Analysis of volatile compounds in L. edodes blanched by hot water and microwave

The comprehensive flavour characterisation and volatile compounds of raw L. edodes, hot water blanching (HB) sample and microwave blanching (MB) sample were comparatively analysed by electronic nose technology and headspace solid‐phase micro‐extraction combined with gas chromatography‐mass spectrometry (HS‐SPME‐GC‐MS). Results indicated that volatile components in L. edodes markedly changed after HB and MB. Volatile compounds of raw L. edodes consisted mainly ketones, sulphide and alcohols, and 3‐octanone, as well as 1‐octen‐3‐one, were the major compounds. The content of ketones and sulphides in blanched samples markedly decreased, while the relative content of aldehydes, hydrocarbons and esters increased, which became the major volatile compounds of treatment samples. In addition, the percentage contents of esters, alcohols and sulphides in MB samples were significantly (P < 0.05) higher than that in HB samples, especially 1‐octen‐3‐ol, which contributes more to mushroom flavour. Therefore, MB is a better pretreatment method of L. edodes processing and cooking according to the results of experiment.     

Manipulation of volatile compound transformation in durian wine by nitrogen supplementation

This study evaluated the impact of added diammonium phosphate (DAP) and a L‐leucine‐L‐phenylalanine mixture (Leu+Phe) on durian wine fermentation by Saccharomyces cerevisiae var. bayanus EC‐1118. Changes in yeast cell population, ^oBrix, sugars, organic acids and pH were similar in all fermentations, regardless of nitrogen supplementation at a concentration of 150 mg N L^?1. The supplementation of Leu+Phe accelerated the utilisation and reduced the formation of volatile sulphur compounds such as diethyl disulphide, ethyl thioacetate and 2‐(ethylthio)ethanol, which were 64.3%, 26.0% and 48.4% lower than the control, respectively. Nevertheless, the supplementation of Leu+Phe heightened the production of isoamyl alcohol, 2‐phenylethyl alcohol and their corresponding esters, especially isoamyl acetate was 1.6 times and 2‐phenylethyl acetate was 26.5 times higher than the control. The supplementation with DAP exerted negligible effects on the volatile composition. The results of this study suggest that the addition of specific amino acids may be a novel approach to manipulating durian wine flavour by suppressing or accentuating the formation of certain aroma compounds.     

Influence of exopolysaccharide‐producing cultures on the volatile profile and sensory quality of low‐fat Tulum cheese during ripening

The objective of this investigation was to compare the composition and changes in the concentration of volatiles in low‐fat and full‐fat Tulum cheeses during ripening. Tulum cheese was manufactured from low‐ or full‐fat milk using exopolysaccharide (EPS)‐producing or non‐EPS‐producing starter cultures. A total of 82 volatile compounds were identified belonging to the following chemical groups: acids (seven), esters (21), ketones (14), aldehydes (six), alcohols (14) and miscellaneous compounds (20). The relative amounts of acids, alcohols and aldehydes increased in the cheeses made with EPS‐producing cultures during 90 days of ripening. Differences were found in the volatile profile of full‐fat Tulum cheese compared with the low‐fat variant, especially after 90 days of ripening. Exopolysaccharide‐producing cultures changed the volatile profile, and the EPS‐producing cultures including Streptococcus thermophilus + Lactobacillus delbrueckii subsp. bulgaricus + Lactobacillus helveticus (LF‐EPS2) produced cheese with higher levels of methyl ketones and aldehydes than the non‐EPS cultures. In the sensory analysis, full‐fat Tulum cheeses and the cheese produced with the EPS‐producing culture containing Lb. helveticus (LF‐EPS2) were preferred by the expert panel. It was concluded that the use of EPS‐producing starter cultures in the manufacture of low‐fat Tulum cheese had the potential to improve the flavour.     

Microbiological and Physicochemical Analysis of Pumpkin Juice Fermentation by the Basidiomycetous Fungus Ganoderma lucidum

A new protocol for processing of pumpkin juice was set up which included fermentation by the basidiomycete Ganoderma lucidum at 28 °C for 7 d. The growth curve of G. lucidum in pumpkin juice was successfully (R² = 0.99) fitted by a 4‐parameter logistic model and the ideal highest biomass was estimated to be 4.79 g/L. G. lucidum was found to have a significant acidification effect on pumpkin juice. The lowest pH (4.05 ± 0.05) and highest total titratable acidity (14.31 ± 0.16 mL 0.1 M NaOH/100 mL) were found on the 4th day during fermentation. Sugars in pumpkin juice fermented with G. lucidum showed a significant decrease, especially glucose and fructose. On the contrary, the release of exo‐polysaccharides and free amino acids greatly enriched the pumpkin juice. The variation of color index and viscosity also mirrored the above behavior. Based on headspace solid phase microextraction and gas chromatography‐mass spectrometry, 68 volatile compounds were identified, including 17 esters, 14 alcohols, 13 phenyl compounds, 11 aldehydes, 8 ketones, 3 acids, 1 furan, and 1 benzothiazole. The pumpkin juices fermented for different days were markedly differentiated with principal component analysis and the fermentation process was tentatively divided into 3 periods: the booming (from the 1st to 4th day), steady (from the 5th to 6th day), and decline (the 7th day) period.     

