Isomerized Hop Extracts Research Articles

Characterization and formation mechanisms of viable, but putatively non-culturable brewer's yeast induced by isomerized hop extract

In this study, the formation and resuscitation of a viable, but putatively non-culturable (VPNC) brewer's yeast under various concentrations of isomerized hop extracts were investigated. The isomerized hop extract (300 mg/L) treatment for 2 h completely induced yeast cells into the VPNC state. The VPNC cells incubated on YPD agars containing catalase (2500 U/plate) recovered their culturability within three days. Notably, the VPNC yeast had significantly lower fermentation efficiency during wort fermentation than the normal yeast, yielding lower ethanol contents. Beer produced by the VPNC yeast contained significantly fewer aromatic alcohols and esters. However, no significant differences were observed in the fermentation performance and the formation of flavor volatiles between the normal and resuscitated yeast. Our transcriptomic analysis further showed that the genes involved in the carbohydrate and amino acid metabolism, DNA replication, and cell division were downregulated in VPNC cells. Conversely, the TCA cycle, ABC transporter, organic acid metabolism, and oxidoreductase activities were increased. Moreover, we confirmed that Yap1 gene deletion suppressed the entry of yeast cells into the VPNC state. Overall, the increased survival ability, inhibited cell division, and reduced metabolic activity in the yeast might lead to the induction of an isomerized hop extract-induced VPNC state.

Dietary iso-α-acids prevent acetaldehyde-induced liver injury through Nrf2-mediated gene expression.

Acetaldehyde is the major toxic metabolite of alcohol (ethanol) and enhances fibrosis of the liver through hepatic stellate cells. Additionally, alcohol administration causes the accumulation of reactive oxygen species (ROS), which induce hepatocyte injury-mediated lipid peroxidation. Iso-α-acids, called isohumulones, are bitter acids in beer. The purpose of this study was to investigate the protective effects of iso-α-acids against alcoholic liver injury in hepatocytes in mice. C57BL/6N mice were fed diets containing isomerized hop extract, which mainly consists of iso-α-acids. After 7 days of feeding, acetaldehyde was administered by a single intraperitoneal injection. The acetaldehyde-induced increases in serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were suppressed by iso-α-acids intake. Hepatic gene expression analyses showed the upregulation of detoxifying enzyme genes, glutathione-S-transferase (GST) and aldehyde dehydrogenase (ALDH). In vitro, iso-α-acids upregulated the enzymatic activities of GST and ALDH and induced the nuclear translocation of nuclear factor-erythroid-2-related factor 2 (Nfe2l2; Nrf2), a master regulator of antioxidant and detoxifying systems. These results suggest that iso-α-acid intake prevents acetaldehyde-induced liver injury by reducing oxidative stress via Nrf2-mediated gene expression.

Gas Chromatography-Mass Spectrometry (GC-MS) Profiling of Hops and Some Nigerian Potential Hop Substitutes: Comparative Studies in Beer Brewing

Isomerized hop extract and methanolic extracts of Azadirachta indica, Garcinia kola, Gongronema latifolium and Vernonia amygdalina were profiled by the application of Gas Chromatography-Mass Spectrometry (GC-MS). The isomerized hop extract and ethanolic extracts of the plant species were used to brew beers. The aim was to study the GC-MS profiles of all the extracts comparatively and to investigate some physicochemical properties of beers brewed with hop extracts and in comparison, with beers brewed with extracts from the four Nigerian plants. The profiling of the metabolites in hop extracts and those of the Nigerian plants was carried out using Gas Chromatography - Mass Spectrometer. The physicochemical properties of the finished beer products were also carried out using standard methods. Beers brewed with extracts from the Nigerian plants were statistically ranked by the application of Analysis of Variance (ANOVA) to ascertain their potentiality. The GCMS results showed that these plants contained metabolites comparable to those of hops, although some metabolites [dehydro-cohumulunic acid; 4,4-dimethyl- 2-buten-4-olide; 1,2-dimethyl-cyclopropane carboxylic acid; lupulone; 2,5-dimethyl-2-hexanol; 4,4,5,5-tetramethylbicyclo hexyl-6-ene-2,3-dione; octadecanoic acid, oxiranyl methyl ester and 1,2-benzenedicarboxylic, bis(-2-ethyl hexyl) ester] present in hops were absent in the Nigerian plants. Isomerized hop, hop leaf, G. kola and V. amygdalina extracts contained 14, 11, 12 and 9 metabolites respectively while those of A. indca and G. latifolium contained 10 metabolites each. The physicochemical properties of the brewed beers revealed that the alcohol content in all the beer samples ranged from 3.43-3.75%, total acidity (0.132-0.324%), pH (5.47-5.68), turbidity (5-125NTU), total solids (3.66- 8.16%) and bitterness level (25.38-39.62IBU). The concentration of arsenic in the beer samples ranged from 1.44- 1.77ppm, cadmium (0.00-0.97ppm) and copper (0.10-2.70ppm). Test of significant (p-value) in all the tested plants was greater than 0.05 at 95% confidence interval. Consequently, the extracts from tested Nigerian plants could be used as suitable substitutes for hops in beer brewing without alteration of physicochemical properties of beer, G. kola having the greatest potential as substitute for hops.

