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The purpose of this study was to investigate the effect of alcoholic strength by volume (ASV) and storage conditions on turbidity in plum brandies. Different types of filter sheet were also tested for their effects on turbidity, as well as on the chemical composition and organoleptic characteristics of the distillates. The raw materials used were two plum distillates with initial ASVs of 76.77% v/v and 81.92% v/v. The distillates were diluted to alcohol contents of 37.5%, 40% and 50% v/v and stored under various conditions for 64 days. Filtration was performed using two depth filter sheets, with nominal retention rates of 0.40–0.48 μm and 0.80 μm, or with an activated carbon-based filter sheet. The lowest turbidity was observed in samples stored at ambient temperature with an ASV of 50% v/v. Reducing the alcohol content and storage temperature caused turbidity to increase. Samples prepared from distillate with an initial alcohol content of 76.77% v/v were characterized by significantly higher turbidity than those produced from spirit with an initial ASV of 81.92% v/v. Lowering the storage temperature resulted in a larger decrease in the concentration of volatile compounds after filtration. Use of an activated carbon filter sheet caused the greatest decrease in the majority of volatiles. Use of a filter sheet with a nominal retention rate of 0.80 μm led to the greatest improvement in the organoleptics of the tested plum distillates.

Mixed fermentation using Saccharomyces cerevisiae and non-Saccharomyces yeasts as starter cultures is well known to improve the complexity of wines and accentuate their characteristics. This study examines the use of controlled mixed fermentations with the Metschnikowia pulcherrima clade, Saccharomyces cerevisiae Tokay, and non-conventional yeasts: Wickerhamomyces anomalus and Dekkera bruxellensis. We investigated the assimilation profiles, enzyme fingerprinting, and metabolic profiles of yeast species, both individually and in mixed systems. The chemical complexity of apple wines was improved using the M. pulcherrima clade as co-starters. M. pulcherrima with S. cerevisiae produced a wine with a lower ethanol content, similar glycerol level, and a higher level of volatilome. However, inoculation with the Dekkera and Wickerhamomyces strains may slightly reduce this effect. The final beneficial effect of co-fermentation with M. pulcherrima may also depend on the type of fruit must.

Volatile sulfur compounds (VSCs) play an important role in the aroma profile of fermented beverages. However, because of their low concentration in samples, their analysis is difficult. The headspace solid-phase microextraction (HS&ndash, SPME) technique coupled with gas chromatography and mass spectrometry (GC&ndash, MS) is one of the methods successfully used to identify VSCs in wine and beer samples. However, this method encounters more obstacles when spirit beverages are analyzed, as the ethanol content of the matrix decreases the method sensitivity. In this work, different conditions applied during HS&ndash, SPME/GC&ndash, MS analysis, namely: ethanol concentration, salt addition, time and temperature of extraction, as well as fiber coating, were evaluated in regard to 19 sulfur compounds. The best results were obtained when 50/30 &mu, m Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS) was used to preconcentrate the analytes from the sample at 35 &deg, C for 30 min. The dilution of samples to 2.5% v/v ethanol and the addition of 20% w/v NaCl along with 1% EDTA significantly improves the sensitivity of extraction. The optimized method was applied to three fruit brandy samples (plum, pear, and apple) and quantification of VSCs was performed. A total of 10 compounds were identified in brandy samples and their concentration varied greatly depending on the raw material used from production. The highest concentration of identified VSCs was found in apple brandy (82 &micro, g/L).

The qualitative and quantitative profile of volatile compounds in agricultural distillate depends on numerous factors. Many such compounds, including higher alcohols, occur naturally, due to the metabolism of yeast during ethanol fermentation. Some are difficult to remove in the rectification process. For these reasons, it is desirable to reduce the synthesis of volatile compounds, among others higher alcohols, during the fermentation process. The results of the presented study showed that the raw materials, the method of starch liberation, and the initial pH of the sweet mashes affected the concentrations of higher alcohols in the distillates. Higher concentrations of 1-butanol, 1-propanol, and 2-propanol were found in distillates obtained from mashes prepared by the thermal-pressure method, while the remaining compounds occurred at higher concentrations in distillates obtained using the pressureless starch liberation method. The type of raw materials used had an influence on the concentration of the majority of higher alcohols. The content of 2-propanol, 2-methyl-1-propanol, 1-propanol, 1-butanol, 3-methyl-1-butanol, and 2-phenylethanol was lower in distillates obtained from mashes with an initial pH of 4, in comparison with those obtained from mashes with the pH set at 5.5.

