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dc.contributor.advisorHolo, Helge
dc.contributor.advisorHeir, Even
dc.contributor.advisorLangsrud, Solveig
dc.contributor.authorFossmo, Sabine
dc.date.accessioned2013-07-09T12:12:20Z
dc.date.issued2013-07-09
dc.identifier.urihttp://hdl.handle.net/11250/186635
dc.description.abstractKontroll med bakterier som Listeria utgjør en stor utfordring for mange matprodusenter. Listeria monocytogenes er hovedsakelig et produksjonshygienisk problem, forbedret hygiene kan derfor være tiltak for å redusere overlevelse og smitteoverføring av bakterien i produksjonsmiljø. Hensikten med forsøkene i oppgaven var å undersøke effekten av ulike desinfeksjonsstrategier på drap av L. monocytogenes, både når bakteriene var i biofilm og i suspensjon. Dette inkluderte bruk av tradisjonelle desinfeksjonsmidler etterfulgt av hypokloritt og klordioksid, i tillatte konsentrasjoner i drikkevann, i skyllevannet etter desinfeksjon. Det ble benyttet en blanding av seks L. monocytogenes stammer isolert fra lakse- og kjøttindustrien. Biofilm ble dannet på stålkuponger over to døgn ved 20 °C. Biofilmen ble utsatt for desinfeksjon med hypokloritt, pereddiksyre og benzalkoniumklorid etterfulgt av hypokloritt og klordioksid i skyllevannet. L. monocytogenes i suspensjon ble eksponert for de samme konsentrasjonene av desinfeksjonsmiddel og antimikrobielle komponenter i skyllevannet. Det ble benyttet desinfeksjonsmiddelkonsentrasjoner som ga under to log drap i første desinfeksjonstrinn for å kunne måle drapseffekt og eventuelle samspillseffekter med de antimikrobielle komponentene i skyllevannet. Klordioksid i skyllevannet var effektivt mot L. monocytogenes i biofilm, hvor det ledet til signifikant større totaldrap, på 2 log (2 x større drap), i kombinasjon med pereddiksyre (p=0,002) og 1 log i kombinasjon med benzalkoniumklorid (p=0,014). Hypokloritt som desinfeksjon var svært effektiv mot biofilm dannet av L. monocytogenes, hvilket gjorde det vanskelig å detektere ytterligere drap av de antimikrobielle komponentene i skyllevannet. Klordioksid, med konsentrasjonene 0,5 og 1 ppm, i skyllevannet var effektivt mot L. monocytogenes i suspensjon, hvor det ledet til signifikant større totaldrap, på over 3 log, i kombinasjon med pereddiksyre (p=0,000), over 4 log i kombinasjon med hypokloritt (p=0,000) og 1 ppm klordioksid ga et signifikant større totaldrap på 3 log i kombinasjon med benzalkoniumklorid (p=0,026). Hypokloritt i skyllevannet førte til et signifikant større totaldrap, på 2 log, i kombinasjon med pereddiksyre både på L. monocytogenes i biofilm (p=0,002) og i suspensjon (p=0,050) samt i kombinasjon med benzalkoniumklorid på bakterier i biofilm (p=0,016). Hypokloritt i skyllevannet ga også et større totaldrap, på 1,5 log, i kombinasjon med hypokloritt som desinfeksjon på bakterier i suspensjon, men dette var ikke signifikant. Pereddiksyre økte drapseffekten av klordioksid i skyllevannet både på L. monocytogenes i biofilm og i suspensjon. Hypokloritt som desinfeksjon førte til signifikant økt effekt av 0,5 ppm klordioksid i skyllevannet på bakterier i suspensjon. Pereddiksyre økte drapseffekten av hypokloritt i skyllevannet på bakterier i suspensjon. Dette indikerer at bruk av hypokloritt og klordioksid i skyllevann etter desinfeksjon kan gi økt drap av L. monocytogenes både i biofilm og i suspensjon, hvor kombinasjon av desinfeksjonsmidler med samme virkningsmekanismer viste tendens til å gi størst totaldrap. ABSTRACT Control of bacteria, as Listeria, is a major challenge in the food manufacturing industry. Listeria monocytogenes is mainly a hygienic problem, enhanced hygiene can therefore be used to reduce survival and transmission of the bacteria in the production environment. The purpose of this study was to evaluate different disinfection strategies on L. monocytogenes, both bacteria in biofilms and in suspension. This included the use of traditional disinfectants followed by hypochlorite and chlorine dioxide, in concentrations that is legally in drinking water, in rinsing water after disinfection. Six L. monocytogenes strains isolated from salmon- and meatindustry were used in the research. The biofilms were initially formed on stainless steel coupons for two days at 20 °C. The biofilm was subjected to disinfection with hypochlorite, peracetic acid and benzalkonium chloride followed by hypochlorite and chlorine dioxide in the rinsing water. L. monocytogenes in suspension were exposed to the same concentrations of disinfectant and antimicrobial components in the rinse water. The concentrations of disinfectants that gave approximately two log reduction were selected in the first disinfection step, which made it possible to measure log reduction and possible interactions with the antimicrobial component in the rinsing water. Chlorine dioxide in the rinsing water was effective against L. monocytogenes in biofilm. Chlorine dioxide increased total log reduction with 2 log (2 x greater reduction), in combination with peracetic acid (p=0,002) and with 1 log in combination with benzalkonium chloride (p=0,014) as the first disinfectants. Hypochlorite as disinfectant was very effective on L. monocytogenes in biofilm, which made it difficult to detect further reduction from antimicrobial components in the rinsing water. Chlorine dioxide, in concentrations of 0.5 and 1 ppm, in the rinse water was effective on L. monocytogenes in