Levels of Polycyclic Aromatic Hydrocarbons (PAHs) in Beers: Consumption and Public Health Concerns

Aim: The aim is to investigate some physicochemical properties of beers and polycyclic aromatic hydrocarbons contaminants in beer brewed with isomerized hop extract and in comparison with beers brewed with extracts from four Nigerian potential hop substitutes.
 Study Design: Beers were brewed using isomerized hop extract and extracts from four Nigerian bitter vegetables. Analyses of physicochemical properties of the beers and for the presence of 16 specific target PAHs were carried out using their respective standard methods.
 Place and Duration of Study: Analysis of physicochemical properties of the beers was done at Nigerian Breweries PLC, Enugu while analysis for PAHs was conducted at Central Laboratory, Nigerian Institute for Oceanography and Marine Research, Lagos between July, 2018 and November, 2019.
 Methodology: Physicochemical properties of the beers (alcohol content, bitterness level, pH, specific gravity, colour) were determined using their respective standard methods. Gas chromatography/mass spectrometry was used in analyzing for PAHs [naphthalene, acenaphthylene, acenaphthene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, indeno(1,2,3-cd)pyrene and benzo(g,h,i)perylene]. Four isotopically labelled PAHs (acenaphthene-d10, phenanthrene-d10, chrysene-d12 and perylene-d12) were used as internal standards.
 Results: Alcohol content (%v//v) in the beer samples is A(5.20); B(4.28); C(4.40); D(4.43) and E(4.54), bitterness level in International Bitterness Units (IBU) is A(0.54); B(0.80); C(1.46); D(1.46) and E(0.08), pH is A(4.36); B(3.08); C(3.88); D(3.90) and E(3.87), specific gravity is A(10.06); B(10.00); C(10.00); D(10.06) and E(10.06), and beer colour is A(5.80); B(7.70); C(6.60); D(8.00) and E(7.40). All 16 EPA PAHs were not found in all the beer samples except pyrene which was detected in sample B at a concentration of 0.00402 mg/kg.
 Conclusion: It is concluded that extracts from the four Nigerian bitter vegetables could be used as substitutes for isomerized hop extract and that consumption of beer produced using extract from G. kola poses great public health concerns.

Survival of probiotic strain Lactobacillus paracasei L26 during co-fermentation with S. cerevisiae for the development of a novel beer beverage

Amidst the rising popularity of craft beers, it would be opportune to develop a novel, unfiltered and unpasteurized sour beer with high probiotic live counts. However, as beer typically contains hop iso-α-acids that prevent the growth and survival of probiotic lactic acid bacteria, the use of suitable fermentation strategies is crucial. The growth, and survival of the probiotic bacterium, Lactobacillus paracasei L26, were assessed during a 10-day co-fermentation period with a brewer's yeast, Saccharomyces cerevisiae S-04, in unhopped wort. Isomerized hop extract was added prior to storage of the beers at 25 °C and 5 °C. During co-fermentation in unhopped wort, L. paracasei L26 maintained high viable cell counts above 8 Log CFU/mL, indicating species compatibility with the yeast. The majority of fermentable sugars were attenuated by S. cerevisiae S-04, with a concomitant production of alcohols and esters. Significant amounts of lactic acid were produced by L. paracasei L26 (P < 0.05). During storage with added isomerized hop extract, maximal probiotic viability enhancing effects were observed in the presence of live S. cerevisiae S-04, in combination with refrigeration. The results suggest that beers could be a vehicle for probiotic delivery under appropriate conditions. This was the first study demonstrating the feasibility of utilizing probiotic lactobacilli as starter cultures in beer brewing.

