Določanje pristnosti hmelja (Humulus lupulus L.) in analiza aromatičnih sestavin hmelja v pivu

doktorska disertacija

Miha Ocvirk (Author), Iztok Jože Košir (Mentor), Nives Ogrinc (Thesis defence commission member), Nataša Poklar Ulrih (Co-mentor)

Abstract

Keywords

hmelj;Humulus lupulus L.;hmeljni ekstrakt;alfa-kisline;izo-alfa-kisline;eterično olje;pivo;hmeljenje;višji alkoholi;estri;aroma;diferencialna dinamična kalorimetrija;HS-SPME;GC;MS;GC-FID;FTIR;HPLC;avtentičnost;geografsko poreklo;botanična pristnost;izotopska razmerja ogljika;izotopska razmerja dušika;izotopska razmerja žvepla;GC-C-IRMS;kemometrija;

Data

Language:	Slovenian
Year of publishing:	2018
Typology:	2.08 - Doctoral Dissertation
Organization:	UL BF - Biotechnical Faculty
Publisher:	[M. Ocvirk]
UDC:	633.791:663.4:543.2/.9
COBISS:	4917112
Views:	3
Downloads:	0
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Determination of hop (Humulus lupulus L.) authenticity and analysis of hop aroma compounds in beer
Secondary abstract:	The aim of this study was to determine the botanical origin of hops (Humulus lupulus L.), from the results of analysis of the amount and contents of essential oil and contents of alpha- and beta-acids, which are genetically influenced. With the use of multivariant statistics, we have successfully distinguish between the five most common cultivars grown in Slovenia. For the determination of geographical origin, we have collected 77 samples of hop cones which are representative of the major hop-growing regions of the World. Isotopic ratios can act as fingerprints for different growing regions from around the world and we observe clustering of hop samples based on significant differences between growing regions based on δ15N and δ34S values. The δ13C values which are the least discriminative in determination of geographical origin, proved to be the most discriminative in determination of botanical origin of four Slovenian varieties. We made a clustering of beer samples on appropriate ones and ones with some minor deviations, based on the results of analysis of aroma profile and contents of higher alcohols and esters in combination with chemometrics. Our results show that these deviations in beer aroma are not a consequence of a permanent repeatable error in the brewing process, because the samples with deviations are not forming their own unique group, but are scattered around appropriate ones. The optimal time of hopping with intent to achieve high bitterness is no longer, than 100 min. Cooking longer leads to degradations of iso-alpha-acids. During wort boiling, great reductions of hop essential oil components are noticed, even to the bellow detection limit. We have shown that, even though hop extracts consist of around 70 % of alpha- and beta-acids, isomerization process of alpha-acids are not responsible for the observed thermal transitions.
Secondary keywords:	hop;Humulus lupulus L.;hop extract;alpha-acids;iso-alpha-acids;essential oil;beer;hopping;aroma;higher alcohols;esters;differential scanning calorimetry;HS-SPME;GC;MS;GC-FID;FTIR;HPLC;authenticity;geographical origin;botanical origin;stable isotope carbon ratio;stable isotope sulphur ratio;stable isotope nitrogen ratio;GC-C-IRMS;chemometrics;
Type (COBISS):	Doctoral dissertation
Study programme:	0
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Biotehniška fak.
Pages:	VIII, 88 f.
ID:	10937957