Exploring the composition and potential uses of four hops varieties through different extraction techniques.

Hydrophilic, lipophilic extracts and essential oil of four hops varieties from Slovenia were examined in this study. Lipophilic extracts were obtained by supercritical extraction (SFE), while for hydrophilic extracts ultrasound and microwave extraction were employed. Essential oils were isolated by the hydrodistillation process. The lipophilic composition of essential oils and lipophilic extracts was determined by GC-MS analysis. Monoterpenes and sesquiterpene hydrocarbons were the most abundant class of compounds in oils (62.27-79.65 %), with myrcene being the most abundant constituent. Limonene and trans-caryophyllene were two terpenes determined in all essential oils while only trans-caryophyllene was detected in SFE samples. Antioxidant, antimicrobial, and cytotoxic activity, determined by applying in vitro assays, was more influenced by extraction technique than by varieties. Molecular docking was carried out to gain insight into the potential cancer protein targets BCL-2 and MMP9, whereby humulene epoxide II displayed good binding configuration within the cavities of the two proteins.

Corrigendum to: Impact of Successive Exploitation of a Saccharomyces pastorianus Starter Culture on Saccharide Uptake Dynamics from Wort (Published: Food Technol. Biotechnol. 59 (1) 16-23 (2021) https://doi.org/10.17113/ftb.59.01.21.6899).

[This corrects the article DOI: 10.17113/ftb.59.01.21.6899.].

Extraction of Polyphenols from Slovenian Hop (Humulus lupulus L.) Aurora Variety Using Deep Eutectic Solvents: Choice of the Extraction Method vs. Structure of the Solvent.

Polyphenols from Slovenian hops (Humulus lupulus L.) of the Aurora variety were extracted by different methods and using classical solvents and several deep eutectic solvents (DES) based on choline chloride as the hydrogen bond acceptor component. The obtained extract solutions were analyzed by HPLC for the content of extracted α- and ß-acids and extracted xanthohumol. It was found that choline chloride:phenol DES concentrated aqueous solution had an extraction efficiency close to that of diethyl ether, which is considered one of the best classical extraction solvents for polyphenols from hops. The comparison of the extraction efficiency with other choline chloride-based DESs showed that the chemical similarity of the phenol ring in the solvent DES with the polyphenols in hops may be crucial for a highly efficient extraction with choline chloride:phenol DES. On the other hand, the choice of extraction method and the viscosity of the solvents tested seem to play only a minor role in this respect. As far as we know, this is the first study to attempt to relate extraction efficiency in the extraction of hydrophobic solutes to the compressibility of the DES extractants, the latter of which may be correlated with the extent of hydrophobic hydration around the DES components. In addition, using the heating and stirring method for the preparation of choline chloride-based DES concentrated aqueous solutions we found no support for the occurrence of water in two different roles (in the structural and in the dilution role) in these solvents.

The Stability of Hop (Humulus lupulus L.) Resins during Long-Period Storage.

The stability of alpha-acids, beta-acids and hop storage index (HSI) values under different conditions (aerobic/anaerobic, 4 °C/room temperature) was studied in a two-year trial. Six different varieties (Celeia, Aurora, Bobek, Styrian Gold, Savinjski Golding and Styrian Wolf) were used in the form of cones and pellets. Alpha- and beta-acids were determined by HPLC and HSI by spectrophotometry. Anaerobic conditions at 4 °C were best for alpha-acids, beta-acids and HSI values; however, 10-35% of the alpha-acids were still lost after two years. The decline was greater (63-99%) under aerobic conditions and at room temperature. Alpha-/beta-acid ratios increased in hop cones and decreased in hop pellets, whereas HSI values increased in all storage conditions. Overall, the performance was better for pellets than for hop cones. Storage conditions, storage form and hop variety had significant effects on the stability of hop resins.

The Impact of Hop Freshness on Kettle-Hopped Beers.

Hops are an indispensable ingredient in beer, and the differences in their chemical composition impart the various tastes and aromas associated with different beers. However, during storage, hops undergo changes in their chemical composition. Here, the changes in aroma and bitterness of kettle-hopped beers were evaluated in an experiment conducted on three different hop varieties (Aurora, Celeia and Styrian Wolf) with five different hop storage index (HSI) values (0.3-0.7). Hops were added to boiling wort for 5, 45 and 90 min. Alpha-acids, iso-alpha-acids, humulinones, bitterness units and hop aroma compounds in the samples were chemically analysed. All samples also underwent sensorial analysis. The old hops were not problematic in terms of bitterness or early hopping time. However, later additions of old hops reduced the quality and intensity of the hop aroma. The limit value for use without negative consequences for kettle hopping was set at HSI 0.5 for Aurora and Celeia and HSI 0.6 for Styrian Wolf.

