Utjecaj autohtonih sojeva Lactobacillus sakei na mikrobiotu kobasica od mesa divlje svinje

master's thesis

• Title (english): Influence of domestic Lactobacillus sakei strains on microbiota of fermented sausages produced from wild boar meat
• Author: Helena Senko
• Mentor: Mirna Mrkonjić Fuka (mentor)
• Committee member: Mirna Mrkonjić Fuka (predsjednik povjerenstva)
• Committee member: Danijel Karolyi (član povjerenstva)
• Committee member: Ivica Kos (član povjerenstva)
• Granter: University of Zagreb; Faculty of Agriculture; (Department of Microbiology); Zagreb
• Defense date and country: 2017-09-28, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Agronomy

Abstract

Priprema domaćih trajnih fermentiranih kobasica je dio gastronomske tradicije u Hrvatskoj. Međutim, budući da se proizvode bez dodatka starter kultura, mikrobiološka sigurnost gotovih proizvoda može biti upitna. Jedan od načina osiguranja mikrobiološke stabilnosti trajnih kobasica je aplikacija starter i/ili bioprotektivnih kultura. Lactobacillus sakei predstavlja jednu od najkompetitivnijih bakterija mliječne kiseline (BMK) sa prirodnom mikrobiotom mesa. U ovom istraživanju, u smjesu za proizvodnju kobasica, dodana su 2 soja Lb. sakei (MRS_296 i C_7d_13), koja su prethodno izolirana iz kobasica ovog tipa i detaljno tehnološki i molekularno-biološki karakterizirana. Praćeno je preživljavanje dodanih starter kultura tijekom fermentacije i zrenja kobasica, kao i njihov utjecaj na fizikalno-kemijske karakteristike i prirodno prisutnu mikrobiotu. Zabilježen je signifikantno niži pH kod inokulirane kobasice nakon 7 dana (p<0,001) i 40 dana (p<0,001), u odnosu na kontrolnu kobasicu. Dodatno je potvrđena korelacija između broja detektiranih laktobacila i pada pH kod inokulirane (r=-0,97, p<0,001) i kontrolne kobasice (r= -0,81, p<0,05). Analizom rep-PCR obrazaca utvrđeno je da inokulirani starter soj Lb. sakei C_7d_13 ne preživljava, dok je soj MRS_296 pokazao dobru kompetitivnosti sa prirodno prisutnom mikrobiotom budući da je izoliran kao dominantan soj tijekom svih vremenskih intervala, uključujući i gotove proizvode (kraj zrenja) te je u inokuliranoj kobasici broj E.coli, koliformnih bakterija i S. aureus je pao ispod razine detekcije. Međutim, dopušteni broj enterobakterija prelazi granice u inokuliranoj i kontrolnoj kobasici.

Abstract (english)

The production of spontaneously fermented game meat sausages represents a part of the gastronomic tradition in Croatia. However, since they are manufactured without the addition of starter cultures, the microbiological safety of ready-to-eat sausages can be compromised. One of the posibillities of product standardisation is by appliying lactic acid bacteria (LAB) strains as starter cultures. Lactobacillus sakei is one of the most competitive LAB with natural microbiota of the meat. During this study, two strains of Lb sakei (MRS_296 and C_7d_13), previously isolated from sausages of this type and characterised in detail, were added to the sausage mixture.The survival of added starter cultures during fermentation and ripening of sausages was monitored, as well as their influence on the physico-chemical characteristics of sausages and the naturally present microbiota. Significantly lower pH was observed in inoculated sausages after 7 days (p <0.001) and 40 days (p <0.001) compared to the control (non inoculated) sausage. Correlation between the number of detected lactobacilli and the pH decrease in inoculated (r= -0.97, p<0.001) and control sausage (r= -0,81, p<0,05) was confirmed. Analysis of rep-PCR patterns showed that starter C_7d_13 did not survive and strain MRS_296 did survive during the processes of production, fermentation and ripening. Thatˊs why in inoculated sausage number of E. coli, coliform bacteria and S. aureus had fallen underneath the detection level. However, permitted number of enterobacteria is crossing the lines in inoculated and control sausage.

• Keywords: starter; Lactobacillus sakei; fermentirane kobasice; rep-PCR; sigurnost hrane
• Keywords (english): starter culture; Lactobacillus sakei; fermented sausages; rep-PCR; food safety
• Language: croatian
• URN:NBN: urn:nbn:hr:204:105021
• Study programme: Title: Agroecology; Study programme type: university; Study level: graduate; Academic / professional title: magistar/ magistra inženjer/inženjerka agroekologija (magistar/ magistra inženjer/inženjerka agroekologija)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-11-30 08:50:45