This study investigates the effect of double- or single-stage distillation and different alcohol content in ‘hearts’ (middle fractions) on the distribution of aroma volatiles and undesirable compounds (methanol, hydrocyanic acid, ethyl carbamate) during distillation of plum brandies. Irrespective of the distillation method used, the first fractions (‘heads’) included mainly aliphatic aldehydes, acetals and esters as well as higher alcohols (1-propanol, 2-methyl-1-propanol, 1-butanol, 2-methyl-1-butanol and 3-methyl-1-butanol). Furfural, 1-hexanol, benzyl alcohol, 2-phenylethanol and ethyl carbamate occurred in relatively high concentrations in the ‘tail’ fractions. Increasing the concentration of alcohol in the heart fractions from 70 to 90% v/v resulted in a gradual decrease in the concentration of all detected volatile compounds. Compared with single-stage distillation, double distillation produced heart fractions with lower concentration of acetaldehyde and benzaldehyde and with higher contents of furfural and esters, such as isobutyl acetate and isoamyl acetate. There was a statistically significant increase in the amounts of methanol and ethyl carbamate obtained from double distillation compared with similar fractions derived from the single-stage process. However, in all fractions these compounds occurred in concentrations much lower than the limits specified by EU regulations. The heart fraction from the double-stage process with 83% v/v alcohol content received the best scores for aroma and flavour. Copyright © 2017 The Institute of Brewing & Distilling

The qualitative and quantitative composition of volatile compounds in fermented distillery mash determines the quality of the obtained distillate of agricultural origin (i.e., raw spirit) and the effectiveness of further purification steps. Propan-2-ol (syn. isopropyl alcohol), due to its low boiling point, is difficult to remove by rectification. Therefore, its synthesis needs to be limited during fermentation by Saccharomyces cerevisiae yeast, while at the same time controlling the levels of acetaldehyde and acetic acid, which are likewise known to determine the quality of raw spirit. Lactic acid bacteria (LAB) are a common but undesirable contaminant in distillery mashes. They are responsible for the production of undesirable compounds, which can affect synthesis of propan-2-ol. Some bacteria strains are able to synthesize isopropyl alcohol. This study therefore set out to investigate whether LAB with S. cerevisiae yeast are responsible for conversion of acetone to propan-2-ol, as well as the effects of the amount of LAB inoculum and fermentation parameters (pH and temperature) on the content of isopropyl alcohol, acetaldehyde, lactic acid and acetic acid in fermented mashes. The results of NMR and comprehensive two-dimensional gas chromatography coupled with time of flight mass spectrometry (GC × GC-TOF MS) analysis confirmed the ability of the yeast and LAB strains to metabolize acetone via its reduction to isopropyl alcohol. Efficient fermentation of distillery mashes was observed in all tested mashes with an initial LAB count of 3.34–6.34 log cfu/mL, which had no significant effect on the ethanol content. However, changes were observed in the contents of by-products. Lowering the initial pH of the mashes to 4.5, without and with LAB (3.34–4.34 log cfu/mL), resulted in a decrease in propan-2-ol and a concomitant increase in acetaldehyde content, while a higher pH (5.0 and 5.5) increased the content of propan-2-ol and decreased acetaldehyde content. Higher temperature (35 °C) promoted propan-2-ol synthesis and also resulted in increased acetic acid content in the fermented mashes compared to the controls. Moreover, the acetic acid content rose with increases in the initial pH and the initial LAB count.