suspension. Where it led to significant greater log reduction, over 3 log, in combinations with peracetic acid (p=0,000), over 4 log in combination with hypochlorite (p=0,000) and 1 ppm chlorine dioxide gave 3 log greater reduction in combination with benzalkonium chloride (p=0,026). Hypochlorite in the rinse water increased log reduction with 2 log in combinations with peracetic acid both on L. monocytogenes in biofilm (p=0,002) and in suspension (p=0,050), and in combination with benzalkonium chloride on bacteria in biofilm (p=0,016). Hypochlorite in the rinse water also led to 1.5 log reduction in combination with hypochlorite as disinfectant on bacteria in suspension, but this was not significant. Peracetic acid as disinfectant increased the effect of chlorine dioxide in rinsing water both on L. monocytogenes in biofilm and in suspension. Hypochlorite as disinfectant increased the effect of 0.5 ppm chlorine dioxide in the rinsing water on bacteria in suspension. Peracetic acid increased the effect of hypochlorite in rinsing water on bacteria in suspension. This indicates that antimicrobial components in the rinsing water after disinfection may increase reduction of L. monocytogenes, both in biofilm and in suspension. Combinations of disinfectants with the same mechanism of action showed greatest total log reduction.no_NO
dc.description.abstractControl of bacteria, as Listeria, is a major challenge in the food manufacturing industry. Listeria monocytogenes is mainly a hygienic problem, enhanced hygiene can therefore be used to reduce survival and transmission of the bacteria in the production environment. The purpose of this study was to evaluate different disinfection strategies on L. monocytogenes, both bacteria in biofilms and in suspension. This included the use of traditional disinfectants followed by hypochlorite and chlorine dioxide, in concentrations that is legally in drinking water, in rinsing water after disinfection. Six L. monocytogenes strains isolated from salmon- and meatindustry were used in the research. The biofilms were initially formed on stainless steel coupons for two days at 20 °C. The biofilm was subjected to disinfection with hypochlorite, peracetic acid and benzalkonium chloride followed by hypochlorite and chlorine dioxide in the rinsing water. L. monocytogenes in suspension were exposed to the same concentrations of disinfectant and antimicrobial components in the rinse water. The concentrations of disinfectants that gave approximately two log reduction were selected in the first disinfection step, which made it possible to measure log reduction and possible interactions with the antimicrobial component in the rinsing water. Chlorine dioxide in the rinsing water was effective against L. monocytogenes in biofilm. Chlorine dioxide increased total log reduction with 2 log (2 x greater reduction), in combination with peracetic acid (p=0,002) and with 1 log in combination with benzalkonium chloride (p=0,014) as the first disinfectants. Hypochlorite as disinfectant was very effective on L. monocytogenes in biofilm, which made it difficult to detect further reduction from antimicrobial components in the rinsing water. Chlorine dioxide, in concentrations of 0.5 and 1 ppm, in the rinse water was effective on L. monocytogenes in suspension. Where it led to significant greater log reduction, over 3 log, in combinations with peracetic acid (p=0,000), over 4 log in combination with hypochlorite (p=0,000) and 1 ppm chlorine dioxide gave 3 log greater reduction in combination with benzalkonium chloride (p=0,026). Hypochlorite in the rinse water increased log reduction with 2 log in combinations with peracetic acid both on L. monocytogenes in biofilm (p=0,002) and in suspension (p=0,050), and in combination with benzalkonium chloride on bacteria in biofilm (p=0,016). Hypochlorite in the rinse water also led to 1.5 log reduction in combination with hypochlorite as disinfectant on bacteria in suspension, but this was not significant. Peracetic acid as disinfectant increased the effect of chlorine dioxide in rinsing water both on L. monocytogenes in biofilm and in suspension. Hypochlorite as disinfectant increased the effect of 0.5 ppm chlorine dioxide in the rinsing water on bacteria in suspension. Peracetic acid increased the effect of hypochlorite in rinsing water on bacteria in suspension. This indicates that antimicrobial components in the rinsing water after disinfection may increase reduction of L. monocytogenes, both in biofilm and in suspension. Combinations of disinfectants with the same mechanism of action showed greatest total log reduction.
dc.language.isonobno_NO
dc.publisherNorwegian University of Life Sciences, Ås
dc.subjectListeria monocytogenesno_NO
dc.subjectDesinfeksjonno_NO
dc.subjectHypoklorittno_NO
dc.subjectKlordioksidno_NO
dc.subjectPereddiksyreno_NO
dc.subjectBenzalkoniumkloridno_NO
dc.subjectHygieneno_NO
dc.subjectRenholdno_NO
dc.subjectPatogenno_NO
dc.subjectBakterierno_NO
dc.subjectPersistensno_NO
dc.titleEffekt av ulike desinfeksjonsstrategier mot Listeria monocytogenesno_NO
dc.title.alternativeEffect of various disinfection strategies against Listeria monocytogenesno_NO
dc.typeMaster thesisno_NO
dc.subject.nsiVDP::Technology: 500::Food science and technology: 600no_NO
dc.description.embargo2018-05-15
dc.source.pagenumber75no_NO
dc.relation.projectNofimano_NO


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