Roasted Malt Research Articles

Unraveling the role of germination days on the aroma variations of roasted barley malts via gas chromatography-mass spectrometry based untargeted and targeted flavoromics.

Roasting imparts malts with an increased amount of hedonic aromas. However, the relationship between the production of roasted malts and the generation of characteristic malt aromas remains unclear. In this study, roasted barley malts (RM) were prepared from three consecutive germination days (3, 4, 5D), and the aroma profiles among RM and base malt were holistically compared via HS-SPME-GC-MS/O-based flavoromics. Furthermore, the wort color, free amino acids, reducing sugars, and fatty acids compositions were determined before-and-after roasting. Results showed that roasting could flatten variations of precursors regardless of germination days. Additionally, based on quantitation of 53 aromas, a PLS-DA model was applied to differentiate all malts by 17 aromas with VIP≥1. As for aroma harmony, RM with 4D-germination outstood due to a pleasant nutty note with the highest sweet-to-nutty index of 0.8. This work answers how germination days would impact the aroma of RM for the first time.

Unusual Profile of Thiol Precursors in Special Malts: First Evidence of Chemical Glutathione-/γGluCys- and CysGly-/Cys- Conversions

Polyfunctional thiols (PFTs) present in beers or in wines are known to be released by yeast, during fermentation, from bound forms originally found in raw materials. In the brewing field, huge amounts of S-conjugates have been evidenced in several dual-purpose hop varieties. Malt, however, being the major raw material of beer, could also be a significant contributor of PFTs to beer (cysteinylated, Cys- and glutathionylated, G- precursors of 3SHol already identified in a few samples of barley and malt). Forty-two barley malts from 2 to 1500 EBC and five other malted cereals were screened to characterize their thiol precursor profile (G- and Cys- as well as dipeptidic bound CysGly- and γGluCys- forms of 3SHol). First, it was confirmed that G-3SHol was ubiquitous reaching up to 320 µg/kg in some samples, whereas Cys-3SHol remained at a trace level of up to 13 µg/ kg. Moreover, for the first time, dipeptidic bound forms of 3SHol were evidenced in malt (up to 10 and 11 µg/kg for CysGly-3SHol and γGluCys-3SHol, respectively). In pale malts, the level of the CysGly- form was shown to be proportional to that of G-3SHol (in situ γGT during the malting process). This appeared to be no longer true for special malts (ranging from 5 to 45°EBC), whose CysGly-3SHol level correlated instead with Cys-3SHol (suspected chemical conversion from the dipeptide conjugate). As for γGluCys-3SHol, it was only found in the special barley malts (indicating another chemical break of the Cys-Gly bond, here on G-3SHol) and in malted rye, spelt, and wheat. No precursors were found in roasted malt.

Single-Molecule Real-Time Sequencing to Explore the Mycobiome Diversity in Malt.

ABSTRACTThis study determined the composition of fungal communities and characterized the enriched fungal species in raw and roasted malts via the third-generation PacBio-based full-length single-molecule real-time (SMRT) sequencing of the full-length amplicon of the internal transcribed spacer (ITS) region. In total, one kingdom, six phyla, 23 classes, 56 orders, 120 families, 188 genera, 333 species, and 780 operational taxonomic units (OTUs) were detected with satisfactory sequencing depth and sample size. Wickerhamomyces (56%), Cyberlindnera (15%), Dipodascus (12%), and Candida (6.1%) were characterized as the dominant genera in the raw malts, and Aspergillus (35%), Dipodascus (21%), Wickerhamomyces (11%), and Candida (3.5%) in the roasted malts. Aspergillus proliferans, Aspergillus penicillioides, and Wickerhamomyces anomalus represented the crucial biomarkers causing intergroup differences. Correlation analysis regarding environmental factors indicated that the water activity (aw) of the samples affected the composition of the fungal communities in the malts. In practice, special attention should be paid to the mycotoxin-producing fungi, as well as other fungal genera that are inversely correlated with their growth, to ensure the safe use of malt and its end products.IMPORTANCE Fungal contamination and secondary metabolite accumulation in agricultural products represent a global food safety challenge. Although high-throughput sequencing (HTS) is beneficial for explaining fungal communities, it presents disadvantages, such as short reads, species-level resolution, and uncertain identification. This work represents the first attempt to characterize the fungal community diversity, with a particular focus on mycotoxin-producing fungi, in malt via the third-generation PacBio-based full-length SMRT sequencing of the ITS region, aiming to explore and compare the differences between the fungal communities of raw and roasted malts. The research is beneficial for developing effective biological control and conservation measures, including improving the roasting conditions, monitoring the environmental humidity and aw, and effectively eliminating and degrading fungi in the industry chain according to the diverse fungal communities determined, for the safe use of malts and their end products, such as beers. In addition, the third-generation SMRT sequencing technology allows highly efficient analysis of fungal community diversity in complex matrices, yielding fast, high-resolution long reads at the species level. It can be extended to different research fields, updating modern molecular methodology and bioinformatics databases.

