Qualitative determination of β-acids and their transformation products in beer and hop using HR/AM-LC-MS/MS

A Preliminary Study on the Effect of Adding Sugarcane Syrup on the Flavor of Barley Lager Fermentation

This study focuses on the diversified utilization of the sugarcane industry, and sugarcane syrup, as a by-product of the sugarcane industry, is a good raw material for fermentation. Bringing sugarcane syrup into beer is conducive to the enrichment of the sugar industry, and it can improve the flavor of beer and make it more aromatic. This study determined the optimal fermentation process for beer. By analyzing the consumption rate of the carbon and nitrogen sources of raw materials, the nutrient utilization of yeast, and the causes of differences in flavor substances, the flavor composition and flavor stability of beer were determined by SPME-HS-GC-MS technology. The results showed that beer brewed with sugarcane syrup as an auxiliary raw material met the basic specifications of beer. The addition of sugarcane syrup to the wort base increased the utilization of amino acids by the yeast, and LS (lager with added cane syrup) increased the nine flavor compounds of the beer, which constituted the basic flavor of the beer, bringing new flavor compounds compared with the normal all-barley beer. Forced aging experiments showed that LS produced fewer aging compounds than OWBL. Various experiments have shown that it is feasible to ferment beer with sugarcane syrup instead of partial wort.

Quantification of Hop-Derived Bitter Compounds in Beer Using Liquid Chromatography Mass Spectrometry

Hops (Humulus lupulus L.) are essential raw materials for beer brewing, and the major contributors to beer bitterness are isohumulones (iso-α-acids) and humulinones. In recent years, many breweries have focused on the production of hop-forward beer styles by adding hops after or during the cold fermentation stage, which will tend to release humulinones or other hop-derived bitter compounds. In this study, a LC-MS/MS method was developed for quantification of 60 hop-derived bitter compounds in 25 min. Reverse-phase chromatography with an alkaline methanol/acetonitrile (70:30) mobile phase was used for the separation. The quantitative range was 0.053-3912 ng/mL with correlation coefficient r > 0.99, and the LOQ were 0.26 and 0.053 ng/mL for iso-α-acids and humulinones. Precision (RSD < 5.0%) and accuracy (recovery 86.3%-118.1%) were both satisfactory. The abundance of hop-derived bitter compounds in the dry-hopped beer (Double-India Pale Ale) and the nondry-hopped beer (Vienna Lager) were monitored throughout the fermentation and storage stages, and the formation of oxidation and cyclization products showed difference profiles between these two beers. The quantification results reveal how hop-derived bitter compounds change throughout the brewing process, as well as the influence of hops and brewing techniques on beer bitterness.

Sensomic comparison of lager beers fermented by selected Saccharomyces pastorianus yeast strains

Selection of the appropriate yeast strain is one of the most crucial steps in a brewery. Traditionally, yeast strain's abilities during beer fermentation are described according to brewer's experiences. Hence, these descriptions could be inaccurate and strictly based on sensory experiences. In this study, lager beers fermented by four traditional bottom-fermented yeast strains were characterized in detail by sensomic approach. The obtained results revealed that yeast strains can influence most of the sensory-related components in beer, not only esters and higher alcohols, but also carbonyls, amino acids, saccharides, fatty acids, heterocyclic compounds, hop oils, and other hop-related components. By comparison of chemical and sensory characteristics of each studied beer, the theoretical importance of sensory interactions on beer flavor perception was also revealed as the general conception that the beers with similar flavors have also similar chemical profiles (and vice versa) was seemed as not valid.

Biopreservation of beer: Potential and constraints

The biopreservation of beer, using only antimicrobial agents of natural origin to ensure microbiological stability, is of great scientific and commercial interest. This review article highlights progress in the biological preservation of beer. It describes the antimicrobial properties of beer components and microbiological spoilage risks. It discusses novel biological methods for enhancing beer stability, using natural antimicrobials from microorganisms, plants, and animals to preserve beer, including legal restrictions. The future of beer preservation will involve the skilled knowledge-based exploitation of naturally occurring components in beer, supplementation with generally regarded as safe antimicrobial additives, and mild physical treatments.