Potential of lactic acid bacteria to improve the fermentation and quality of coffee during on‐farm processing

This study describes, for the first time, the potential use of selected lactic acid bacteria (LAB) to conduct improved coffee bean fermentation during on‐farm wet processing. Among different strains tested, Lactobacillus plantarum LPBR01 showed a suitable production of organic acids and flavour‐active esters in a coffee‐pulp simulation medium and was used as starter culture under field conditions. The results indicated that L. plantarum LPBR01 was able to establish an accelerated coffee‐pulp acidification process and potentially reduced the fermentation time from 24 to 12 h. The inoculation of LPBR01 strain also increased significantly the formation of volatile aroma compounds during fermentation process (such as ethyl acetate, ethyl isobutyrate and acetaldehyde) and enabled the production of beverage with distinct sensory notes and a remarkable increase in quality compared to the conventional process. Our results suggest that the use of LAB in coffee processing is an ideal alternative way to conduct faster and improved coffee bean fermentation.     

Volatile composition and nutritional quality of the edible mushroom Polyporus tenuiculus grown on different agro‐industrial waste

The volatile composition and the nutritional value of Polyporus tenuiculus grown on supplemented and nonsupplemented wheat straw and willow sawdust were determined. Thirty‐nine volatile compounds were detected, including acids, esters, alcohols, hydrocarbons, aldehydes and ketones. The main volatile compound in all samples was 1‐octen‐3‐ol, with increasing levels in mushrooms cropped on supplemented substrate. In addition, several precursors of this alcohol were identified in lower percentages. Mushrooms grown on supplemented substrates showed lower fat (5.2–5.7%) and carbohydrate contents (48.2%) and higher protein content (22–22.5%). Fibre and ash contents showed some variations between types of substrates. Compared to other edible fungi, P. tenuiculus high fibre and protein contents point to this species as a healthy nutritional alternative of interest for the food industry. Moreover, the wide spectrum of volatile compounds of P. tenuiculus reveals great potential for biotechnological applications such as the production of “non artificial” mushroom flavour.     

Isolation and identification of a black Aspergillus strain and the effect of its novel protease on the aroma of Moutai‐flavoured liquor

Among Chinese traditional distilled liquors, Moutai‐flavoured liquor is the most famous, owing to its complicated process as it is derived from fermented sorghum coupled with the use of a Moutai‐flavoured Daqu. In this study, a novel isolate, belonging to a black Aspergillus, was obtained and identified as Aspergillus hennebergii by ITS‐5.8S rRNA sequencing analysis and conventional morphologic identification. The influences of initial pH, carbon source, nitrogen source and metal ions on the production of an A. hennebergii protease were studied. The results revealed that metal ions exerted a significant effect on enzyme production and activity. Additionally, the potential application of the protease from A. hennebergii was investigated. The enzymatic hydrolysis resulted in the identification and quantification of 42 compounds, including alcohols, aldehydes, pyrazines and esters. These volatile compounds exhibited special flavour properties. Significant differences were observed between the enzyme treatments and the control sample. Samples from the enzyme treatments led to the highest amounts of alcohols, pyrazines and aromatics. These results suggest that A. hennebergii, or its protease, may have some application values for the enhancement of the quality of Chinese liquor and for the improvement of the liquor production process. Copyright © 2014 The Institute of Brewing & Distilling     

The development of free amino acids and volatile compounds in cheese ‘Oloumoucké tvarůžky’ (PGI) during ripening

Twenty‐two free amino acid (FAA) concentrations were observed during manufacture (7 days) and ripening period (42 days follow‐up) of Olomoucké tvar??ky (PGI, smear acid cheese). During the ripening period, the amounts of volatile compounds and selected sensory attributes were also analysed. The free amino acids were determined by means of ion‐exchange chromatography, and the volatile compounds were detected and identified using HS‐SPME coupled with GC/MS method. The development of the individual FAA content positively correlated with the ripening period (r = 0.7734–0.9229; P < 0.01). Forty‐six volatile compounds (14 alcohols; 10 esters; 7 ketones; 5 acids; 4 aldehydes; 3 sulphur compounds; 2 phenol compounds; and 1 terpene) were identified. Concentrations of several compounds increased (e.g. 3‐methylbutanal, 2‐butanol, 2‐butanone; P < 0.05) or decreased (e.g. dimethyldisulphide, methanethiol, 2‐phenylethylacetate, methylbutyric acid; P < 0.05) over cheese ageing. The results gave information about the development of sensory active substances and its precursors in Olomoucké tvar??ky during ripening. In conclusion, we found that free amino acid concentrations and sulphur compounds are positive with improved flavour.     