Changes in Hop (Humulus lupulus L.) Oil Content and Composition during Long-Term Storage under Different Conditions.

Hop essential oil, in addition to alpha-acids, is one of the most valuable parameters for brewers, since it is responsible for beer aroma. The hop oil content and hop oil chemical composition deliver various aromas to beer. During storage, the hop chemical composition undergoes many physical and chemical changes that impact its quality. The main purpose of our study was to evaluate the changes occurring in hop oil content and its chemical composition during two years of storage under four different conditions (anaerobic, aerobic, cold room (4 °C), and room temperature) in the form of cones and pellets, supplied by local suppliers in Slovenia. Hop oil content and composition were determined by steam distillation and GC-FID. The greatest decrease in hop essential oil content occurred when the hops were stored under aerobic conditions and at room temperature. Monitoring of eight hop oil compounds under various conditions revealed different behaviors of the changes. The best storage conditions were anaerobic at low temperatures. Oxygen resistance was lower for pellets than for hop cones, whereas high temperature was more devastating for hop cones. In addition to the storage conditions, the hop variety and form were important factors regulating the extent of changes in hop oil content and chemical composition.

Impact of Hop Freshness on Dry Hopped Beer Quality.

The hop plant is seasonal, but beer production continues throughout the whole year. The quality of hops begins to decrease immediately after harvesting; therefore, maintaining the highest possible quality is important. A good indicator of hop freshness is the hop storage index (HSI). In this study, three different varieties of hops with five different HSI values, from 0.3 to 0.7, were used for brewing with the dry hopping technique. The main goal was to evaluate the impact of the HSI value on beer quality in terms of hop aroma and bitterness. Alpha acids, iso-alpha acids, humulinones, bitterness units and hop aroma compounds were chemically analysed. Sensorial analysis was also conducted on all samples. Decreases in the intensity and quality of hop aroma were detected with increasing HSI. The quality of bitterness was also reduced. High HSI also led to undesirable gushing. Beers brewed with hops with HSI values greater than 0.4 had deviations in aroma and bitterness when compared with beers brewed with fresh hops.

Antimicrobial Properties of Different Hop (Humulus lupulus) Genotypes.

The antimicrobial activity of hop extracts obtained from different hop genotypes were investigated against Staphylococcus aureus and Lactobacillus acidophilus. In this study the pure xanthohumol, purified ß-acids rich fraction, as well as α-acids with ß-acids rich fraction were used to test antimicrobial activity against Staphylococcus aureus and Lactobacillus acidophilus; whereby, the antimicrobial activity of different hop extracts against Lactobacillus acidophilus was studied for the first time. Microbial susceptibility to purified hydroacetonic extracts from different hop varieties was investigated by the broth microdilution assay to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). The hop hydroacetonic extracts were more effective against Staphylococcus aureus than against Lactobacillus acidophilus. Strong inverse correlations of MIC and MBC values were obtained with xanthohumol, cohumulone, n+adhumulone, colupulone and n+adlupulone contents, suggesting that the identified chemical hop compounds are directly responsible for antimicrobial effects. Moreover, the effect of the growth medium strength on the MIC values of hop extracts against Staphylococcus aureus was systematically investigated for the first time. The current study also reveals the effect of different hop extracts on Staphylococcus aureus, which responds to their presence by lag phase extension and generation time prolongation.

Differences in the Levels of the Selected Phytoestrogens and Stable Isotopes in Organic vs. Conventional Hops and Beer.

Xanthohumol (XN), isoxanthohumol (IX) and 8-prenylnaringenin (8-PN) are important prenylflavonoids present in hops with potential beneficial properties. In this study, we examined differences in the content of XN, IX and 8-PN in hops and beer produced under organic and conventional production regimes. A An ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) method for analysing XN, IX and 8-PN in hops and beer was developed and validated, with LOQ ranging from 0.5 to 10 ng/mL. Finally, we examined 15N/14N and 12C/13C isotope ratios in the hops and beer using isotope ratio mass spectrometry (IRMS). The results show no statistically significant difference in the content of the selected prenylflavonoids between organic and conventionally produced hops and beer-in the whole sample group, as well as between the matched pairs. Stable isotope analysis indicated that only δ15N values are statistically higher in organically produced hops and beer. However, the differentiation according to the type of production could not be made solely based on the δ15N signature, but it could be used to provide supporting evidence.