Mitigation of acrylamide formation during malt processing

In this study, addition of asparaginase and glycine were tested for mitigation of acrylamide in roasted malt. Free asparagine and reducing sugars increased during germination of barley. Increasing the roasting temperature increased rate of acrylamide formation and browning in malt. Application of asparaginase (3000 and 4000 ASNU/kg) and glycine (3000, 4000 and 5000 ppm) on green malt before kilning had a limiting effect on acrylamide formation at high roasting temperatures. Acrylamide levels decreased around 32% by application of asparaginase at the level of 4000 ASNU/kg. Acrylamide levels decreased around 22% by the application of glycine at the level of 5000 ppm. With the application of enzyme and glycine in combination, the decrease in acrylamide was around 50%. The colour of dark roasted malt samples was not affected from asparaginase treatment; however, application of glycine caused darker colour, probably due to the increased rate of the Maillard reaction. Overall, the results indicated that dark roasted malts with significantly lower acrylamide content can be produced by using asparaginase and glycine treatments.

Roasted Malt for Distilling: Impact on Malt Whisky New Make Spirit Production and Aroma Volatile Development

Scotch malt whisky is typically produced using lightly kilned malted barley that imparts a relatively subtle aroma to the final product. Recently, there has been increased interest in exploring the feasibility of using roasted malts during whisky production to control congener profile. Although roasted malts are used widely within the brewing industry to develop product color and aroma in beer, applications and challenges have not yet been established for whisky production. This study investigated a role for roasted malt as a tool to impact whisky volatile composition and the consequences of such use for production efficiency of whisky new make spirit. Pot still malt was roasted at laboratory scale (0–60 min at 80–220 °C) and incorporated into a grist (≤50% w/w) for production of new make spirit. The influence of roasting conditions on malt processing characteristics and the impact on the concentration of key roasted malt volatile compounds in distillate were assessed using response surface modelling. Concentration of aroma active pyrazines and furans increased in the distillate produced using roasted malts (particularly when using malt heated >150 °C). Key indicators of process efficiency such as wort fermentability and alcohol yield reduced as intensity of malt roasting increased. Process efficiency when using low proportions of roasted malt (10% w/w) was comparable to that when using only pot still malt, but distillate volatile profile still differed significantly.

POSSIBILITY OF IPA BEER PRODUCTION, AND ITS COMPARISON WITH THE STANDARD BREWERY BEER IN "BIRRA PEJA", IN PEJA

Based on management requirements for innovation and following the global trend with new beers, we have tried to do our best for a beer that has never been in our products before. To produce this new beer with us at the Birra Peja brewery, we used the same malt as for the production of our current and best-selling beer, light beer, known as pilsner. To have an acceptable result, we used special Roasted malt with pronounced aroma characteristics. We also went in combination with our usual malt for the production of pilsner beer. Malt baked by a special production procedure has a reddish sheen and typical aroma, which serves to intensify and stabilize the aroma. And we used four different hops, Aurora, Ella, Cascade, and Palisade, which are used in certain stages of production to give the required fat for this type of beer. Also, in fermentation, we used special Fermentis yeast of type safale T58, to make India Pale Ales (IPA) or our brand "IPA Peja". For this type of beer is used the method of European brewery convection EBC. During boiling, hops with pronounced characteristics for this type of beer are added to achieve the right amount of fat. After maturing, we filtered this beer in the candle filter with only one Hyflo cel coating.