Acute improvement of endothelial functions after oral ingestion of isohumulones, bitter components of beer

Isohumulones, principal components of the bitter taste of beers, have antioxidant capacity. We studied i) the effects of oral ingestion of isomerized hop extract (IHE) on the endothelial functions in smokers as well as non-smokers and ii) the effects of IHE on cultured endothelial cells in high oxidative stress state. Twelve cigarette smokers and eleven non-smokers ingested IHE and placebo in a randomized crossover design. Flow-mediated vasodilatation (FMD) was measured using ultrasonography. We also studied the effects of isohumulones on i) the cell viability under hypoxia and ii) the levels of angiotensin II (AT-II)-induced reactive oxygen species (ROS) in the cultured human aortic endothelial cells (HAECs). At baseline, the FMDs of the smokers were significantly lower than those of the non-smokers. The FMDs increased significantly after 30 min and 120 min of IHE ingestion in both the smokers and the non-smokers. IHE protected the HAECs from hypoxia-induced cell death as assessed by cell viability. IHE also reduced the AT-II-induced intracellular ROS level. Oral ingestion of IHE appears to exert acute beneficial effects on the endothelial functions in both the smokers and non-smokers, and the in vitro experiments using HAECs suggested that the effect be through reducing intracellular oxidative stress.

EVALUATION OF ANTI-NUTRITIONAL FACTORS IN HOP EXTRACTS AND EXTRACT FROM AZADIRACHTA INDICA AS POTENTIAL SUBSTITUTE IN THE NIGERIAN BEER INDUSTRY

The anti-nutritional factors in Azadirachta indica (neem) as contrasted to hops were carried out in terms of their methanolic extracts. These factors (trypsin inhibitors, phytate, cardiac glycoside, oxalate, cyanogenic glycoside and hydrogen cyanide) were screened using standard methods. The result of the assay revealed that trypsin inhibitors ranged from 6.45-17.30%, phytate ranged from 0.99% to 1.68% while cardiac glycoside ranged from 3.5% to 6.0% and the concentration of oxalate ranged from 0.0405mg/100g to 0.1020mg/100g, cyanogenic glycoside ranged from 0.216ppm to 0.810ppm while hydrogen cyanide ranged from 0.540ppm to 1.404ppm. It was established from ranking that A. indica was closer to isomerized hop extract than to hop leaf extract in the content of anti-nutritional factors. Hence, the extract from A. indica could be used as suitable substitute for hops in beer brewing.

Molecular mechanisms behind the antimicrobial activity of hop iso-α-acids in Lactobacillus brevis

The main bittering component in beer, hop iso-α-acids, have been characterised as weak acids, which act as ionophores impairing microbial cells' function under acidic conditions as present in beer. Besides medium pH, divalent cations play a central role regarding the efficacy of the antimicrobial effect. The iso-α-acids' non-bitter derivatives humulinic acids can be found in isomerised hop extracts and can be generated during hop storage. Therefore, they have been under investigation concerning their influence on beer sensory properties. This study sketches the molecular mechanism behind iso-α-acids' antimicrobial activity in Lactobacillus (L.) brevis regarding their ionophore activity versus the dependence of the inhibitory potential on manganese binding, and suggests humulinic acids as novel tasteless food preservatives.We designed and synthesised chemically modified iso-α-acids to enhance the basic understanding of the molecular mechanism of antimicrobial iso-α-acids. It could be observed that a manganese-binding dependent transmembrane redox reaction (oxidative stress) plays a crucial role in inhibition. Privation of an acidic hydroxyl group neither erased ionophore activity, nor did it entirely abolish antimicrobial activity. Humulinic acids proved to be highly inhibitory, even outperforming iso-α-acids.