This study set out to assess the acetone content in rye sweet mashes prepared using the thermal-pressure method of starch liberation, and to investigate the formation of 2-propanol during the fermentation process. In the first set of experiments, we evaluated the correlation between the color and the content of acetone and furfural in industrially produced sweet mashes (n = 37). The L * value was negatively correlated with the content of both acetone and furfural, while chromatic parameters a * and b * and the yellowness index (YI) had strong positive correlations with acetone (r &gt, 0.9) and furfural (r &gt, 0.8 for a * and r &gt, 0.9 for b * and YI). In the second set of experiments, we assessed the concentration of acetone and 2-propanol in distillery rye mashes, fermented by S. cerevisiae yeast and lactic acid bacteria. The influence of fermentation temperature on the formation of 2-propanol was also evaluated. The presence of 2-propanol in the post-fermentation media was confirmed, while a decrease in acetone content was observed. Fermentation temperature (27 &deg, C or 35 &deg, C) was found to have a significant effect on the concentration of 2-propanol in trials inoculated with lactic bacteria. The content of 2-propanol was more than 11 times higher in trials fermented at the higher temperature. In the case of yeast-fermented mashes, the temperature did not affect 2-propanol content. The acetone in the sweet mash was assumed to be a precursor of 2-propanol, which was found in the fermented mashes.

The character of plum brandies depends on a unique aroma profile of the plum and the microbiota present on the surface of the fruits, as well as yeast used for fermentation. In this study, an evaluation of the effect of microorganisms applied for the fermentation of Wegierka Zwykla var. plum mashes and processing temperature (18 °C, 30 °C) on its efficiency and volatile profile, as well as taste and flavour of distillates obtained was performed. An estimation of the odour activity values (OAVs) of the volatile compounds was also conducted. Regardless of whether the fermentation was carried out using Saccharomyces bayanus wine yeast or by native microflora present on plums as well as raisins, the efficiency of this process was high and ranged between 91.7 and 96.7% of the theoretical efficiency. Especially rich in esters (among others ethyl acetate and isoamyl acetate) was the distillate derived after fermentation with the microflora of plums and raisins, at 18 °C. An evaluation of the individual aromatic effect of chemical compounds present in tested distillates, in terms of their OAVs, revealed that the highest OAVs were reached with isovaleraldehyde. Other compounds that showed aroma values >1 and possibly had an effect on the overall aroma of tested plum distillates were the following: hexanal, benzaldehyde, ethyl acetate, isoamyl acetate, ethyl benzoate, ethyl hexanoate, 1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 1-hexanol. The performed sensory ranking showed that the best rated distillate was the one obtained after fermentation with the indigenous microflora of plums and raisins, at 18 °C. Copyright © 2016 The Institute of Brewing & Distilling

Production of electricity from wastewater in microbial fuel cells is possible due to the cooperation of hydrolytic, fermentative, and electrogenic microorganisms coexisting in a consortium. In this article, we present results that indicate that we can stimulate electrical current production from wastewater, from which power could not be produced without influencing the growth of a microbial consortium through preconditioning. The wood industry wastewater was thermally preconditioned at 45 °C before introducing it to microbial fuel cells which resulted in changing microbial consortium composition by the development of new species. In the anodes of microbial fuel cells that were fed preconditioned wastewater, we identified, by the means of metagenomic analysis, mixed fungi-bacteria syntrophic consortium that was capable of producing electricity from wood industry wastewater. The developed syntrophic consortium was dominated by fungi of the Trichocomaceae sp. and two bacteria species: Achromobacter insolitus and Geobacter sulfurreducens. None of these species were present in raw wastewater. Power was not generated in microbial fuel cells that were fed raw wastewater, but wastewater preconditioning stimulated power production at 0.33 W/m2 what responded to 1 A/m2 current density. The developed consortium decomposed cellulose present in wastewater into glucose and fermented it into acids and alcohols. We showed that stimulation of power production may be driven through substrate preconditioning before it is used in microbial fuel cells. By selecting growth conditions for a consortium, we may regulate its microbial composition and facilitate production of an electrical current from substrates that could not previously be used in microbial fuel cells.

In this study, we evaluate potato pulp waste as a potential raw material for obtaining yeast biomass. A portion of the carbohydrates in the potato pulp waste can thereby be converted into more valuable protein. The potato pulp waste was analyzed in terms of protein and ash content, dry mass, simple sugars, and starch content. Two kinds of hydrolysis were performed (thermo-acidic and enzymatic) to produce media for cultivating Candida guilliermondii and Pichia stipitis. The hydrolysates and post-cultivation leachates were analyzed by High Performance Liquid Chromatography (HPLC). The highest biomass yield after 48 h (39.3%) was noted for Candida guilliermondii yeast grown on enzymatic hydrolysate-based medium. Our results prove that potato waste pulp is a promising raw material for the production of yeast single-cell protein (SCP).