A survey on thermal processing contaminants occurrence in dark craft beers

Craft beers manufactured by small local breweries are becoming increasingly popular throughout the world due to their unique composition, taste and flavor. However, the ingredients used in brewing might lead to thermal processing contaminants in the final product. Thus, the aim of this study was to evaluate the levels of acrylamide (AA), polycyclic aromatic hydrocarbons (PAHs) and 3-monochloropropane-1,2-diol (3-MCPD) in dark craft beers available in Poland and the Czech Republic. The samples were prepared using a modified QuEChERS method that had been optimized and validated in-house; they were then analyzed by gas chromatography-mass spectrometry (GC–MS) and high-performance liquid chromatography with a diode array detector (HPLC-DAD). The results showed that PAHs were found in most of the analyzed beer samples. The total sum of PAHs ranged from 6.43 to 26.93 μg kg−1; the highest level of PAH4 content was 2.79 μg kg−1. Only three beer samples were free of any heavy PAHs. 3-MCPD and AA were also detected in all the beers, reaching levels of 14.0 μg kg−1 and 363 μg kg−1, respectively. The levels of 3-MCPD and AA were significantly higher in Polish beers than in beers from the Czech Republic. Higher amounts of 3-MCPD were found in beers containing roasted malt. A risk assessment was conducted for 3-MCPD and PAHs; it indicated that consumption of the examined beer samples should not cause any risk to human health. However, due to the high levels of acrylamide, regular consumption of dark beers poses a serious threat to human health and therefore should be strictly limited.

Study of antioxidant activity and phenolic compounds of extracts obtained from different craft beer by-products

This work deals with the study of the in vitro antioxidant potential of aqueous extracts obtained from brewer's spent grain (BSG) and lees (BL) from four brewing craft beers. The effect of type of malt (base malts with different percentage of roasted malt (BSG1: 0%, BSG2: 7,2%, BSG3: 11,8% and BSG4: 16%) and hop added during brewing (BL1-3: boil hopping, BL4: boil and dry hopping)) on the antioxidant potential of extracts, was studied. Results for BSG showed that the higher the content in roasted malt, the lower DPPH, ABTS+ and TPC values were found in BSG extracts. Results for BL extracts showed that BL4 (boil and dry hopping) presented the highest TPC content. Gallic acid, 4-hydroxyphenil acetate, epicatechin and sinapic acid were the major compounds contributing to the total phenolic content in all BSG samples whereas large differences among groups were found regarding to these compounds for BL.

Modelling flavour formation in roasted malt substrates under controlled conditions of time and temperature

Drum roasted products are used to impart colour, flavour and mouthfeel to beers. Here we designed a laboratory-scale roaster (100 g batch size) capable of precise time-temperature control and investigated the impacts of time, temperature and roasting substrate (barley, pale malt or germinated green malt) on formation of 20 key odour active aroma volatiles. Principal Components Analysis (PCA) of flavour volatile data across 37 laboratory roasted and 6 commercial roasted products generated a product flavour space depicting the relationship between roasting conditions and concentrations of these 20 compounds. Response surface models were produced for aroma compound concentrations across the design space of roasting times and temperatures for each substrate. These clearly illustrate the impacts of substrate moisture content and prior history (e.g. whether germinated or germinated and kilned) on flavour formation. In low moisture substrates a steep increase in associated heterocyclic aroma compound production was noted at process temperatures >180 °C.

Xanthohumol in XERME®, a xanthohumol-enriched roasted malt extract, and protection of DNA from oxidative damage: evaluation of a health claim pursuant to Article 13(5) of Regulation (EC) No1924/2006.