A powerful methodological approach combining headspace solid phase microextraction, mass spectrometry and multivariate analysis for profiling the volatile metabolomic pattern of beer starting raw materials

The volatile metabolomic patterns from different raw materials commonly used in beer production, namely barley, corn and hop-derived products – such as hop pellets, hop essential oil from Saaz variety and tetra-hydro isomerized hop extract (tetra hop), were established using a suitable analytical procedure based on dynamic headspace solid-phase microextraction (HS-SPME) followed by thermal desorption gas chromatography–quadrupole mass spectrometry detection (GC–qMS). Some SPME extraction parameters were optimized. The best results, in terms of maximum signal recorded and number of isolated metabolites, were obtained with a 50/30μm DVB/CAR/PDMS coating fiber at 40°C for 30min. A set of 152 volatile metabolites comprising ketones (27), sesquiterpenes (26), monoterpenes (19), aliphatic esters (19), higher alcohols (15), aldehydes (11), furan compounds (11), aliphatic fatty acids (9), aliphatic hydrocarbons (8), sulphur compounds (5) and nitrogen compounds (2) were positively identified. Each raw material showed a specific volatile metabolomic profile. Monoterpenes in hop essential oil and corn, sesquiterpenes in hop pellets, ketones in tetra hop and aldehydes and sulphur compounds in barley were the predominant chemical families in the targeted beer raw materials. β-Myrcene was the most dominant volatile metabolite in hop essential oil, hop pellets and corn samples while, in barley, the predominant volatile metabolites were dimethyl sulphide and 3-methylbutanal and, in tetra hop, 6-methyl-2-pentanone and 4-methyl-2-pentanone. Principal component analysis (PCA) showed natural sample grouping among beer raw materials.

Hop (Humulus lupulus L.) extract inhibits obesity in mice fed a high-fat diet over the long term

Hops (Humulus lupulus L.) are traditionally used to add bitterness and flavour to beer. Although the isomerised hop extracts produced by the brewing process have been thought to ameliorate lipid and glucose metabolism, the influence of untreated hop extracts on high-fat (HF) diet-induced obesity is unclear. The present study examined the anti-obesity effects of a hop extract in male C57BL/6J mice fed a HF diet, or HF diet plus 2 or 5% hop extract for 20 weeks. The oral glucose tolerance test was performed at week 19. Furthermore, water excretion was evaluated in water-loaded Balb/c male mice. The effects of the extract on lipid accumulation and PPARγ expression in 3T3-L1 adipocytes were examined. The hop extract inhibited the increase in body and adipose tissue weight, adipose cell diameter and liver lipids induced by the HF diet. Furthermore, it improved glucose intolerance. The extract enhanced water excretion in water-loaded mice. Various fractions of the hop extract inhibited lipid accumulation and PPARγ expression in 3T3-L1 adipocytes. Hop extracts might be useful for preventing obesity and glucose intolerance caused by a HF diet.

Thermal Deterioration of the Trans-/Cis-Ratio of Bittering Agents of Commercial Beers

The use of reduced isomerised hop extracts to achieve both bitterness and light stability became very popular during the last decade. Changes during storage in four hop extracts and seven commercial lager beers are studied using HPLC and spectrophotometric techniques. The degradation of the iso-α-acids and tetrahydro iso-α-acids as a function of time is represented by the ratio, in percentage, of the sum of trans-isomer concentration to the sum of the cis-isomer concentration (T/C). The results provided conclusive evidence that the gradual decreased of bitterness intensity in beer was due to the degradation of iso-α-acids, notably to the instability of the trans-iso-α-acids. When the beers were stored for 14 days at 45°C the decrease of the T/C average varied from 8.6 to 14.0%, except in lemon beer, in which case, T/C decreased 36.9%. The results allowed us to infer that in open storage and/or warm conditions the deterioration of beer was critical above 35°C. On the other hand, the results showed that tetrahydro iso-α-acids remained unaltered.

