Õlleraba säilitamise meetodid ja nende mõju mikroobide arvukusele
Laen...
Kuupäev
2022
Kättesaadav alates
10.09.2022
Autorid
Koppel, Emeri
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Eesti Maaülikool
Abstrakt
Õlu on maailmas väga populaarne jook, kuid selle tootmisprotsessis tekib suurel hulgal
kõrvalsaadust, mida nimetatakse õllerabaks. Enamasti suunatase õlle tegemisel tekkiv
õlleraba loomasöödaks või visatakse ära. Kuid oma toiteväärtuse tõttu on õlleraba siiski
väga huvipakkuv toore, millega saaks rikastada ka inimestele mõeldud toite.
Bakalaureusetöö eesmärk oli anda ülevaade õlleraba mikrobioloogilisest koostisest ja
selgitada, millised tegurid seda mõjutada võivad ning kuidas säilib õlleraba värskelt,
kuivatatult ning sügavkülmutatult. Töö käigus määrati bakterite üldarv värskes õllerabas
ning selle säilitamisel 2 ja 4 tundi temperatuuridel 5 °C, 20 °C ja 30 °C. Lisaks säilitati
õlleraba kuni 28 päeva kuivatatult ja sügavkülmutatult ning määrati bakterite üldarv iga
7 päeva järel. Töö käigus määrati ka kuivaine kogus värskes õllerabas ning kuivatatud
õlleraba kuivainest analüüsiti selle keemilist koostist (toorproteiin, -kuid, -rasv ja suhkrute
sisaldus).
Käesolevas bakalaureusetöös jäi värskes õllerabas bakterite üldarv vahemikku
3,7x102
kuni 9,6x103
pmü/g, olles keskmiselt 4,5x10
3
pmü/g. Õlleraba lühiajalisel
säilitamisel saadud tulemused näitavad, et värskes õllerabas, mida hoiti temperatuuril
5 °C, toimus esimesel kahel tunnil mikroobide hulgas langus kuid 4 tunni pärast oli
mikroobide arvukus pisut tõusnud, ehkki see muutus ei olnud statistiliselt oluline (p>0,05).
Õlleraba säilitamisel temperatuuril 20 °C kuni neli tundi, mikroobide hulk oluliselt ei
muutunud (p>0,05). Mikroobide kasvu märgatavaim muutus õllerabas esines kahe tunni
möödudes, mida hoiti temperatuuril 30 °C – 3,9x102
- 1,4x104
pmü/g, kuid statistiliselt
polnud selline mikroobide kasvu tõus oluline (p>0,05) ning neli tundi hiljem oli
mikroobide üldarv 1,0x103
- 9,1x103
pmü/g. Kuivatatud õllerabas mikroobide hulk
28 päevasel säilitamisel küll kõikus, kuid statistiliselt ei olnud selles suuri erinevusi
(p>0,05). Külmutatud õlleraba proovides oli 7. säilitamise päevaks toimunud mikroobide
arvukuses järsk ning statistiliselt oluline langus (tasemele 1,3x103
pmü/g, p<0,05), mis
metoodikast tulenevalt 14. päevaks statistiliselt oluliselt taas tõusis (1,6x104
pmü/g,
p<0,05). Õlleraba kuivatatult versus külmutatult säilitamisel statistiliselt olulisi erinevusi
ei tuvastatud (p<0,05). Õlleraba kuivaine, toorproteiini ja toorrasva ning suhkrute
sisalduse tulemused sarnanevad kirjanduses esitatud andmetele.
Edaspidiselt tuleks uurida, kui pikaajaliselt saaks värsket õlleraba säilitada pruulikoja
tingimustes ning kas õlleraba kuivatatult või külmutatult säilitamisel on mõjusid ka selle
keemilisele koostisele.
