Usporedba fermentacijskih karakteristika dvaju sojeva pivskog kvasca na sladovini s različitim udjelima ekstrakta

master's thesis

• Title (english): Comparison of fermentation characteristics of two brewer's yeast in wort with different gravity
• Author: Dijana Petrić
• Mentor: Mirela Ivančić - Šantek (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Biochemical Engineering); (Laboratory for Biochemical Engineering, Industrial Microbiology and Malting and Brewing Technology); Zagreb
• Defense date and country: 2013-09-27, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Biotechnology

Abstract

Postupak proizvodnje piva sa sladovinom s visokim udjelom ekstrakta postao je atraktivna alternativa tradicijskom postupku proizvodnje zbog ekonomske isplativosti i kvalitete proizvedenog piva. Međutim većina pivskih kvasaca u sladovini s visokim udjelom ekstrakta raste slabije, fermentacije su spore i zaostaju neprevreli fermentabilni ugljikohidrati. U ovom radu proučavane su fermentacijske karakteristike dva soja pivskog kvasca, 12-2 i WT tijekom fermentacije sladovine s različitim sadržajem ekstrakta. Soj 12-2 dobiven evolucijskim inženjerstvom iz roditeljskog soja WT koji se koristi u komercijalnoj proizvodnji lager piva. Tijekom fermentacije sladovine s 25 % ekstrakta soj 12-2 je brže fermentirao fermentabilne ugljikohidrate, postigao veći stupanj prevrenja sladovine i povećao prinos etanola. Soj 12-2 brže je fermentirao sladovinu s 18 % ekstrakta i proizveo 1,74 % (vol/vol) etanola više u odnosu na soj WT. Produženom aeracijom sladovine s vrlo visokim udjelom ekstrakta tijekom fermentacije sa sojem 12-2 postignut je veći stupanj prevrenja. Količina utrošenog slodobnog amino dušika se smanjivala s povećanjem sadržajem ekstrakta u sladovini.

Abstract (english)

High gravity brewing has become an attractive alternative to traditional brewing methods due to a number of economic and product quality advantages. However many brewer's strains exhibit decreased growth, slow and incomplete fermentations. Here we studied fermentation characteristics of two brewer’s yeast strains, 12-2 and WT during cultivation with different wort gravity. Strain 12-2 was designed using evolutionary engineering from the parent strain WT which is used in commercial production of lager beer. Strain 12-2 showed higher fermentation rate of fermentable sugars, increased attenuation and increased ethanol yield during fermentation of very high gravity wort in bioreactor. Furthermore, strain 12-2 fermented faster high-gravity wort and produced 1,74 % (vol/vol) more ethanol compare to WT strain. Better attenuation of very high gravity wort was achieved by prolonged aeration of media during fermentation with strain 12-2. The amount of assimilated free amino nitrogen decreased with increase of the wort gravity.

• Keywords: sladovina s vrlo visokim udjelom ekstrakta; pivo; pivski kvasac; kisik; fermentacija
• Keywords (english): very high-gravity wort; beer; brewer's yeast; oxygen; fermentation
• Language: croatian
• URN:NBN: urn:nbn:hr:159:693819
• Study programme: Title: Bioprocess Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka bioprocesnog inženjerstva (magistar/magistra inženjer/inženjerka bioprocesnog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2017-05-04 12:42:31