Mikroobide elulemuse hindamine lüofiliseeritud tatraleivajuuretistes
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Kuupäev
2021
Kättesaadav alates
04.09.2021
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Eesti Maaülikool
Abstrakt
Traditsioonilisel meetodil valmistatud leivajuuretise kasutamine leiva tootmiseks on keerukas ja aeganõudev protsess, kuna juuretise metaboolselt aktiivsena hoidmine eeldab pidevat juuretise uuendamist. Sellest tulenevalt on väiketootjatel tarbijatele aktiivse leivajuuretise turustamine raskendatud. Lahendusena nähakse leivajuuretise kuivatamist, mis aitab tagada mikroobikultuuride stabiilsust nende pikaajalisel säilitamisel. Samas võib kuivatamine negatiivselt mõjuda mikroobide elulemusele ja tehnoloogilistele omadustele. Vaatamata laiapõhjalistele teadusuuringutele on mikroobide elujõu parendamine ja säilitamine endiselt suureks väljakutseks. Kommertsiaalsed kuivjuuretised saadakse juuretise kuivatamisel kõrgetel temperatuuridel, mistõttu ei jää sellise töötluse käigus mikroorganismid elama. Alternatiivne kuivatusmeetod leivajuuretise pikemaajaliseks säilitamiseks on külmkuivatamine, kuid vähe on kirjeldatud selle meetodi mõju juuretises leiduvatele mikroobidele.
Bakalaureusetöö eesmärk oli nii teaduskirjanduse kui ka eksperimentaalse töö alusel anda ülevaade tatraleivajuuretistes esinevatest mikroobidest ning tuvastada lüofiliseerimise ja krüoprotektantide mõju mikroobide elulemusele lüofiliseeritud tatraleivajuuretistes.
Töö raames teostati mikrobioloogilised ja füüsikalis-keemilised analüüsid käsitöönduslikust tatraleivajuuretisest ning lisa starterkultuure (Lactobacillus fermentum, Leuconostoc mesenteroides) sisaldavatest tatraleivajuuretistest. Fermenteeritud tatraleivajuuretiste lüofiliseerimisel kasutati kahe krüoprotektandi kombinatsiooni, millest ühel on tuvastatud kaitsev toime piimhappebakteritele ja teisel pärmseentele. Mikrobioloogilised analüüsid teostati juuretistest lüofiliseerimisjärgselt ja lüofiliseeritud juuretistest, mida oli säilitatud üks kuu kahel erineval säilitustemperatuuril (+4 °C ja +25 °C). Tuvastamaks, kas krüoprotektante ja starterkultuure sisaldaval tatraleivajuuretistel on mõju tatraleiva omadustele, viidi läbi tatraleibade sensoorne analüüs.
Bakalaureusetöö tulemusena selgus, et tatraleivajuuretiste mikroobses koosluses esines peamiselt Lactobacillus ja Saccharomyces perekonda kuuluvaid mikroobe. Piimhappebakterite ja pärmseente elulemus säilis paremini juuretistes, mille lüofiliseerimisel kasutati krüoprotektiivseid aineid. Krüoprotektantidest tagas kõrgema kaitse mikroobide elulemusele trehaloosi ja sahharoosi kombinatsioon. Lisatud starterkultuurid ja krüoprotektiivsed ained ei avaldanud mõju tatraleibade sensoorsetele omadusetele.
Traditional method of sourdough production for bread manufacturing is a complex and time-consuming process, as keeping the sourdough metabolically active requires constant back-slopping of the sourdough. As a result, it is complicated for small bussinesses to market active sourdough. The solution is to dry sourdough which helps to ensure the stability of microbial cultures during their long-term storage. However drying can adversely affect the viability and technological properties of microbes. Despite extensive research to improve and maintain microbial viability, there are major challenges. Commercial dry sourdoughs are obtained by drying the sourdough at a high temperature that does not contain such treatment for microorganisms to live. An alternative drying method for long-term storage of sourdough is freeze-drying but little information is available about how it affects the microbial survival. The aim of the Bachelor's thesis was to provide an overview of the microbes present in buckwheat sourdough and to identify the effect of lyophilization and cryoprotectants on the microbial survival in lyophilized buckwheat sourdough on the basis of both scientific literature and experimental work. Microbiological and physico-chemical analyzes were performed on artisanal buckwheat sourdoughs and buckwheat sourdoughs containing additional starter cultures (Lactobacillus fermentum, Leuconostoc mesenteroides). A combination of two cryoprotectants was used to lyophilize the fermented buckwheat sourdoughs, one of which has been shown to have a protective effect on lactic acid bacteria and the other on yeasts. Microbiological analyzes were performed on sourdoughs after lyophilization and on lyophilized sourdoughs stored for one month at two different storage temperatures (+4 °C and +25 °C). Sensory analysis of buckwheat breads were performed to determine whether buckwheat sourdough containing cryoprotectants and starter cultures have an effect on buckwheat bread properties. As a result of the Bachelor's thesis, it became clear that the microbial community of buckwheat sourdoughs contained mainly microbes belonging to the families Lactobacillus and Saccharomyces. The survival of lactic acid bacteria and yeasts was better preserved in sourdough lyophilized using cryoprotective agents. Of the cryoprotectants, the combination of trehalose and sucrose provided higher protection for microbial survival. The added starter cultures and cryoprotective agents did not affect the sensory properties of buckwheat breads.
Traditional method of sourdough production for bread manufacturing is a complex and time-consuming process, as keeping the sourdough metabolically active requires constant back-slopping of the sourdough. As a result, it is complicated for small bussinesses to market active sourdough. The solution is to dry sourdough which helps to ensure the stability of microbial cultures during their long-term storage. However drying can adversely affect the viability and technological properties of microbes. Despite extensive research to improve and maintain microbial viability, there are major challenges. Commercial dry sourdoughs are obtained by drying the sourdough at a high temperature that does not contain such treatment for microorganisms to live. An alternative drying method for long-term storage of sourdough is freeze-drying but little information is available about how it affects the microbial survival. The aim of the Bachelor's thesis was to provide an overview of the microbes present in buckwheat sourdough and to identify the effect of lyophilization and cryoprotectants on the microbial survival in lyophilized buckwheat sourdough on the basis of both scientific literature and experimental work. Microbiological and physico-chemical analyzes were performed on artisanal buckwheat sourdoughs and buckwheat sourdoughs containing additional starter cultures (Lactobacillus fermentum, Leuconostoc mesenteroides). A combination of two cryoprotectants was used to lyophilize the fermented buckwheat sourdoughs, one of which has been shown to have a protective effect on lactic acid bacteria and the other on yeasts. Microbiological analyzes were performed on sourdoughs after lyophilization and on lyophilized sourdoughs stored for one month at two different storage temperatures (+4 °C and +25 °C). Sensory analysis of buckwheat breads were performed to determine whether buckwheat sourdough containing cryoprotectants and starter cultures have an effect on buckwheat bread properties. As a result of the Bachelor's thesis, it became clear that the microbial community of buckwheat sourdoughs contained mainly microbes belonging to the families Lactobacillus and Saccharomyces. The survival of lactic acid bacteria and yeasts was better preserved in sourdough lyophilized using cryoprotective agents. Of the cryoprotectants, the combination of trehalose and sucrose provided higher protection for microbial survival. The added starter cultures and cryoprotective agents did not affect the sensory properties of buckwheat breads.
Kirjeldus
Bakalaureusetöö
Toiduainete tehnoloogia õppekaval
Märksõnad
bakalaureusetööd, tatraleivajuuretis, fermentatsioon, starterkultuurid, külmkuivatamine, krüoprotektandid