Characterisation of physicochemical properties,flavour components and microbial community in Chinese Guojing roasted sesame-like flavour Daqu

Daqu is a saccharifying and fermentation agent for Baijiu production. It provides ingredients, flavours or flavour precursors, microorganisms and enzymes that influence Baijiu quality and character. Here, a systematic investigation was performed on the physicochemical properties, volatile flavour compounds and microbial community structures of Chinese Guojing roasted sesame-like flavour Daqu. The results show that the Daqu exhibited high saccharifying ability, but low liquefying and fermenting ability. Analysis by headspace solid-phase microextraction gas chromatography–mass spectrometry showed that the Daqu and a simulated solid-state fermentation sample contained 28 and 49 volatile components, including alcohols, esters, aldehydes, benzodiazepines, alkenes and nitrogen containing compounds. The main volatiles were aldehydes, esters and alcohols in Daqu, while the esters, alcohols and phenols were relatively higher in the solid-state fermentation sample. With the microbial flora, Bacillus, Actinobacteria_norank, Thermoactinomyces, Enterobacteriaceae_norank, Enterobacter, Actinopolyspora, Kroppenstedtia, Pseudomonas and Sphingobium were the main prokaryotic microorganisms. The dominant fungi were Thermomucor, Trichocomaceae_Incertae Sedis, Absidia, Eurotiomycetes_Incertae Sedis, Mucorales_Incertae Sedis and Eurotiales_Incertae Sedis. By systematically characterising the physicochemical properties, flavour compounds and microorganisms in Daqu, this study increases the understanding of Daqu and provides information for improvements in Baijiu production and quality. © 2019 The Institute of Brewing & Distilling     

Characteristics of aromatic compound production using new shochu yeast MF062 isolated from shochu mash

The effect of temperature on the production of aromatic compounds using Heisei Miyazaki yeast MF062 was compared between 10 industrial yeasts. All yeasts tested produced characteristic patterns of alcohols and esters in fermentation tests with rice‐koji at 20, 28 and 38°C. The concentration and composition in mature moromi with rice‐koji at 20, 28 and 38°C were almost the same as those with barley‐koji. Therefore, it was suggested that fermentation temperature is an important factor in the production of aromatic compounds. MF062 produced almost the same concentration of β‐phenethyl alcohol at both 38 and 28°C. The concentration was higher than that generated by the other 10 yeasts. MF062 produced higher concentrations of i‐butyl alcohol than the other yeasts at higher fermentation temperatures. Moreover, compared with the other yeasts, MF062 produced a lower concentration of acetate, which can give an off‐flavour in excess concentrations in shochu. The production of acetoin was divided into two groups – a high producing group and a low producing group – at all temperatures. MF062 belonged to the latter group and showed preferred characteristics in the production of shochu, resulting in a high concentration of preferred aromatic compounds and a low concentration of compounds that impart an off‐flavour. Copyright © 2013 The Institute of Brewing & Distilling     

Effect of autochthonous starter cultures on the volatile flavour compounds of Chinese traditional fermented fish (Suan yu)

Effect of autochthonous starter cultures on the volatile flavour compounds of Chinese traditional fermented fish was studied. Lactobacillus plantarum 120, Staphylococcus xylosus 135 and Saccharomyces cerevisiae 31, isolated from Suan yu, were selected as starter cultures. Volatiles were extracted by headspace solid‐phase microextraction (SPME) and analysed by gas chromatography–mass spectrometry technology (GC‐MS). Esters and alcohols were the main components of volatiles, accounting for over 50 percentage points in all samples. The highest content of esters (3034.54 μg kg^?1) was observed in S1 inoculated with L. plantarum 120, while the highest content of alcohols (2164.53 μg kg^?1) and ketones (379.98 μg kg^?1) was detected in S3 inoculated with S. cerevisiae 31. The content of acids and aldehydes was lower in inoculated samples. Principal component analysis revealed that the volatile composition was primarily influenced by the nature of the starter cultures. L. plantarum 120 and S. xylosus 135 could accelerate fermentation.     