The Application of β-Cyclodextrin to Separate cis- from trans-Iso-α-Acids in an Isomerized Hop Extract

The cis-iso-α-acids that result from isomerization of hop α-acids, together with their trans-isomers, are the principal bitter components found in beer. Reports indicate cis-isomers are more stable than their trans-isomer counterparts. Therefore, the separation of cis-iso-α-acids could potentially contribute to the production of a more stable beer. Separation was performed using β-cyclodextrin. The optimum complexation conditions that yielded the purest cis-isomer mixture were achieved using water as a solvent at a complexation temperature of 70°C. The ratio of β-cyclodextrin mass to volume of water was 1:8, and the molar ratio of the total amount of iso-α-acids sample to β-cyclodextrin was 1:1. After 2 days of precipitation, the cis-isomer mixture that remained in the supernatant was subjected to ultrafiltration to remove the remaining β-cyclodextrin. The purest trans-iso-α-acids mixture was obtained using the same conditions, except that the molar ratio of the total amount of iso-α-acids sample to β-cyclodextrin was 4:1. The trans-isomers were released from the β-cyclodextrin complex by methanol elution. This method is promising for large-scale production of stereoisomers that can be applied in hopped beverages.

ANTI-OBESITY EFFECTS OF ISOHUMULONES BY MODULATING LIPOID METABOLISM VIA PEROXISOME PROLIFERATOR-ACTIVATED RECEPTORS

Obesity, the abnormal excessive growth of adipose tissue and accumulation of abdominal fat, results from the combined effects of excess energy intake and reduced energy expenditure. Obesity raises the risk for cardiovascular disease (CVD). Isohumulones, which impart bitter flavor and an antibacterial property to beers, are generated from humulones in the female inflorescences of the hop plant (Humulus lupulus L.) during the brewing process. In this study, we examined the anti-obesity effect of isomerized hop extract (IHE), which consists mainly of isohumulones. Supplementation of a high-fat diet with IHE reduced body weight gain and improved glucose tolerance in C57BL/6N and KK-A y mice. IHE also significantly decreased blood triglyceride and free fatty acid levels in these mice, suggesting that IHE is effective in preventing obesity and lowering the risk for CVD. Quantitative real-time PCR indicated that IHE up-regulated the expression of hepatic genes involved in peroxisomal and mitochondrial β-oxidation. These effects were very similar to those that follow administration of hypolipidemic drugs with the potential of activating the PPARα, and were not seen in PPARα-deficient mice. As well as IHE, purified isohumulone or isocohumulone clearly activated PPARα and γ in vitro and showed similar anti-diabetic and hypolipidemic effects in mice. Taken together, our results suggested that isohumulones may be potentially effective for the prevention of obesity, diabetes, and dyslipidemia in metabolic syndrome.

Electronic tongue as a screening tool for rapid analysis of beer

An electronic tongue (ET) comprising 18 potentiometric chemical sensors was applied to the quantitative analysis of beer. Fifty Belgian and Dutch beers of different types were measured using the ET. The same samples were analyzed using conventional analytical techniques with respect to the main physicochemical parameters. Only non-correlated physicochemical parameters were retained for further analysis, which were real extract, real fermentation degree, alcohol content, pH, bitterness, color, polyphenol and CO(2) content. Relationship between the ET and physicochemical datasets was studied using Canonical Correlation Analysis (CCA). Four significant canonical variates were extracted using CCA. Correlation was observed between 6 physicochemical variables (real extract and fermentation degree, bitterness, pH, alcohol and polyphenols' content) and 14 sensors of the ET. The feasibility of the ET for the quantification of bitterness in beer was evaluated in the aqueous solutions of isomerized hop extract and in the set of 11 beers with bitterness varying between 14 and 38 EBU (European Bitterness Units). Sensors displayed good sensitivity to isomerized hop extract and good prediction of the bitterness in beer was obtained. Calibration models with respect to the physicochemical parameters using ET measurements in 50 Belgian and Dutch beer samples were calculated by Partial Least Square regression. The ET was capable of predicting such parameters as real extract, alcohol and polyphenol content and bitterness, the latter with Root Mean Square Error of Prediction (RMSEP) of 2.5.