The study describes sulfuric acid pretreatment of straw from Secale cereale L. (rye straw) to evaluate the effect of acid concentration and treatment time on the efficiency of biofuel production. The highest ethanol yield occurred after the enzyme treatment at a dose of 15 filter paper unit (FPU) per gram of rye straw (subjected to chemical hydrolysis with 2% sulfuric acid (SA) at 121 &deg, C for 1 h) during 120 h. Anaerobic digestion of rye straw treated with 10% SA at 121 &deg, C during 1 h allowed to obtain 347.42 L methane/kg volatile solids (VS). Most hydrogen was released during dark fermentation of rye straw after pretreatment of 2% SA, 121 &deg, C, 1 h and 1% SA, 121 &deg, C, 2 h&mdash, 131.99 and 134.71 L hydrogen/kg VS, respectively. If the rye straw produced in the European Union were processed into methane, hydrogen, ethanol, the annual electricity production in 2018 could reach 9.87 TWh (terawatt-hours), 1.16 TWh, and 0.60 TWh, respectively.

This research shows the effect of dilute acid pretreatment with various sulfuric acid concentrations (0.5-2.0% [wt/vol]) on enzymatic saccharification and fermentation yield of rye straw. After pretreatment, solids of rye straw were suspended in Na citrate buffer or post-pretreatment liquids (prehydrolysates) containing sugars liberated after hemicellulose hydrolysis. Saccharification was conducted using enzymes dosage of 15 or 25 FPU/g cellulose. Cellulose saccharification rate after rye straw pretreatment was enhanced by performing enzymatic hydrolysis in sodium citrate buffer in comparison with hemicellulose prehydrolysate. The maximum cellulose saccharification rate (69%) was reached in sodium citrate buffer (biomass pretreated with 2.0% [wt/vol] H2 SO4 ). Lignocellulosic complex of rye straw after pretreatment was subjected to separate hydrolysis and fermentation (SHF) or separate hydrolysis and co-fermentation (SHCF). The SHF processes conducted in the sodium citrate buffer using monoculture of Saccharomyces cerevisiae (Ethanol Red) were more efficient compared to hemicellulose prehydrolysate in respect with ethanol yields. Maximum fermentation efficiency of SHF processes obtained after rye straw pretreatment at 1.5% [wt/vol] H2 SO4 and saccharification using enzymes dosage of 25 FPU/g in sodium citrate buffer, achieving 40.6% of theoretical yield. However, SHCF process using cocultures of pentose-fermenting yeast, after pretreatment of raw material at 1.5% [wt/vol] H2 SO4 and hydrolysis using enzymes dosage of 25 FPU/g, resulted in the highest ethanol yield among studied methods, achieving 9.4 g/L of ethanol, corresponding to 55% of theoretical yield.

This paper evaluated the effectiveness of nitric acid pretreatment on the hydrolysis and subsequent fermentation of Jerusalem artichoke stalks (JAS). Jerusalem artichoke is considered a potential candidate for producing bioethanol due to its low soil and climate requirements, and high biomass yield. However, its stalks have a complexed lignocellulosic structure, so appropriate pretreatment is necessary prior to enzymatic hydrolysis, to enhance the amount of sugar that can be obtained. Nitric acid is a promising catalyst for the pretreatment of lignocellulosic biomass due to the high efficiency with which it removes hemicelluloses. Nitric acid was found to be the most effective catalyst of JAS biomass. A higher concentration of glucose and ethanol was achieved after hydrolysis and fermentation of 5% (w/v) HNO3-pretreated JAS, leading to 38.5 g/L of glucose after saccharification, which corresponds to 89% of theoretical enzymatic hydrolysis yield, and 9.5 g/L of ethanol. However, after fermentation there was still a significant amount of glucose in the medium. In comparison to more commonly used acids (H2SO4 and HCl) and alkalis (NaOH and KOH), glucose yield (% of theoretical yield) was approximately 47–74% higher with HNO3. The fermentation of 5% nitric-acid pretreated hydrolysates with the absence of solid residues, led to an increase in ethanol yield by almost 30%, reaching 77–82% of theoretical yield.

