Leivajuuretistes sisalduvate mikroobide biokeemilised ja antagonistlikud omadused
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Kuupäev
2020
Kättesaadav alates
05.09.2020
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Eesti Maaülikool
Abstrakt
Leivajuuretise kasutamine leivatootmisel on oluline saavutamaks heade maitse-, lõhna- ja
tekstuuriomaduste ning toiteväärtusega pagaritooted. Kaasaegses leivatööstuses põhineb
leivajuuretise kasutamine selle igapäevasel värskendamisel, mille käigus segatakse leivateost
järelejäänud osa juuretisest värske jahu ja veega ning kääritatakse uueks leivajuuretiseks.
Regulaarne juuretise uuendamine aitab hoida juuretist ja selles leiduvaid mikroorganisme
metaboolselt aktiivsena ning seeläbi kindlustada juuretise käärimisvõime. Sellele vaatamata
võivad muutused juuretise fermentatsiooni parameetrites ja tooraine (nt. jahu) mikroobses
koostises põhjustada suuremaid muutusi leivajuuretise mikrobiootas ja selle stabiilsuses.
Sellest tulenevalt on kasvav trend kasutada kommertsiaalseid starterkultuure, mis
võimaldavad alustada või jätkata stabiilset leivajuuretise fermentatsiooniprotsessi. Kuna
osadel pagaritööstustel puudub teave leivajuuretise mikroobse koosluse ja stabiilsuse kohta,
on problemaatiline valida leivajuuretise fermentatsiooniks sobivaid starterkultuure. Seetõttu
on oluline kindlaks teha ja välja valida need mikroobitüved, mis annavad pagaritoodetele
iseloomuliku maitse- ja tekstuuriomadused.
Bakalaureusetöö eesmärk oli identifitseerida Eesti ühe pagaritööstuse leivajuuretiste
mikroobide kooslusi ning välja selgitada isoleeritud mikroobiliikide biokeemilised ja
antagonistlikud omadused. Selleks identifitseeriti API kit ja MALDI-TOF meetodite abil
kahest leivajuuretistest isoleeritud puhaskultuurid ning määrati piimhappebakterite
antagonistlikud omadused ja pärmseenete biokeemilisi omadused, kasutades selleks vastavalt
well-diffusion meetodit ja Vernier' digitaalseid andmekogujaid.
Uurimistöö tulemusena selgus, et leivajuuretistest eraldatud mikroobid kuulusid
perekondadesse Lactobacillus, Leuconostoc, Weisella, Saccharomyces, Kasahstania,
Metschnikowia, Torulaspora ja Bacillus. Suurema etanooli produktsiooniga pärmseene liigid
olid S. cerevisiae ja K. humilis ning süsinikdioksiidi tootmisvõime oli suurem pärmseentel S.
cerevisiae ja Metschnikowia spp. Samuti leiti, et uuritud piimhappebakteritel ei olnud
antagonistlikku toimet üksteise kasvu suhtes.
Sourdough fermentation is considered to play a key role to get improved flavor, texture and nutritional properties of bakery products. In the modern bakery industry, the use of sourdough bases on its daily refreshment process during which the remaining part of the sourdough is mixed with fresh flour and water and fermented into a new batch of sourdough. Regular refreshment procedure helps to keep the sourdough and its microbiota metabolically active and thereby to ensure the fermentation ability of the sourdough. However, alterations to the fermentation parameters or significant variations in the microbial composition of the flour can induce major changes in the sourdough microbiota. Therefore, it is growing trend to use commercially available starter cultures that enable to start or to continue stable sourdough fermentation process. Since some bakery industry don´t have information about the composition and the stability of their sourdough it is complicated to choose suitable cultures for their sourdough fermentation process. Because of this, it is necessary to identify and select out these microbial strains that give characteristic taste and texture properties to their bakery products. The aim of the Bachelor’s thesis was to identify microbe communities of sourdoughs in one Estonian bakery industry and to determine the biochemical and functional properties of isolated microbial species and their biochemical and antagonistic properties in sourdoughs. For this, pure cultures from two types of sourdough were identified by the API kit and MALDI-TOF methods. The antagonistic properties of lactic acid bacteria and biochemical properties of yeast were tested, using respectively the well-diffusion method and digital data capture system Vernier. As a result of the research, it was concluded that microbes isolated from sourdoughs belonged to the following genus: Lactobacillus, Leuconostoc, Weisella, Saccharomyces, Kazachstania, Metschnikowia, Torulaspora and Bacillus. The yeast species with higher ethanol production were S. cerevisiae and K. humilis and higher carbon dioxide amount were produced by S. cerevisiae and Metschnikowia spp. There was also found that the lactic acid bacteria studied did not have an antagonistic effect on the growth of other lactic acid bacteria.
Sourdough fermentation is considered to play a key role to get improved flavor, texture and nutritional properties of bakery products. In the modern bakery industry, the use of sourdough bases on its daily refreshment process during which the remaining part of the sourdough is mixed with fresh flour and water and fermented into a new batch of sourdough. Regular refreshment procedure helps to keep the sourdough and its microbiota metabolically active and thereby to ensure the fermentation ability of the sourdough. However, alterations to the fermentation parameters or significant variations in the microbial composition of the flour can induce major changes in the sourdough microbiota. Therefore, it is growing trend to use commercially available starter cultures that enable to start or to continue stable sourdough fermentation process. Since some bakery industry don´t have information about the composition and the stability of their sourdough it is complicated to choose suitable cultures for their sourdough fermentation process. Because of this, it is necessary to identify and select out these microbial strains that give characteristic taste and texture properties to their bakery products. The aim of the Bachelor’s thesis was to identify microbe communities of sourdoughs in one Estonian bakery industry and to determine the biochemical and functional properties of isolated microbial species and their biochemical and antagonistic properties in sourdoughs. For this, pure cultures from two types of sourdough were identified by the API kit and MALDI-TOF methods. The antagonistic properties of lactic acid bacteria and biochemical properties of yeast were tested, using respectively the well-diffusion method and digital data capture system Vernier. As a result of the research, it was concluded that microbes isolated from sourdoughs belonged to the following genus: Lactobacillus, Leuconostoc, Weisella, Saccharomyces, Kazachstania, Metschnikowia, Torulaspora and Bacillus. The yeast species with higher ethanol production were S. cerevisiae and K. humilis and higher carbon dioxide amount were produced by S. cerevisiae and Metschnikowia spp. There was also found that the lactic acid bacteria studied did not have an antagonistic effect on the growth of other lactic acid bacteria.
Kirjeldus
Bakalaureusetöö
Toiduainete tehnoloogia õppekaval
Märksõnad
bakalaureusetööd, leivajuuretis, mikrofloora, antagonism, fermentatsioon