Use of Isomerized Hop Extract as a Replacement for Conventional Hop Extract and Its Influence on Beer Flavor

The procurement of raw materials has become an increasingly important factor for brewers. Depending on the crop year, not only malt, but also hops could be available in limited supply. Brewers using conventional hop products have limited options for reacting to this situation by optimizing their hopping formulations. One option for working around possible hop shortages might be the use of isomerized hop products. IKE (isomerized kettle extract) is one of the products that could be used as a replacement for CO2 hop extract. However, in addition to any financial benefits, it is essential to preserve the sensory characteristics of the beer. To obtain reliable data, extensive commercial-scale brewing trials were carried out. Analyses of hop products, wort, and beer samples were performed. Bitter compounds were quantified using specific (HPLC) and nonspecific (UV-spectro) methods. For hop aroma components, especially the compound linalool, which has a major impact on beer character, a method using GC-FID was applied for analyses of wort and beer samples. Samples were taken at different stages of wort boiling, which made it possible to obtain exact information about the solubilization of alpha- and iso-alpha-acids and the evaporation of hop aroma compounds during wort boiling. Beer samples were evaluated by a trained tasting panel. The trials demonstrated that IKE is a suitable kettle hop product that can be used to reduce hopping costs without affecting the sensory characteristics of a beer.

Isohumulones modulate blood lipid status through the activation of PPARα

Isohumulones derived from hops are the major bitter compounds in beer. It was recently reported that isohumulones activated peroxisome proliferator-activated receptors (PPARs) α and γ in vitro and modulated glucose and lipid metabolism in vivo. In this study, we examined the effects of isomerized hop extract (IHE) primarily containing isohumulones in C57BL/6N male mice and found that such treatment increased their liver weight and reduced their plasma triglyceride and free fatty acid levels. Microarray analysis and quantitative real time PCR (QPCR) showed that IHE dose-dependently upregulated the expression of a battery of hepatic genes that are involved in microsomal ω-oxidation and peroxisomal and mitochondrial β-oxidation. These effects were common in both genders and very similar to those found with the PPARα agonist, fenofibrate (FF). Moreover, these effects were not found in PPARα-deficient mice. Thus, our results strongly suggest that IHE intake upregulates the expression of key genes that are involved in hepatic fatty acid oxidation, and that it ameliorates the blood lipid profile by activating PPARα.

Dietary supplement of isohumulones inhibits the formation of aberrant crypt foci with a concomitant decrease in prostaglandin E2 level in rat colon

Male Fischer 344 rats were subcutaneously injected with azoxymethane (AOM) twice weekly at a dose of 15 mg/kg and were fed with freeze-dried (FD) samples of beer brewed without hops (non-hops beer), beer with hops at 4 times the amount of regular lager beer (x 4-hops beer), and isomerized hop extract (IHE) for the whole experimental period (I/PI) or for the post-initiation period (PI) only. Feeding FD beer samples at a dose of 1% significantly decreased the number of aberrant cryp foci (ACF) in the PI protocol over five weeks.x4-hops beer showed stronger inhibitory effects on the development of the numbers of aberrant crypts per focus and large ACF with four or more crypts than non-hops beer. Feeding IHE to rats at a dose of 0.01% or 0.05% in either the I/PI or PI experiment significantly reduced the numbers of ACF. Prostaglandin E2 (PGE2) levels in colonic mucosa of AOM-treated rats were significantly reduced by feeding of IHE. PGE2 production induced by lipopolysaccharide/interferon-gamma (LPS/IFN-gamma) in RAW264.7 cells was also reduced by treatment with IHE and isohumulone in a dose-dependent manner. These observations suggest that isohumulones show chemopreventive effects on ACF formation in rat colon by inhibiting the production of PGE2.

Prevention of diet-induced obesity by dietary isomerized hop extract containing isohumulones, in rodents

