Karakterizacija mikrobiote prirodno fermentisane pirotske "peglane" kobasice tokom zrenja i gotovog proizvoda
Characterization of the Microbiota of Naturally Fermented Pirot “Ironed” Sausage During Maturation and the Finished Product
Докторанд
Bogdanović, SvetlanaМентор
Stanković, SlavišaЧланови комисије
Dimkić, IvicaBerić, Tanja
Medić, Olja
Vesković-Moračanin, Slavica
Метаподаци
Приказ свих података о дисертацијиСажетак
Pirotska „peglana“ kobasica je tradicionalna, fermentisana kobasica, koja se pravi od različitih
vrsta mesa, soli i začina, a bez dodatka starter kultura. Testirani su uzorci kobasica šest proizvođača
od kojih su neki koristili standardnu a neki nestandardnu recepturu. Ukupni diverzitet bakterija je
ispitivan u gotovom proizvodu i tokom zrenja u različitim vremenskim tačkama korišćenjem
odgajivačkog i neodgajivačkog (sekvenciranje gena za 16S rRNK) pristupa. Genetički polimorfizam
predstavnika različitih grupa bakterijskih izolata određivan je korišćenjem rep-PCR i RAPD-PCR
tehnika sa specijalizovanim prajmerima. Rezultati identifikacije sekvenciranjem gena za 16S rRNK
ukazuju na prisustvo samo dve vrste bakterija mlečne kiseline, Lactobacillus sakei (76%) i
Leuconostoc mesenteroides (24%). U poređenju sa drugim prajmerima, najveću diskriminatornu moć
pokazao je prajmer GTG5, kod većine testiranih izolata. Sekvenciranjem naredne generacije utvrđena
je dominacija predstavnika iz razdela... Proteobacteria i Firmicutes u svim proučavanim uzorcima.
Tokom procesa zrenja uočen je trend povećanja zastupljenosti predstavnika Firmicutes (sa 33,5% na
63,5%) i smanjenje udela Proteobacteria (sa 65,4% na 22,3%). Metabarkoding analiza je pokazala
da su dominantni bakterijski rodovi tokom procesa zrenja kobasice bili: Lactobacillus,
Photobacterium, Leuconostoc, Weissella i Lactococcus, dok su detektovani i Carnobacterium,
Brochothrix i Acinetobacter. Odgajivačkim pristupom je utvrđeno prisustvo vrsta Lactobacillus sakei
i Leuconostoc mesenteoides u svim fazama zrenja. Upoređen je sastav bakterijskih zajednica u
gotovom proizvodu svakog testiranog proizvođača. U uzorcima PK1 i PK2 pokazano je najveće
bogatstvo bakterijskih vrsta. Predstavnici razdela Firmicutes su bili dominantni u uzorcima PK3,
PK4, PK5 i PK6, dok su predstavnici Proteobacteria bili najzastupljeniji u uzorcima PK1 i PK2. U
zavisnosti od uzorka, dominiraju vrste roda Lactobacillus, L. sakei i L. algidus, dok je rod
Leuconostoc nađen u svim uzorcima. U gotovom proizvodu i tokom zrenja u različitim vremenskim
tačkama određivane su i fizičko-hemijske osobine kobasice. Primećeno je smanjenje pH vrednosti,
aktivnosti vode i sadržaja vlage, i povećanje sadržaja proteina i masti. Različite recepture i različito
vreme zrenja pirotske “peglane” kobasice nisu imale značajan uticaj na profil masnih kiselina, ali su
imale značajan efekat na instrumentalne parametre boje. Takođe, zabeležene su i statistički značajne
razlike ispitivanih parametara teksture između kobasica proizvedenih po različitim recepturama.
Različiti udeli upotrebljenog mesa prouzrokovali su značajne razlike u pogledu senzornih
karakteristika.
Pirot "ironed" sausage is a traditional fermented sausage made from various meats, salt, and
spices, without the addition of starter cultures. Sausage samples from six producers were studied,
some of which used standard and some non-standard recipes. Total bacterial diversity was studied in
the finished product and during ripening at different time points using cultivating and non-cultivating
methods. Genetic polymorphism of representatives of different groups of bacterial isolates was
determined using rep-PCR and RAPD-PCR techniques with specific primers. The results of 16S
rRNA gene sequencing indicated the presence of only two species of lactic acid bacteria,
Lactobacillus sakei (76%) and Leuconostoc mesenteroides (24%). Compared to other primers, the
GTG5 primer showed the highest discriminatory power for most of the isolates tested. Next generation
sequencing showed that representatives of Proteobacteria and Firmicutes dominated in all samples
tested. During maturation, a trend of... increasing the proportion of Firmicutes representatives (from
33.5% to 63.5%) and decreasing the proportion of Proteobacteria (from 65.4% to 22.3%) was
observed. Metabarcoding analysis showed that the dominant bacterial genera during the sausage
ripening process were the following: Lactobacillus, Photobacterium, Leuconostoc, Weissella and
Lactococcus, while Carnobacterium, Brochothrix and Acinetobacter were also detected. The
presence of the species Lactobacillus sakei and Leuconostoc mesenteoides at all stages of maturation
was detected in the cultivation approach. The composition of bacterial communities in the final
product of each tested producer was compared. Samples PK1 and PK2 showed the highest abundance
of bacterial species. Representatives of the Firmicutes dominated in samples PK3, PK4, PK5 and
PK6, while representatives of Proteobacteria were most abundant in samples PK1 and PK2.
Depending on the sample, species of the genus Lactobacillus, L. sakei and L. algidus dominated,
while the genus Leuconostoc was found in all samples. The physical and chemical properties of the
sausage were also determined in the finished product and during ripening at different times. Decreases
in pH, water activity, and moisture content were found, as well as increases in protein and fat content.
Different recipes and different ripening times of Pirot "ironed" sausage had no significant effect on
the fatty acid profile, but a significant effect on the instrumental color parameters. Statistically
significant differences were also found in the investigated texture parameters between sausages
produced according to different recipes. Different proportions of meat used resulted in significant
differences in sensory properties.