Sub- and Supercritical Extraction of Slovenian Hops (Humulus lupulus L.) Aurora Variety Using Different Solvents.

This work investigates the efficiency of supercritical fluid extraction of hops with a variety of solvents including carbon dioxide (CO2), propane, sulfur hexafluoride (SF6), and dimethyl ether (DME) at various densities (low-density and high-density). Operating parameters were 50 bar, 100 bar and 150 bar and 20 °C, 40 °C, 60 °C and 80 °C for all solvents, respectively. The influence of process parameters on the total yield of extraction and content of bitter acids in the extracts has been investigated. The mathematical model based on Fick's second law well described the experimental extraction results. Furthermore, HPLC analysis has been used to determine α- and ß-acids in extracts. The yield of bitter compounds in hop extracts was largely influenced by the type of solvent, the temperature and pressure applied during extraction. The results show that CO2 and propane were roughly equivalent to DME in solvating power, while SF6 was a poor solvent at the same conditions. The highest yield as well as the highest concentration of bitter acids in extracts were obtained by using DME, where the optimal operating conditions were 40 °C and 100 bar for the extraction of α-acids (max. concentration 9.6%), 60 °C and 50 bar for the extraction of ß-acids (4.5%) and 60 °C and 150 bar for the maximum extraction yield (25.6%).

Impact of Successive Exploitation of a Saccharomyces pastorianus Starter Culture on Saccharide Uptake Dynamics from Wort.

RESEARCH BACKGROUND: The production of lager beer includes successive repitchings of a single Saccharomyces pastorianus starter culture. During the beer production process, the yeast is exposed to several stress factors which could affect the fermentation performance. An incomplete fermentation represents a waste of fermentable extract and leads to a beer with higher carbohydrate levels, which could result in a beer with an atypical flavour profile. The aim of the present study is to determine the impact of successive exploitation of a single S. pastorianus starter culture on the wort saccharide uptake dynamics. EXPERIMENTAL APPROACH: The fermentation was monitored during the production of twelve batches of beer, where the starter yeast culture was reused twelve times without any further treatment. The following beer production steps were monitored: wort production, yeast starter culture propagation, primary fermentation, secondary fermentation and the final product. The work was conducted on an industrial scale employing standard process conditions. RESULTS AND CONCLUSIONS: Monitoring of the starter culture viability during successive fermentations indicated no reduction in the viability and vitality of the yeast culture. Monitoring of the fermentable wort saccharide concentrations (glucose, fructose, disaccharides and trisaccharides) revealed a correlation between an improvement in saccharide utilisation and starter culture age. Saccharide uptake efficacy proportionally matched the repitching frequency. Successive exploitation of S. pastorianus starter culture has a positive impact on the dynamics of saccharide utilisation from classical hopped wort and the young beer. Furthermore, the final lager beer contains no residues of fermentable saccharides that could affect the overall quality and flavour profile. NOVELTY AND SCIENTIFIC CONTRIBUTION: Results showed the impact of twelve successive wort fermentations on the dynamics of saccharides uptake that gives brewers important information. The added value of the experiment is all the work done on the industrial scale, with control of all processes and usage of exactly the same raw materials. This study contains usable technological data on the behaviour of saccharides during brewing on the industrial scale, which is not yet found in the literature.

Hop Compounds: Extraction Techniques, Chemical Analyses, Antioxidative, Antimicrobial, and Anticarcinogenic Effects.

Hop plants comprise a variety of natural compounds greatly differing in their structure and properties. A wide range of methods have been developed for their isolation and chemical analysis, as well as for determining their antioxidative, antimicrobial, and antigenotoxic potentials. This contribution provides an overview of extraction and fractionation techniques of the most important hop compounds known for their health-promoting features. Although hops remain the principal ingredient for providing the taste, stability, and antimicrobial protection of beer, they have found applications in the pharmaceutical and other food industries as well. This review focuses on numerous health-promoting effects of hops raging from antioxidative, sedative, and anti-inflammatory potentials, over anticarcinogenic features to estrogenic activity. Therefore, hops should be exploited for the prevention and even healing of several prevalent diseases like cardiovascular disorders and various cancer types. New ideas for future studies on hops are finally presented: computational investigations of chemical reactivities of hop compounds, nanoencapsulation, and synergistic effects leading to a higher bioavailability of biologically active substances as well as the application of waste hop biomass from breweries for the production of high-added-value products in accordance with the biorefinery concept.