This study investigates the effect of treatment with activated carbon and other adsorbents on the chemical composition and organoleptics of a barley malt-based agricultural distillate. Contact with activated carbon is one of the methods by which the quality of raw distillates and spirit beverages can be improved. Samples placed in contact with 1 g activated carbon (SpiritFerm) per 100 ml distillate with ethanol content of 50% v/v for 1 h showed the largest reductions in the concentrations of most volatile compounds (aldehydes, alcohols, esters). Increasing the dose of adsorbent to over 1 g 100 ml−1 did not improve the purity of the agricultural distillate significantly. Of the tested compounds, acetaldehyde and methanol showed the lowest adsorption on activated carbon. The lowest concentrations of these congeners (expressed in mg l−1 alcohol 100% v/v) were measured in solutions with ethanol contents of 70–80% v/v, while solutions with an alcoholic strength by volume of 40% did not show statistical...

This study investigates the effect of ageing on the qualitative and quantitative composition of plum distillate in contact with oak wood chips. Maturation was performed with lightly toasted French oak (Quercus sessiflora and Quercus robur) chips or oak chips made from fragments of empty barrels that had been used for ageing cognac. The effects of oak chip dose, process temperature, ageing system (static or circulatory) and ultrasound treatment were assessed. Maturation of plum distillate samples with oak chips resulted in higher levels of extractable organics (including tannins) and colour changes, which were correlated with the type and dose of oak chips, and the conditions of maturation. The content of sugars such as glucose, xylose and arabinose also increased, depending on the conditions and type of oak chips. Degradation of lignin resulted in liberation of sinapaldehyde, syringaldehyde, coniferaldehyde and vanillin, with intensities depending on the applied parameters. In terms of volatiles, decreases in the concentration of higher alcohols and aliphatic aldehydes were observed in the majority of maturation experiments, while concentrations of furanic aldehydes increased depending on the type and dose of oak chips, as well as on the conditions of maturation. The quantities of esters such as ethyl acetate decreased in the majority of experimental variants, whereas concentrations of ethyl caproate, ethyl caprylate and ethyl caprate increased gradually. Some phenols and lactones were detected in all matured samples, with the lowest levels found in the samples aged with oak chips made from cognac barrels.

Sugar beet pulp, a byproduct of sugar beet processing, can be used as a feedstock in second-generation ethanol production. The objective of this study was to investigate the effects of pretreatment, of the dosage of cellulase and hemicellulase enzyme preparations used, and of aeration on the release of fermentable sugars and ethanol yield during simultaneous saccharification and fermentation (SSF) of sugar beet pulp-based worts. Pressure-thermal pretreatment was applied to sugar beet pulp suspended in 2% w/w sulphuric acid solution at a ratio providing 12% dry matter. Enzymatic hydrolysis was conducted using Viscozyme and Ultraflo Max (Novozymes) enzyme preparations (0.015–0.02 mL/g dry matter). Two yeast strains were used for fermentation: Ethanol Red (S. cerevisiae) (1 g/L) andPichia stipitis(0.5 g/L), applied sequentially. The results show that efficient simultaneous saccharification and fermentation of sugar beet pulp was achieved. A 6 h interval for enzymatic activation between the application of enzyme preparations and inoculation with Ethanol Red further improved the fermentation performance, with the highest ethanol concentration reaching26.9±1.2 g/L and86.5±2.1%fermentation efficiency relative to the theoretical yield.

The aim of this study was to evaluate the influence of different starch liberation and saccharification methods on microbiological contamination of distillery mashes. Moreover, the effect of hop α-acid preparation for protection against microbial infections was assessed. The quality of agricultural distillates was also evaluated. When applying the pressureless liberation of starch (PLS) and malt as a source of amylolytic enzymes, the lactic acid bacteria count in the mashes increased several times during fermentation. The mashes obtained using the pressure-thermal method and malt enzymes revealed a similar pattern. Samples prepared using cereal malt exhibited higher concentrations of lactic and acetic acids, as compared to mashes prepared using enzymes of microbial origin. The use of hop α-acids led to the reduction of bacterial contamination in all tested mashes. As a result, fermentation of both mashes prepared with microbial origin enzyme preparations and with barley malt resulted in satisfactory efficiency and distillates with low concentrations of aldehydes.