Radical Intermediates in the Degradation of Hop Acids

Radical formation in isohumulones was investigated under different types of stress, including temperature, transition metal ions, and hydrogen peroxide. Including dihydroisohumulones and tetrahydroisohumulones, as relevant analogues, allowed us to evaluate critical functionalities in radical formation. Using spin-trapping methodology with 5,5-dimethyl-1-pyrroline N-oxide and N-tert-butyl-α-phenylnitrone as relevant traps, followed by simulation of corresponding spin adducts, identification of incipient radicals was attempted. The isohexenoyl side chain in isohumulones, but not present in dihydro- and tetrahydroisohumulones, was most sensitive to radical formation. Kinetic profiles further demonstrated that radical formation in this moiety was accelerated in the presence of ferrous ions. Reactivity of parent six-membered-ring humulones in radical formation was different, as scavenging of free radical species was more important. Lupulones, despite similarity with humulones, showed a different behavior with an obvious radical decay pathway during ageing, mainly ascribed to radical formation on the ring structure. Quantification of final spin adducts allowed us to determine absolute importance of the different degradation pathways. Eventually, mechanisms are presented explaining why isohumulones are more prone to radical processes in (aut)oxidation and thermal decay than close relatives such as dihydroisohumulones.

Ultra-Micro-Scale-Fractionation (UMSF) as a Powerful Tool for Bioactive Molecules Discovery

Herein is detailed the development and validation of an ultra-micro-scale-fractionation (UMSF) technique for the discovery of plant-based, bioactive molecules, coupling the advantages of ultra-performance liquid chromatography mass spectrometry (UPLC-MS) separations with microtiter plate-based bioassay screens. This novel one-step approach simultaneously uses UPLC to collect chemical profile information, while performing high-resolution fractionation, greatly improving workflow compared to methods relying on high-performance liquid chromatography (HPLC), solid phase extraction or flash systems for chromatographic separations. Using the UMSF technique, researchers are able to utilize smaller quantities of starting materials, reduce solvent consumption during fractionation, reduce laborious solvent dry down times, replace costly single-use solid-phase-extraction cartridges with reusable analytical-sale UPLC columns, reduce fractionation times to less than 10 min, while simultaneously generating chemical profile data of active fractions and enjoying superior chromatographic resolution. Using this technique, individual bioactive components can be readily purified, identified, and bioassayed in one step from crude extracts, thereby eliminating ambiguous synergistic effects often reported in plant-based natural products research. A successful case-study is presented illustrating the versatility of this technique in identifying lupulone as the principal cytotoxic component from hops (Humulus lupulus L.), using a brine shrimp (Artemia franciscana) model. These results confirm and expand upon previous cell-based bioassay studies using a more complex, multicellular organism, and add to our understanding of structure-function activity relationships for secondary metabolites in hops and the Cannabaceae plant family.

Quantification of co-, n-, and ad-lupulone in hop-based dietary supplements and phytopharmaceuticals and modulation of their contents by the extraction method

Hop β-bitter acids (lupulones) are health-beneficial components of Humulus lupulus L. showing, for example, antidepressant-like effects in vitro. Despite of the widespread use of hops for medicinal purposes, the concentrations of lupulones in hop-based drugs have not been reported yet. The present study developed, validated, and applied a method with external calibration, which allows for the first time separate quantification of co-, n-, and ad-lupulone in hop-based drugs by UHPLC‒DAD. Concentrations between 'not detectable' and 2.7 mg/mL co-lupulone, 2.2 mg/mL nlupulone, or 0.7 mg/mL ad-lupulone were measured in nine different commercial dietary supplements and phytopharmaceuticals. Only one hop tincture contained sufficient lupulone to possibly exert potential antidepressant effects. Aiming for products with increased lupulone content, the extraction efficiency of different solvents was investigated. Complete extraction of lupulones from raw hops was achieved by organic solvents including methanol and ethanol, whereas aqueous mixtures resulted in low recovery. These results indicate that adapted extraction conditions may result in more effective hops products.

Chemical Characterization of Beer Aging Products Derived from Hard Resin Components in Hops (Humulus lupulus L.)

The bitter taste of beer originates from resins in hops (Humulus lupulus L.), which are classified into two subtypes (soft and hard). Whereas the nature and reactivity of soft-resin-derived compounds, such as α-, β-, and iso-α-acids, are well studied, there is only a little information on the compounds in hard resin. For this work, hard resin was prepared from stored hops and investigated for its compositional changes in an experimental model of beer aging. The hard resin contained a series of α-acid oxides. Among them, 4'-hydroxyallohumulinones were unstable under beer storage conditions, and their transformation induced primary compositional changes of the hard resin during beer aging. The chemical structures of the products, including novel polycyclic compounds scorpiohumulinols A and B and dicyclohumulinols A and B, were determined by HRMS and NMR analyses. These compounds were proposed to be produced via proton-catalyzed cyclization reactions of 4'-hydroxyallohumulinones. Furthermore, they were more stable than their precursor 4'-hydroxyallohumulinones during prolonged storage periods.