The determination of the geographic origins of hops (Humulus lupulus L.) by multi-elemental fingerprinting.

For brewers, it is important to know the geographic origins of the hop plants (Humulus lupulus L.) used in their brewing processes since the contents and compositions of the bitter resins and essential oils in them depend on the environmental conditions during their growth. In this study, the multi-elemental profiles of hop plants from each of the world's main growing regions were determined by non-destructive energy dispersive X-ray fluorescence spectrometry (EDXRF). Understanding the multi-element profiles of the plants could be a useful tool in determining the geographic origins of produced hop plants.

Determination of the Geographical and Botanical Origin of Hops (Humulus lupulus L.) Using Stable Isotopes of C, N, and S.

A need exists for a reliable method to determine the geographical and botanical origin of hops. For this study, three sets of samples were collected: the first set comprised 5 German samples; the second set comprised samples of hops from 10 of the world's major hop-growing regions; and the third comprised the 4 main Slovenian regions. The samples were analyzed using isotope ratio mass spectrometry (IRMS) to obtain δ13C, δ15N, and δ34S values. The δ15N (2.2 ‰ to 8.4 ‰) and δ34S (0.7 ‰ to 12.3 ‰) values were the most discriminating parameters for classifying hop according to geographical origin. ANOVA showed distinct groupings for 8 out of the 10 hop-growing regions. Although it was not possible to distinguish the geographical origin of hops based on δ13C (-28.9 ‰ to -24.7 ‰), in the case of botanical origin, δ13C values proved to be the most discriminative albeit with limited success.

Antioxidant and Antimicrobial Properties of Veronica spicata L. (Plantaginaceae).

Tea made from Veronica spicata L. (syn. Pseudolysimachion spicatum (L.) Opiz, family Plantaginaceae) herb is used in traditional medicine as expectorant for cough and throat rinsing. To get insight into chemical compounds of V. spicata, the essential oil content (analysed by GC-FID and GC-MS), the content of phenolic compounds (analysed by HPLC), the content of macroelements and trace elements (analysed by ICP-AES), quantity of total phenols and total flavonoids (analysed by UV/Vis spectrophotometer), and antioxidant and antimicrobial properties were investigated. The main compounds of the essential oil were phytol (21.13%), heptacosane (10.22%) and pentacosane (8.91%). The most abundant investigated macroelement was K (8261 mg/kg) while Fe was the most represented element (32.49 mg/kg) among investigated micronutrients. Ten phenolic compounds (chrysin, rutin, quercitrin, quercitrin, and cichoric, ferulic, protocatehuic, rosmarinic, syringic and tannic acid) were identified and quantified. Additionally, V. spicata extract demonstrated notable radical-scavenging and chelating properties. The bacterial and fungal strains used in study were found to be susceptible toward methanolic and ethyl-acetate extracts with MIC values between 1.25 and 5.00 mg/mL using microdilution method. Aquose extracts were found to be antimicrobial inactive.

Antimicrobial and Antioxidant Properties of Satureja Montana L. and S. Subspicata Vis. (Lamiaceae).

Satureja montanaL. and S. subspicata Vis. (Lamiaceae) are used for centuries in traditional medicine of Balcanic people in the healing of the lymphatic nodule and respiratory system inflammation. In this paper the amount of total phenols and flavonoids (analyzed by UV/Vis spectrophotometry), phenolic compounds profile (analyzed by HPLC), antimicrobial and antioxidant activities were studied in samples collected in seven per species populations of S. montanaand S. subspicatain Croatia. Eight phenolic compounds (rutin, quercetin, caffeic, p-coumaric, ellagic, protocatehuic, rosmarinic, and syringic acid) were identified and quantified using HPLC in methanolic and ethanolic extracts. Results showed that both species contained polyphenolics and other antioxidant compounds with chelating and radical-scavenging properties. The extracts prepared from both species showed broad spectrum of antimicrobial activity on in vitrotested microbial species (Staphylococcus aureus, Escherichia coli, Candida albicans, C. dubliniensis, C. krusei, C. glabrata, C. parapsilosis, and Microsporum gypseum).

The influence of serial repitching of Saccharomyces pastorianus on its karyotype and protein profile during the fermentation of gluten-free buckwheat and quinoa wort.

