Mikrobiološki i fizikalno – kemijski profil hrvatskih piva

master's thesis

• Title (english): Microbiological and physico-chemical profiling of Croatian beer
• Author: Ana Gukov
• Mentor: Božidar Šantek (mentor)
• Committee member: Blaženka Kos (predsjednik povjerenstva)
• 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: 2021-03-01, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Biotechnology

Abstract

U ovom radu provedene su mikrobiološke i fizikalno–kemijske analize 11 različitih vrsta piva. Mikrobiološkim ispitivanjima pronađeni su aerobni i anaerobni mikroorganizmi u svim uzorcima piva. U komercijalno dostupnim vrstama piva potvrđen je rast aerobnih i anaerobnih bakterija koje proizvode organske kiseline. U nekim je pivima potvrđeno prisustvo radnog kvasca. U niti jednom pivu nisu pronađene koliformne bakterije ili kvasci iz roda Brettanomyces. U dva uzorka piva dokazana je prisutnost bakterija koje zagađuju pivo: Lactobacillus brevis, Lactobacillus lindneri i Pediococcus damnosus. U niti jednom od 11 uzoraka piva nisu pronađene vrste Acetobacter pasterianus i Lactobacillus acidophilus. U jednom je uzorku piva dokazana prisutnost kvasca Saccharomyces cerevisiae var. diastaticus koji se smatra kvascem koji kvari pivo. Dokazani mikroorganizmi nisu znak zdravstvene neispravnosti piva, već utječu na organoleptičke promjene, mogu uzrokovati mutnoću i talog, te promjenu okusa piva. Fizikalno–kemijske analize pokazale su da su ispitivani parametri, pH i boja piva, bili u skladu s propisima. pH je u rasponu 4,18 – 4,89. Boja piva je za svijetla piva do 30 EBC (engl. European brewery convention), za tamna piva oko 57 EBC, za rezano lager pivo 49 EBC. Do odstupanja je došlo kod 3 uzorka, koji su imali veće EBC vrijednosti od očekivanih za pojedinu vrstu piva. Mjerena je i gorčina piva 6 mjeseci nakon otvaranja piva te su vrijednosti gorčine bile gotovo 10 puta manje od literaturno očekivanih u svim uzorcima. Gorčina je izražena u IBU (engl. International Bitterness Units) jedinicama, a uzrok odstupanja je proces starenja piva.

Abstract (english)

In this study, microbiological and physico–chemical analysis of 11 different beers were performed. Aerobic and anaerobic microorganisms were detected in all beer samples. All commercial beers contained aerobic and anaerobic, organic acid - producing bacteria. In some samples brewing yeasts were found. No samples contained coliform bacteria or Brettanomyces yeasts. Two beer samples contained typical beer spoilage bacteria: Lactobacillus brevis, Lactobacillus lindneri and Pediococcus damnosus. None of the beer samples contained Acetobacter pasterianus and Lactobacillus acidophilus species. In one beer sample, it was found Saccharomyces cerevisiae var. diastaticus, the beer-spoiling yeast. Microorganisms found in some of the samples are not human pathogens and do not pose health threat, but they can affect organoleptic properties, cause increased turbidity and sedimentation, and change beer taste. Physico–chemical analysis included pH, colour and bitterness measurements. pH and colour were within the law regulated limit, pH between 4.18 - 4.89, and the colour of light beer up to 30 EBC (European brewery convention), for dark beer about 57 EBC, for half-half beer 49 EBC. Three beer samples had higher EBC values than it would be expected for that type of beer. The bitterness was measured 6 months after the beer was opened, hence the values were almost 10 times less than expected, perhaps due to beer aging. Bitterness was expressed as IBU (International Bitterness Units).

• Keywords: mikrobiologija piva; PCR; pivo; fizikalno-kemijske analize; kvasac
• Keywords (english): beer microbiology; PCR; beer; physico – chemical analysis; yeast
• Language: croatian
• URN:NBN: urn:nbn:hr:159:593622
• Study programme: Title: Molecular Biotechnology; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka molekularne biotehnologije (magistar/magistra inženjer/inženjerka molekularne biotehnologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2021-03-17 12:11:43