Selection of Lactobacillus strains as starter cultures for the Production of fermented sausages

Prilikom industrijske proizvodnje fermentiranih proizvoda, starter kulture su često izložene nepovoljnim uvjetima, specifičnim za tehnološki proces proizvodnje, poput visokih koncentracija soli, promjena pH vrijednosti i temperature i dostupnosti kisika. Prilikom odabira funkcionalnih starter kultura važno ispitati osjetljivost odabranih sojeva na navedene uvjete. Stoga je u ovom radu ispitan rast autohtonih Lactobacillus sojeva u MRS tekućoj hranjivoj podlozi s različitim koncentracijama NaCl (1,6 %, 5 %, 10 % i 15 %). Također, je ispitan i rast autohtonih sojeva u tekućoj MRS podlozi, kojoj je podešena pH vrijednosti u kiselom i alkalnom području. Uspješan rast i sinteza mliječne kiseline tijekom fermentacije su ključne karakteristike Lactobacillus sojeva koji omogućuju mikrobiološku i senzoričku kvalitetu krajnjeg proizvoda. Također je ispitan rast autohtonih Lactobacillus sojeva tijekom fermentacije i mogućnost sinteze mliječne kiseline, što su važna tehnološka svojstva funkcionalnih starter kultura. Na temelju ispitanih kriterija koji su važni prilikom odabira funkcionalnih starter kultura, od 50 autohtonih izolata bakterija mliječne kiseline iz roda Lactobacillus, odabrani su sojevi Lb. fermentum 10, Lb. brevis 19, Lb. fermentum 23 i Lb. curvatus 30 koji najuspješnije podnose visoke koncentracije soli i nepovoljne pH vrijednosti u MRS tekućoj podlozi, te proizvode visoke koncentracije mliječne kiseline.During the industrial production of different fermented products, starter cultures are often exposed to various stress conditions which are specific for the technological production, such as the high salt concentrations, changes in pH tolerance and temperature, availability of oxygen. During the evaluation of the functional starter culture there is a need to investigate the susceptibility of the selected strains to the specific stress conditions present during fermentations. Thus, it is important to examine how the selected strains survive in these conditions. So, the growth of the selected lactobacilli was tested at different NaCl concentrations (1,6 %, 5 %, 10% and 15 %) added to MRS broth medium. The growth of the autochthonous strains was also tested in MRS broth medium, with adjusted pH ranging from acidic to alkaline values. Effective growth and high acidification activity during fermentation are key characteristics of starter lactobacilli to ensure microbiological safety and sensory quality of the product. Also the growth of the indigenous Lactobacillus strains was tested during fermentation and the possibility of producing lactic acid, which are important technologic properties of functional starter cultures. Based on the examined criteria which are important during the selection of functional starter cultures, out of 50 indigenous lactic acid bacteria isolates of the genus Lactobacillus, the selected strains Lb. fermentum 10, Lb. brevis 19, Lb. fermentum 23 and Lb. curvatus 30 were the ones with the highest salt concentration tolerance and a high tolerance to adverse pH values in MRS medium, also they produced large quantities of lactic aci