Following an application from TA‐XAN AG, submitted for authorisation of a health claim pursuant to Article 13(5) of Regulation (EC) No 1924/2006 via the Competent Authority of Germany, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver an opinion on the scientific substantiation of a health claim related to xanthohumol in XERME ®, a xanthohumol‐enriched roasted malt extract, and protection of DNA from oxidative damage. The scope of the application was proposed to fall under a health claim based on newly developed scientific evidence. The food proposed by the applicant as the subject of the health claim is xanthohumol in XERME ®, a xanthohumol‐enriched roasted malt extract. The Panel considers that xanthohumol in XERME ®, a xanthohumol‐enriched roasted malt extract, is sufficiently characterised. The claimed effect proposed by the applicant is ‘helps to maintain the integrity of DNA and protects against oxidative damage in the cells of the body’. The Panel considers that protection of DNA from oxidative damage is a beneficial physiological effect. The only human study from which conclusions can be drawn for the scientific substantiation of the claim did not show an effect of xanthohumol in XERME ® on the protection of DNA from oxidative damage. In the absence of evidence for an effect of xanthohumol in XERME ® on the protection of DNA from oxidative damage, the studies provided by the applicant on the proposed mechanisms by which the food/constituent could exert the claimed effect were not considered by the Panel for the scientific substantiation of the claim. The Panel concludes that a cause and effect relationship has not been established between the consumption of xanthohumol in XERME ®, a xanthohumol‐enriched roasted malt extract, and protection of DNA from oxidative damage.

Effect of barley malt, chickpea and peanut on quality of Barley based beverage

The present investigation had been done to optimize the effect of barley malt on production of barley based beverage. Malting of barley was carried out by steeping the cleaned and bold grains in tap water at 16°C for 2-3 days. The steeped grains were also germinated at 16°C for 2-3 days and the grains showing optimum growth were sorted out and kilning was done at 60°C for 1 day. Different levels of malted grain (i.e. 0, 1, 2, and 4 %) in barley extract were optimized. It was found that addition of 4 g malt to the extract was found to be effective in decreasing the viscosity and avoiding the formation of gruel like structure. There was non significant sensory change found on addition of roasted malt grain. Amylase activity of malt significantly increased on increasing time and no reducing sugars resulted at 90°C. Nutritive value of malted beverage was improved over control. Total soluble solids (TSS), viscosity, protein, fat, reducing sugar and total sugar of malted beverage was significantly increased as compared to control. Malted beverage was more organoleptically acceptable than control. Final beverage was made with 4 g malt, 25 g bengal gram and 15 g peanut per extract from 100 g barley with addition of sugar to 17°brix and homogenizing for proper mixing was autoclaved. Thus, malting could be an appropriate food-based strategy.

High molecular weight compounds generated by roasting barley malt are pro-oxidants in metal-catalyzed oxidations

The roasting process and color development have been related to an increase of the antioxidant activity of roasted malts. However, roasting is also responsible for the development of high molecular compounds with a pro-oxidant effect, leading to increased levels of radicals in systems based on iron- and copper-catalyzed Fenton reactions. For this reason, the overall antioxidant and pro-oxidant properties of three malt types with different roasting degrees (pilsner, melano and black) were evaluated in a Fenton-based model beer system (5.8 % ethanol, v/v). Black malt exhibited 50 % lower radical quenching capacity compared with pale and melano malts, as determined by spin trapping and electron spin resonance detection. These differences were related to the degree of roasting and the development of high molecular weight browning compounds. High molecular weight compounds isolated from black malt wort (molecular mass in the range of 4 × 106 and 108 g mol−1) were responsible for an increase of radicals (approximately 40 %) in a Fenton reaction and were able to accelerate metal-catalyzed oxidation in a beer model, as shown by a decrease of almost 11 % of the dissolved oxygen. Although black malt was able to reduce the overall levels of radicals generated by the Fenton reaction, high molecular weight compounds had an opposite effect due to the reductive redox-cycling of the catalytic amounts of iron.

Flavour generation during commercial barley and malt roasting operations: A time course study

The roasting of barley and malt products generates colour and flavour, controlled principally by the time course of product temperature and moisture content. Samples were taken throughout the industrial manufacture of three classes of roasted product (roasted barley, crystal malt and black malt) and analysed for moisture content, colour and flavour volatiles. Despite having distinct flavour characteristics, the three products contained many compounds in common. The product concentrations through manufacture of 15 flavour compounds are used to consider the mechanisms (Maillard reaction, caramelisation, pyrolysis) by which they were formed. The use of water sprays resulted in transient increases in formation of certain compounds (e.g., 2-cyclopentene-1,4-dione) and a decrease in others (e.g., pyrrole). The study highlights rapid changes in colour and particularly flavour which occur at the end of roasting and onwards to the cooling floor. This highlights the need for commercial maltsters to ensure consistency of procedures from batch to batch.

