Effect of essential oils on survival of salmonella spp. in pork packaged in vacuum and modified atmosphere

Despite efforts and improvements in slaughter hygiene and food production techniques in the food industry, foodborne pathogens including Salmonella spp as one of the most often pathogen found in meat, still cause millions of episodes of illness annually worldwide, presenting not only health but also an economic problem in both developed and developing countries. Salmonella Enteritidis and Salmonella Typhimurium are serotypes mainly reported as causes of human salmonellosis, but outbreaks of salmonellosis caused by a rarer subspecies of Salmonella are increasing, which is why their control is needed. Eggs and poultry meat are still recognized as main sources of Salmonella infection in humans but salmonellosis caused by consuming contaminated pork meat and derived products are increasing. Moreover, the meat industry is challenged by the new trend of producing all-natural food, where is no place for artificial preservatives which may have some carcinogenic and toxic properties or may cause food allergies or sensitivities. Essential oils (EOs) are plants derived which gained attention mainly due to its antibacterial and antioxidative properties, and potential to be used as a replace for synthetic additives in the food industry. EOs can reduce the incidence of food-borne diseases, extend shelf-life and retard lipid oxidation. Thyme and oregano EO are one of the top ten EOs used as a preservative for food purposes. The aim of this PhD thesis was to evaluate the effect of different packaging conditions (vacuum and modified atmosphere) and different concentrations (0.3%, 0.6% and 0.9%) of thyme and oregano essential oils on survival of Salmonella spp., microbiological status of pork meat, as well as antioxidative properties if essential oils and their effect on lipid oxidation in meat, physicochemical parameters and organoleptic acceptability of meat. Meat used in present study was obtained from pork muscles from legs of different animals, crossbreeds Yorkshire x Landrace and minced in a grinder with 4 mm perforations in the grinding plates. At the beginning of the experiment chemical composition of EOs was determined (GC-MS analysis), as well as antioxidative capacity of EOs (DPPH test, nitric oxide and hydroxyl-radical scavenger capacity, FRAP assay, lipid peroxidation) and minimal inhibitory concentration (MIC) of EOs and active compounds e.g. thymol, carvacrol, eugenol and cinnamaldehyde (microdilution method) needed to inhibit the grow of six serotypes of Salmonella spp. (S. Enteritidis, S. Typhimurium, S. Infantis, S. Montevideo, S. Senftenberg, S. Givae) and the four-strain cocktail of Salmonella chosen to be used in meat contamination (S. Enteritidis, S. Typhimurium, S. Infantis, S. Montevideo)... I pored uloženih napora i dostignuća koja su ostvarena u prehrambenoj industriji na polju higijene klanja i proizvodne prakse, bakterije uzročnici bolesti prenosivih hranom u koje spada i Salmonella spp. kao jedan od najčešćih patogenih bakterija izolovanih iz mesa, i dalje uzrokuju milione slučajeva oboljenja godišnje na globalnom nivou, predstavljajući ne samo zdravstveni već i ekonomski problem, kako u razvijenim zemljama tako i zemljama u razvoju. Salmonella Enteritidis i Salmonella Typhimurium su serotipovi koji najčešće izazivaju salmonelozu ljudi, međutim sve se češće prijavljuju sliučajevi salmoneloze uzrokovane manje poznatim serotipovima, što naglašava potrebu za njihovom kontrolom. Iako se jaja i meso živine i dalje smatraju glavnim izvorom Salmonella spp., salmoneloza uzrokovana konzumiranjem kontaminiranog svinjskog mesa i proizvoda od svinjskog mesa je u porastu. Industrija mesa se suoči sa novim trendom organske proizvodnje, gde nema mesta za primenu do sada korišćenih hemijskih konzervanasa, od kojih neki ispoljavaju kancerogene i toksične osobine ili dovode do pojava alergija. Etarska ulja su biljni ekstrakti koji se izučavaju pre svega zbog antibakterijskih i antioksidativnih osobina ali i mogućnosti da se koriste kao zamena za sintetičke aditive u prehrambenoj industriji. Primena etarskih ulja može da smanji incidenciju bolesti prenosivih hranom, da produži održivost namirnica i odloži lipidnu oksidaciju. Etarsko ulje timijana i origana jedni su od deset najčešće korišćenih etarskih ulja za primenu u hrani. Cilj istraživanja u okviru ove doktorske disertacije bio je ispitivanje različitih načina pakovanja (vakuum i modifikovana atmosfera) i antimikrobnog efekta različitih koncentracija etarskih ulja origana i timijana (0,3%, 0,6% i 0,9%), na Salmonella spp. i mikrobiološki status mesa, kao i ispitivanje antioksidativnih osobina pomenutih etarskih ulja i njihovog efekta na oksidativne promene lipidne frakcije, fizičko hemijske osobine i prihvatljivost mlevenog svinjskog mesa. Kao sirovina za ispitivanje korišćeno je mleveno meso mišića buta svinja meleza Jorkšira x Landrasa. Na početku eksperimenta ispitan je hemijski sastav etarskih ulja (GC-MS), antioksidanti potencijal etarskih ulja (DPPH test, kapacitet neutralizacije •OH i NO• radikala FRAP test, lipidna peroksidacija) i minimalna inhibitorna koncentracija etarskih ulja timijana i origana, ali i aktivnih principa, eugenola, timola, karvakrola i cinamaldehida (mikrodiluciona metoda) potrebna za inhibiciju šest serovarijeteta Salmonella spp. (S. Enteritidis, S. Typhimurium, S. Infantis, S. Montevideo, S. Senftenberg, S. Givae) i koktel serovarijeteta odabranog za kontaminaciju mesa (S. Enteritidis, S. Typhimurium, S. Infantis, S. Montevideo)...