The objective of this study was to determine the efficiency of rye and barley starch hydrolysis in mashing processes using cereal malts as a source of amylolytic enzymes and starch, and to establish the volatile profile of the obtained agricultural distillates. In addition, the effects of the pretreatment method of unmalted cereal grains on the physicochemical composition of the prepared mashes, fermentation results, and the composition of the obtained distillates were investigated. The raw materials used were unmalted rye and barley grains, as well as the corresponding malts. All experiments were first performed on a semi-technical scale, and then verified under industrial conditions in a Polish distillery. The fermentable sugars present in sweet mashes mostly consisted of maltose, followed by glucose and maltotriose. Pressure-thermal treatment of unmalted cereals, and especially rye grains, resulted in higher ethanol content in mashes in comparison with samples subjected to pressureless liberation of starch. All agricultural distillates originating from mashes containing rye and barley grains and the corresponding malts were characterized by low concentrations of undesirable compounds, such as acetaldehyde and methanol. The distillates obtained under industrial conditions contained lower concentrations of higher alcohols (apart from 1-propanol) than those obtained on a semi-technical scale.

U radu je ispitan utjecaj dozrijevanja u kontaktu s hrastovim trijeskama na sastav i koncentraciju destilata šljive. Destilatu šljive su tijekom starenja dodane lagano pržene trijeske francuskog hrasta (Quercus sessiflora i Quercus robur) ili trijeske dobivene od starih bačava u kojima je odležao konjak. Ispitan je utjecaj količine dodanih trijeski, temperature, načina dozrijevanja (statičnog ili uz cirkulaciju) te primjene ultrazvuka. Dozrijevanjem destilata šljive u prisutnosti hrastovih trijeski povećala se količina ekstraktibilnih organskih spojeva (uključujući tanine) i promijenila boja destilata, u ovisnosti o vrsti i količini dodanih trijeski te uvjetima dozrijevanja. Koncentracija se šećera, kao što su glukoza, ksiloza i arabinoza, povećala ovisno o uvjetima dozrijevanja i vrsti trijeski. Razgradnjom lignina oslobođene su određene količine sinapaldehida, siringaldehida, coniferaldehida i vanilina, u ovisnosti o uvjetima pokusa. Od hlapljivih spojeva, koncentracija se viših alkohola i alifatskih (acikiličkih) aldehida u većem broju varijanti pokusa smanjila, dok se koncentracija furanskih aldehida, ovisno o vrsti i količini trijeski te uvjetima dozrijevanja, povećala. Koncentracija se estera, poput etilacetata u većem broju varijanti pokusa smanjila, a etil-kaproata, etil-kaprilata i etil- -kaprata postupno povećala. Neki su fenoli i laktoni pronađeni u uzorcima destilata nakon dozrijevanja, a najmanje su koncentracije tih spojeva pronađene u uzorcima destilata dozrelog u kontaktu s hrastovim trijeskama dobivenim od bačava u kojima je odležao konjak., This study investigates the effect of ageing on the qualitative and quantitative composition of plum distillate in contact with oak wood chips. Maturation was performed with lightly toasted French oak (Quercus sessiflora and Quercus robur) chips or oak chips made from fragments of empty barrels that had been used for ageing cognac. The effects of oak chip dose, process temperature, ageing system (static or circulatory) and ultrasound treatment were assessed. Maturation of plum distillate samples with oak chips resulted in higher levels of extractable organics (including tannins) and colour changes, which were correlated with the type and dose of oak chips, and the conditions of maturation. The content of sugars such as glucose, xylose and arabinose also increased, depending on the conditions and type of oak chips. Degradation of lignin resulted in liberation of sinapaldehyde, syringaldehyde, coniferaldehyde and vanillin, with intensities depending on the applied parameters. In terms of volatiles, decreases in the concentration of higher alcohols and aliphatic aldehydes were observed in the majority of maturation experiments, while concentrations of furanic aldehydes increased depending on the type and dose of oak chips, as well as on the conditions of maturation. The quantities of esters such as ethyl acetate decreased in the majority of experimental variants, whereas concentrations of ethyl caproate, ethyl caprylate and ethyl caprate increased gradually. Some phenols and lactones were detected in all matured samples, with the lowest levels found in the samples aged with oak chips made from cognac barrels.