Gluten-free beer-like beverages from malted buckwheat and quinoa are somehow close to their commercial production, but rather high expenses are expected due to the relatively high price of grain, some technological adaptations of process and the need for external enzyme supplementation during mashing. One of the common and efficient cost reduction measures in the industrial scale is serial repitching of the yeast biomass, which has not been studied for the buckwheat and quinoa wort fermentation before. In that manner we have monitored possible changes in yeast's proteins and chromosomal DNA during eleven serial repitchings of the yeast Saccharomyces pastorianus strain TUM 34/70 for fermentation of the barley, buckwheat and quinoa wort. Karyotypes showed changes in regard to the raw materials used and many responsible candidate proteins are suggested which could cause these differences. Different relative expressions of some protein bands were also linked to the proteins involved in yeast stress response and proteins involved in fermentation performance. Results suggest that serial repitching of the strain TUM 34/70 seems suitable for the production of gluten-free beer-like beverages from buckwheat and quinoa.

Influence of two hop (Humulus lupulus L.) varieties on in vitro dry matter and crude protein degradability and digestibility in ruminants.

BACKGROUND: Hop cones contain several antimicrobial substances. The aim of the study was to determine the effects of two hop varieties, Aurora and Dana, on substrate (diet for a dairy cow, producing 30 kg milk daily) in vitro dry matter (DM) and crude protein (CP) degradability and digestibility. RESULTS: In the in vitro trial freshly ground hops were added to the buffered rumen fluid in concentrations simulating the cow's daily intake of 50, 100 and 200 g of hops. Increasing the concentration of hops decreased (P < 0.05) both the average in vitro DM degradabilities of substrate from 725 to 592, 553 and 481 g kg(-1), respectively, and in vitro CP degradabilities of substrate from 752 to 566, 561 and 478 g kg(-1), respectively. The reduction of in vitro DM and CP degradability is counterbalanced by the (invariable) in vitro DM and CP digestibility. The difference between CP digestibility and degradability represents an estimate of the amount of rumen 'bypass' protein which increased with increasing concentration of hops from 172 to 454 g kg(-1). CONCLUSIONS: Decreased DM and CP degradability and increased amount of rumen 'bypass' protein could lower the amounts of protein required by high-producing ruminant animals. However, this supposition needs a validation with in vivo trials.

Effect of deodorization of camelina (Camelina sativa) oil on its phenolic content and the radical scavenging effectiveness of its extracts.

The influence of deodorization parameters (temperature (T), steam flow (S), time (t)) on the phenolic content and radical scavenging effectiveness (RSE) of methanolic extracts of camelina oil was investigated and analyzed by response-surface methodology (RSM). The phenolic content can be considered to be a linear function of all three parameters. A positive linear relationship between the content of phenolic compounds in deodorized oils and RSE was observed. Deodorization at 210 °C with a steam flow of 3 mL/h for 90 min resulted in the best preservation of phenolics, amounting to 29.9 mg/kg. The lowest reduction from RSE of 12.4 µM Trolox equivalents (TE)/g oil for the crude oil was observed for oil treated at 195 °C and 18 mL/h for 60 min with RSE of 10.1 µM TE/g oil. The lack of correlation between RSE or total phenolic content and oxidative stability (OS) of the deodorized oils suggests that antioxidants in scavenging radicals react by different mechanisms, depending on radical type and reaction medium.

Investigation of chemical compounds, antioxidant and antimicrobial properties of teucrium arduini L. (lamiaceae).

In this paper chemical composition of the essential oil (analysed by GC and GC-MS), the content of phenolic compounds (analysed by HPLC), quantity of total phenols and total flavonoids (analysed by UV/Vis spectrophotometer), antioxidant and antimicrobial activities of ethanolic extracts were investigated in endemic Teucrium arduini L. in population of Mt Biokovo (Croatia). The oil was characterized by a high concentration of sesquiterpene hydrocarbons (70.4%) of which ß-caryophyllene (35.2%) and germacrene D (18.7%) being the major compounds. Three phenolic compounds (quercetin, ferulic acid and rosmarinic acid) were identified and quantified in ethanolic extract of T. arduini using HPLC. The results also showed that T. arduini is a source of polyphenolic and other antioxidants with radical-scavenging and chelating properties. The ethanol extracts prepared from the leaf of T. arduini showed broad spectrum of antimicrobial activity on Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Candida albicans and Aspergillus brasiliensis, which are susceptible on concentration below or equal to 4.00 mg/mL, whilst Microsporum gypseum was resistant at investigated concentrations.