Roasting of malt and xanthohumol enrichment in beer

The use of commercial roasted malts increases the content of the hop polyphenol xanthohumol (XN) in beer. This carrier effect is caused by high molecular melanoidins from roasted malt. Three roasting trials with different malts were performed in order to study the development of XN enrichment of wort and beer in laboratory and brewing trials. Different colour measurements, malt and flavour analysis, radical formation and antioxidative activity of selected samples were carried out. Furthermore, sensory tests of beers were conducted. During roasting the XN and isoxanthohumol enrichment in wort and beer rose with the roasting intensity of malt until it reached a maximum. The XN content in wort increased linearly with the colour of wort made from the malt samples. In PVPP-treated worts and in filtered beers, the XN content increased exponentially with the colour. After passing through a maximum, both the colour value and XN content in wort and beer decreased. Interestingly, the colour losses were more intensive than the losses of XN in worts and beers. The development of radical formation and the reducing power was linked during roasting. That means reducing groups of melanoidins are responsible for reducing power and prooxidative properties of malts. These functional groups of melanoidins are involved in the development of XN enrichment properties, because a linear correlation between these parameters was found. In conclusion, the roasting regimes showed potential for the development of special malt for the XN enrichment in beer- or malt-based beverages in late roasting stages. The use of this special malt brings more XN with less coloured malt in beer.

Degradation of 5-hydroxymethylfurfural during yeast fermentation

5-Hydroxymethyl furfural (HMF) may occur in malt in high quantities depending on roasting conditions. However, the HMF content of different types of beers is relatively low, indicating its potential for degradation during fermentation. This study investigates the degradation kinetics of HMF in wort during fermentation by Saccharomyces cerevisiae. The results indicated that HMF decreased exponentially as fermentation progressed. The first-order degradation rate of HMF was 0.693 × 10−2 and 1.397 × 10–2 min−1 for wort and sweet wort, respectively, indicating that sugar enhances the activity of yeasts. In wort, HMF was converted into hydroxymethyl furfuryl alcohol by yeasts with a high yield (79–84% conversion). Glucose and fructose were utilised more rapidly by the yeasts in dark roasted malt than in pale malt (p < 0.05). The conversion of HMF into hydroxymethyl furfuryl alcohol seems to be a primary activity of yeast cells, and presence of sugars in the fermentation medium increases this activity.

Thermal Volatile Generation in Barley Malt: Online MS Studies

A novel mass spectrometry (MS) technique for measuring volatile formation during the thermal treatment of malt or barley has been developed that enables the effects of factors such as temperature and humidity on the pathways of flavor formation to be monitored in real time. Barley malt was treated at temperatures of 105, 130, 155, and 180°C under both dry and humid conditions. The principal MS ions monitored in each case were assigned to specific malt volatile compounds using an off-line solid-phase microextraction-trapping– and GC–dual-MS technique. Authentic standards of these compounds were injected into the apparatus singly and in groups over a range of concentrations. A linear response was obtained for calibrations of heterocyclic compounds (furans, pyrazines, pyranones, etc.) in complex mixtures at concentrations relevant to those monitored during online experiments. Hence, the technique can yield quantitative data on the formation of many compounds that are important to the character of roasted malt products. Data are presented illustrating the application of the technique, and results are discussed with respect to the underlying chemical pathways. At 180°C, dry conditions favored formation of pyrazines and 2-furaldehyde (furfural), whereas humidification of the purge gas resulted in higher concentrations of Strecker aldehydes relative to these compounds.

Optimisation of specialty malt volatile analysis by headspace solid-phase microextraction in combination with gas chromatography and mass spectrometry

The objective of this study was to develop a technique for analysing 14 flavour components, relevant for specialty malts. Therefore, a method was developed for the analysis of these components in dry ground malt using headspace solid-phase microextraction coupled with gas chromatography and mass spectrometry. A procedure was optimised for the optimal amount of sample, fibre selection, extraction temperature and extraction time. Afterwards, the method was calibrated and validated by the quantification of the specialty malt flavour components in a colour, a caramel and a roasted malt.

