When hops are added to beer, varying degrees of hoppy aroma persist in the finished beer as a result of a number of factors. Dry-hopping is a technique whereby hops are added to beer post-fermentation to leverage the maximum aroma potential of the hop essential oils while minimizing bitterness contribution...
Hop aroma in beer is related to the unique compositional chemistry of the hops used in the brewing process. While the range of these compositions is quite diverse and primarily dependent on hop cultivar¹, other studies have also shown that cultivation, seasonality, harvesting², processing³⁴, and storage practices⁵⁶ contribute to differences...
This work set out to examine whether ethanol content can influence the human detection of volatile hop compounds in beer. Advances in chromatography have identified hundreds of chemical compounds in the essential oil of hops but only a fraction are directly associated with "hoppy" aroma. To screen compounds, sensory detection...
This work set out to examine the potential contribution of five aliphatic lactones, γ-nonalactone, γ-decalactone, γ-dodecalactone, δ-decalactone and δ-dodecalactone to stone fruit aroma in beer. This work consists of three related studies; lactone olfaction thresholds, additive/synergistic aroma effects and a gas-chromatography-mass-spectrophometry method of analysis. First was the determination of these...
The goal of this research was to investigate the bitterness intensity of known hop acid oxidation products, humulinones and hulupones. This was carried out by first creating suitable extracts of humulinones and hulupones of high purity for sensory testing. Using previously established oxidation methods and the addition of preparative liquid...
This research sought to determine the origin of bitterness as a result of dry-hopping. An unhopped ale was dry-hopped and examined in the controlled dry-hop experiment and commercial beers were examined for chemical changes from dry-hopping in the commercially dry-hopped beer survey. This thesis work suggested specific bitter hop components...
The objectives of this study were to 1) measure and compare the compositional differences of essential oil among three hop cultivars ('Centennial’, 'Citra' and 'Nelson Sauvin'), 2) identify the odor-active aroma compounds in three varieties of hops and 3) investigate the behavior of hop-derived aroma compounds in beers prepared by...
The stability of diacetyl in fermented milk and the removal of
diacetyl from beer were studied. A convenient method for the determination
of diacetyl in beer, established by Owades and Jakovac, was
modified and applied for flavor analyses of dairy products. Through
this method, diacetyl in 12 samples could be...
Hops (Humulus lupulus L.) are primarily used to provide specific characteristics to beer, such as bitterness, aroma, flavor, and microbial stability. The chemical composition of hops, relative to how they are used during the brewing process, dictates the expression of these characteristics. Of the raw ingredients that go into making...
This work set out to examine the methodologies of dry hopping, compare different hop materials, and look at the extraction behavior of different types of hop compounds. This work consists of two discrete studies, where the first study informed the design of the second.
The first study measured the concentrations...
This study examined whether polyphenols contribute a harsh bitterness
to beer, and how polyphenols may otherwise modify beer bitterness in the
presence of iso-a-acids. The experimental portions of this project were
divided into effectively two segments. The first section of the study
encompassed groundwork polyphenol extraction development, and the
examination...
Malt, wort and beer samples representing a single
pilot brew were extracted from Celite columns with Freon
114. Total extracts were analyzed by gas
chromatography/mass spectrometry. Compounds were
identified that were unique or common to beer, wort or
malt and quantities present were determined for those
common to the three...
Staling in beer is inevitable. Oxidation and increased temperatures are the main causes of stale flavors in bottled beers. Since 1934, research has been done to identify compounds and pathways involved in creating stale flavors. Although many research papers report stale flavors, there is not a lexicon per se of...
Beer is one of the most extensively consumed beverages world-wide and it is almost always brewed with hops (Humulus lupulus, L.). Hops provide beer with bitterness, aroma, flavor and texture and also enhance specific beer properties such as foam stability, clarity (colloidal stability), color, flavor stability and microbial stability. Hops...
Alpha acids are found in the lupulin glands of hops cones. These acids have no bitterness of their own, but can be isomerized and subsequently hydrogenated to form bitter iso-α-acids and tetrahydroiso-α-acids respectively. Current literature values for the detection thresholds of iso-α-acid and tetrahydroiso-α-acid in lager beer have been reported...
Hop derived bitter compounds, including alpha-acids, reduced and non-reduced iso-alpha-acids, were evaluated for their contribution to peak bitter intensity in lager beer. Alpha-acids are the precursors to the major bittering components in beer (iso-alpha-acids). Typically, alpha-acids do not survive the brewing process, but if a product is dry-hopped, they may...