Isomerized hop extract (IHE), which consists mainly of isohumulones and is required in the beer brewing process, was investigated for its effects on diet-induced obesity in two strains of mice. C57BL/6N and KK-A(y) mice were fed a standard or high-fat diet containing IHE and their body and tissue weights were measured at various time points. Oral glucose tolerance tests (OGTT) and insulin tolerance tests (ITT) were carried out in high-fat diet-fed C57BL/6N mice. The effects of IHE on intestinal lipid absorption were examined in Wistar rats using a plasma triacylglycerol assay after oral administration of a lipid emulsion. Fecal lipid levels were also measured in these animals after they were fed a high-fat diet containing IHE for 15 days. The effects of IHE on pancreatic lipase activity and the expression of genes involved in hepatic lipid metabolism were also examined using an in vitro assay and quantitative RT-PCR, respectively. Supplementation of high-fat-containing chow with IHE reduced body weight gain and improved glucose tolerance in our experimental mice. A reduction in body weight gain was also observed in C57BL/6N mice fed a standard diet containing IHE. Wistar rats fed a high-fat diet containing IHE showed reduced plasma triacylglycerol levels and an increase in their fecal lipid excretion. Similarly, their pancreatic lipase activity was inhibited and their elevation in plasma triacylglycerol levels seen after the oral administration of lipid emulsion was significantly suppressed. IHE-fed mice showed an increased expression in their lipid oxidation genes and a decreased expression in genes involved in triacylglycerol biosynthesis. The inhibition of intestinal dietary fat absorption may be the mechanism by which IHE induces its weight-lowering effects in high-fat diet-fed mice. The modulatory effect of IHE on lipid metabolism may also, at least partly, be responsible for its beneficial effects on body weight gain. These results suggest that IHE may be helpful in humans in preventing diet-induced obesity and perhaps even metabolic syndrome, the latter of which is known to be associated with obesity.

Dietary isohumulones, the bitter components of beer, raise plasma HDL-cholesterol levels and reduce liver cholesterol and triacylglycerol contents similar to PPARα activations in C57BL/6 mice

The effects of dietary isohumulones, the main components accounting for the bitter taste of beer, on lipid metabolism were examined. Young female C57BL/6N mice were fed diets containing isomerized hop extract (IHE), which consists mainly of isohumulones. Administration of IHE with an atherogenic (high-fat and high-cholesterol) diet for 2 weeks resulted in a significant increase in plasma HDL-cholesterol (P<0.01), along with a concomitant reduction in the atherosclerosis index, an increase in liver weight and a decrease in body weight gain in a dose-dependent manner. When animals received IHE with either a cholesterol or a basal diet for 1 week, significant decreases in the liver content of cholesterol (P<0.01) and triacylglycerol (cholesterol diet, P<0.01) were observed. Quantitative analyses of hepatic mRNA levels revealed that IHE administration resulted in up-regulation of mRNA for acyl-CoA oxidase, acyl-CoA synthetase, hydroxymethylglutaryl-CoA synthetase, lipoprotein lipase and fatty acid transport protein, and down-regulation of mRNA for Apo CIII and Apo AI. Administration of purified isohumulones effectively resulted in the same changes as IHE. Administration of fenofibrate, an agonist for PPARalpha, with a cholesterol diet caused marked hepatomegaly, an increase in plasma HDL-cholesterol, a decrease in hepatic cholesterol content, and alterations in hepatic mRNA levels similar to those observed in mice given IHE. Taken together, these results suggest that the modulation of lipid metabolism observed in mice fed diets containing isohumulones is, at least in part, mediated by activation of PPARalpha.

Sensory and Analytical Characterisation of Reduced, Isomerised Hop Extracts and Their Influence and Use in Beer

The use of reduced, isomerised hop extracts became very popular during the last decade in terms of achieving both better foam and light stability. Today the most common products are those with tetra-hydro-iso-α-acids (THIA) or rho-iso-α-acids (RHIA). There is still not clarity concerning the taste properties of these products in comparison with iso-α-acid Bitter Units (BU). The experiments conducted showed that the bitter conversion factors determined in previous work (1.6 for THIA and 0.7 for RHIA) represented only perceived bitterness when presented in tap water. In the test beers a bitter conversion factor of 1.0–1.1 for THIA was determined and the factor of 0.7 for RHIA in beer was confirmed. Photometric methods led to considerable deviations when used for the determination of THIA and RHIA, whereas the HPLC method, in combination with either Solid Phase Extraction (SPE) or Liquid Liquid Extraction (LLE), led to very good results. RHIA was found to have a foam stabilising effect and it was also shown that the foam stabilising effect of THIA in unhopped beer was higher than in hopped beer. The quality of bitterness decreased with an increase of THIA and RHIA. A dependency on the alcohol content in regard to the bitter intensity was ascertained.