30%CO2/55%N2) and vacuum packaging (V). Only E. coli was reduced between 0.72-1.25 log cfu/g from day 1 to day 4 by the combined use of MAP/V, chilling storage and the growth of native lactic acid bacteria. However, L. monocytogenes was not inhibited by the application of V or MAP. Even do, in inoculated samples, this pathogen increased between 1.2-2.7 log cfu/g throughout the study. Consequently, a second experiment that combined the effects of MAP/V and a protective culture (Leuconostoc pseudomesenteroides PCK 18) against L. monocytogenes was designed. Two different levels of protective cultures were assayed (4 and 6 log cfu/g). Lc. pseudomesenteroides PCK 18 was able to control the growth of L. monocytogenes when the differences between them are higher than 2 log cfu/g. Moreover, when high level of protective culture was used a significant reduction of L. monocytogenes counts were noticed in samples packaged in 60% of CO2 along the storage period, although sensory properties were also affected.
Subject(s)
Bacteriological Techniques , Escherichia coli/isolation & purification , Food Microbiology/methods , Listeria monocytogenes/isolation & purification , Meat/microbiology , Animals , Animals, Suckling , Food Packaging , Meat/standards , SheepABSTRACT
1. Controlled tryptic digestion of native arginase from rat liver suggests that Mn2+ promotes a stable conformation as shown by the following features. 2. An 18-fold increase in the half-life of arginase activity in the presence of Mn2+ is produced. 3. The stability of subunit B of arginase is increased in the presence of Mn2+ as revealed by SDS-PAGE during the time-course of trypsin cleavage. 4. The different digestion products of arginase with and without Mn2+ appearing during the time-course of tryptic treatment. 5. Different activity/bands protein ratio at any time of the tryptic digestion in the incubation mixtures, with and without Mn2+, are apparent.