Development and Correlation between the Organic Radical Concentration in Different Malt Types and Oxidative Beer Stability

An optimized version of the patented electron spin resonance spectroscopy method, using a novel internal standard (52Cr: MgO), was used to monitor the development of organic radicals during the malting process and the radical content in different commercial specialty malts. The temperature during the withering and kilning steps in malt production had a direct influence on the generation of stable organic radicals in the finished malt, whereby higher temperatures resulted in greater radical concentrations. The majority of organic radicals in pilsner malt were bound in the husk and, therefore, did not significantly transfer into the wort and subsequent beer. In roasted malts, the organic radicals were distributed more uniformly throughout the kernel. Furthermore, depending on the organic radical content and Maillard reaction products present in the endosperm of crystal and roasted malts, more oxidation reactions took place during the mashing, and there was higher radical formation during the wort boiling process. Consequently, the endogenous antioxidant potential value and sulfur dioxide content in the final beer were reduced. These results indicate that there is a direct link between organic radicals in the endosperm generated by the kilning temperature during the malting process and color as an indicator of Maillard reaction products and the oxidative stability of the resultant beer.

Free and bound 3-chloropropane-1,2-diol in coffee surrogates and malts

The levels are reported of the free 3-chloropropane-1,2-diol (3-MCPD), its bound forms, the recognised precursors of 3-MCPD, and the factors influencing its formation in 5 selected coffee surrogates and 18 malts in the Czech Republic. The coffee surrogates had the free 3-MCPD level in the range of &lt; 9.0 to 32 &amp;micro;g/kg while the highest amount was found in roasted barley. In malts, the free 3-MCPD levels were similarly low (&lt; 9.0 to 45 &amp;micro;g/kg) being the highest in roasted malts (16-45 &amp;micro;g/kg). Nevertheless, the values found in either surrogates or malts, calculated after normalisation to 40% dry matter content, did not exceed the European Union limit of 20 &amp;micro;g/kg adopted for soy sauces and acid-HVP. The risk for consumers could arise from the bound 3-MCPD, its elevated levels having been found in both coffee surrogates and malts. In coffee surrogates, the bound 3-MCPD levels varied between 145&amp;minus;1184 &amp;micro;g/kg product; the highest level was found in roasted barley. The bound 3-MCPD levels exceeded the free 3-MCPD levels 32 to 81 times. In malts, the bound 3-MCPD levels ranged from 4.0&amp;minus;650 &amp;micro;g/kg, the highest amount having been found in roasted malts (463&amp;minus;650 &amp;micro;g/kg). The bound 3-MCPD levels exceeded the free 3-MCPD levels 0.4 to 36 times.

Antioxidant Properties of Kilned and Roasted Malts

Compounds possessing antioxidant activity play a crucial role in delaying or preventing lipid oxidation in foods and beverages during processing and storage. Such reactions lead to loss of product quality, especially as a consequence of off-flavor formation. The aim of this study was to determine the antioxidant activity of kilned (standard) and roasted (speciality) malts in relation to phenolic compounds, sugars, amino acids, and color [assessed as European Brewing Convention units (degrees EBC) and absorbance at 420 nm]. The concentrations of sugars and amino acids decreased with the intensity of the applied heat treatment, and this was attributed to the extent of the Maillard reaction, as well as sugar caramelization, in the highly roasted malts. Proline, followed by glutamine, was the most abundant free amino/imino acid in the malt samples, except those that were highly roasted, and maltose was the most abundant sugar in all malts. Levels of total phenolic compounds decreased with heat treatment. Catechin and ferulic acid were the most abundant phenolic compounds in the majority of the malts, and amounts were highest in the kilned samples. In highly roasted malts, degradation products of ferulic acid were identified. Antioxidant activity increased with the intensity of heating, in parallel with color formation, and was significantly higher for roasted malts compared to kilned malts. In kilned malts, phenolic compounds were the main identified contributors to antioxidant activity, with Maillard reaction products also playing a role. In roasted malts, Maillard reaction products were responsible for the majority of the antioxidant activity.