Beer is a very popular drink in the world, but its production produces a large number of by-products called brewer’s spent grain (BSG). In most of the cases the BSG in beer production is directed to animal feed or is discarded. However, due to its nutritional value BSG is a very interesting raw material that can be used to enrich food for humans. The aim of the bachelor's thesis was to give an overview of the microbiological composition of the BSG, the factors that may affect it and to study how the BSG is preserved fresh, dried and frozen. The task of the work was to determine the total number of bacteria in a fresh BSG and during its storage for 2 and 4 hours at 5 °C, 20 °C and 30 °C. In addition, the BSG was stored dried and frozen for up to 28 days and the total bacterial count was determined in every 7 days. The dry matter content of the BSG was also determined and the dry matter of the BSG was analyzed for its chemical composition (crude protein, fiber, fat and sugar content) in this study. In this bachelor's thesis, the total number of bacteria in the fresh BSG ranged from 3.7x102 to 9.6x103 cfu/g, averaging at 4.5x103 cfu/g. The results obtained during the short-term storage of the BSG show that in the fresh BSG, which was kept at 5 °C, there was a decrease in the number of microbes after the first two hours but after 4 hours the number of microbes slightly increased, yet this change was not statistically significant (p>0.05). When the BSG was stored at 20 ° C for up to four hours, the number of microbes did not significantly change (p>0.05). The most noticeable change in microbial growth was observed after two hours at 30 ° C – 3.9x102 - 1.4x104 cfu/g, but this increase in microbial growth was not statistically significant (p>0.05) and four hours later the total number of microbes was 1.0x103 - 9.1x10³ cfu/g. The number of microbes in the dried BSG fluctuated after 28 days of storage, but there were no statistically significant differences (p>0.05). In the samples of the frozen BSG, there was a sharp and statistically significant decrease in the number of microbes by the 7th day of storage (1.3x103 cfu/g, p<0.05), which increased again significantly by the 14th day (1.6x104 cfu/g, p<0.05) due to the methodology. There were no statistically significant differences (p<0.05) between drying or freezing the BSG. The results for the dry matter, crude protein and crude fat and sugars of the BSG were similar to those that are reported in the literature. In the future, it should be investigated of how long a fresh brewer’s spent grain can be stored in the brewery's conditions and whether BSG stored dried or frozen has also an effect on its chemical composition.
Beer is a very popular drink in the world, but its production produces a large number of by-products called brewer’s spent grain (BSG). In most of the cases the BSG in beer production is directed to animal feed or is discarded. However, due to its nutritional value BSG is a very interesting raw material that can be used to enrich food for humans. The aim of the bachelor's thesis was to give an overview of the microbiological composition of the BSG, the factors that may affect it and to study how the BSG is preserved fresh, dried and frozen. The task of the work was to determine the total number of bacteria in a fresh BSG and during its storage for 2 and 4 hours at 5 °C, 20 °C and 30 °C. In addition, the BSG was stored dried and frozen for up to 28 days and the total bacterial count was determined in every 7 days. The dry matter content of the BSG was also determined and the dry matter of the BSG was analyzed for its chemical composition (crude protein, fiber, fat and sugar content) in this study. In this bachelor's thesis, the total number of bacteria in the fresh BSG ranged from 3.7x102 to 9.6x103 cfu/g, averaging at 4.5x103 cfu/g. The results obtained during the short-term storage of the BSG show that in the fresh BSG, which was kept at 5 °C, there was a decrease in the number of microbes after the first two hours but after 4 hours the number of microbes slightly increased, yet this change was not statistically significant (p>0.05). When the BSG was stored at 20 ° C for up to four hours, the number of microbes did not significantly change (p>0.05). The most noticeable change in microbial growth was observed after two hours at 30 ° C – 3.9x102 - 1.4x104 cfu/g, but this increase in microbial growth was not statistically significant (p>0.05) and four hours later the total number of microbes was 1.0x103 - 9.1x10³ cfu/g. The number of microbes in the dried BSG fluctuated after 28 days of storage, but there were no statistically significant differences (p>0.05). In the samples of the frozen BSG, there was a sharp and statistically significant decrease in the number of microbes by the 7th day of storage (1.3x103 cfu/g, p<0.05), which increased again significantly by the 14th day (1.6x104 cfu/g, p<0.05) due to the methodology. There were no statistically significant differences (p<0.05) between drying or freezing the BSG. The results for the dry matter, crude protein and crude fat and sugars of the BSG were similar to those that are reported in the literature. In the future, it should be investigated of how long a fresh brewer’s spent grain can be stored in the brewery's conditions and whether BSG stored dried or frozen has also an effect on its chemical composition.
Kirjeldus
Bakalaureusetöö
Toiduainete tehnoloogia õppekaval
Märksõnad
bakalaureusetööd, õlleraba mikrobioloogia, õlleraba säilitamine, õlleraba keemiline koostis