Effects of cofermentation and sequential inoculation of Saccharomyces bayanus and Torulaspora delbruckii on durian wine composition

This work investigated the effects of cofermentation and sequential inoculation of Torulaspora delbrueckiiBiodiva and Saccharomyces bayanusEC‐1118 on chemical and volatile components of durian wines. Cofermentation and sequential inoculation resulted in higher production of ethanol (6.2% and 7.7% v/v, respectively) relative to the control (5.3% for S. bayanus and 5.8% for T. delbrueckii). Further, cofermentation and sequential inoculation produced higher amounts of acetyl esters and higher alcohols especially isoamyl alcohol and 2‐phenylethyl alcohol than monoculture fermentation. Most endogenous sulphur volatiles, especially disulphides that impart a character‐impact durian odour, declined to trace levels, but new ones such as thioesters were formed. Sulphur volatiles in the durian wines fermented by cofermentation and sequential inoculation accounted for 0.03% and 0.05% of total peak area. The study suggests that the use of S. bayanus in conjunction with non‐Saccharomyces such as T. delbrueckii may improve the aromatic intensity and complexity of durian wine.     

Potential impact of dairy yeasts on the typical flavour of traditional ewes' and goats' cheeses

The contribution of Debaryomyces hansenii, Kluyveromyces lactis and Kluyveromyces marxianus strains to the typical flavour of traditional ewes' and goats' cheeses was assessed. Fourteen yeast strains were grown in liquid medium mimicking cheese composition and volatile compounds were identified by gas chromatography-mass spectrometry. Yeasts were able to produce key volatile compounds characteristic of the cheeses from which they were isolated. Inter-species and inter-strain variations were observed. Under the conditions tested, D. hansenii produced the lowest levels of volatile compounds, with large intra-strain variations. Kluyveromyces strains primarily produced esters and alcohols. K. marxianus strains were associated with the production of acids, ethyl decanoate, 1-propanol and benzaldehyde, whereas K. lactis was correlated with the presence of ketones, ethyl acetate and secondary alcohols. In conclusion, this study shows the heterogeneous potential of dairy yeasts to contribute to final cheese flavour.     

Microbial succession and metabolite changes during the fermentation of Chinese light aroma‐style liquor

A combination of culture‐dependent and culture‐independent methods and SPME–GC–MS were used to monitor changes of bacterial and yeast communities, and flavour compounds during the fermentation process of Chinese light aroma‐style liquor. Bacillus and Lactobacillus were the main bacterial genera. Pichia anomala, Saccharomyces cerevisiae and Issatchenkia orientalis were the dominant yeast species. There was a close relationship between fermentation time and the shift of microbial community. Compared with the microbiota in the fermentation of other style liquors, higher bacterial diversity and different non‐Saccharomyces composition led to a variety of metabolites. Metabolite analysis showed that esters, acids, alcohols, aromatic compounds and phenols were the main flavour components and most of them were synthesised in the latter phase of fermentation. Principal component analysis further demonstrated that Bacillus and yeast were the most influential microorganisms in the first 10 days of fermentation, and lactic acid bacteria predominated in the later phase. Lactic acid bacteria regulated the composition of other bacteria and yeast, and synthesised flavour compounds to affect the organoleptic properties of liquor. S. cerevisiae and P. anomala were two important yeast species responsible for the characteristic aroma of liquor. These results present a comprehensive understanding of microbial interaction and potential starter cultures to produce desirable liquor quality. © 2018 The Institute of Brewing & Distilling     

Utilisation possibility of Enterococcus faecalis isolates from neonate's faeces for production of fermented sausages as starter cultures

This study aimed at assessing the utilisation possibility of Enterococcus faecalis as starter cultures for production of fermented sausages. The E. faecalis isolates isolated from faeces samples of 5‐day‐old healthy newborn babies, identified by 16SrDNA sequencing and free from virulence determinants as proven by genomic sequencing, were used for fermented sausages production as starter culture. Six treatments (four inoculated with four different E. faecalis isolates, one with commercial starter culture and one control) were prepared. The inoculation with E. faecalis showed a stronger acidification compared with the control. The treatments with E. faecalis showed significantly higher flavour and acceptability scores in comparison with the control or commercial starter culture. Both of commercial starter culture and E. faecalis were positive with tyramine. Apart from the amine production, the inoculation with E. faecalis generally improved the acidifying activity and flavour of the products, suggesting their application potentials in fermented sausages production as starter cultures.     

Effects of nitrogen catabolite repression‐related amino acids on the flavour of rice wine

The quality of rice wine is highly dependent on the content of the flavour compounds produced by the budding yeast Saccharomyces cerevisiae. In this study, the effects of three amino acids (arginine, glutamate and glutamine) related to nitrogen catabolite repression on the formation of flavour compounds were investigated. Each of these amino acids could promote the growth of S. cerevisiae, and a total of 83 flavour compounds were found in a model system of rice wine production. The effects of arginine, glutamate and glutamine on the content of the higher alcohols, amino acids and esters were significant, whereas the effects on the aldehydes and organic acids were slight. The results of this study could facilitate the development of new strategies to control the flavour pattern and improve the quality of rice wine. Copyright © 2015 The Institute of Brewing & Distilling     

Optimization of alcohol‐free beer production by lager and cachaça yeast strains using response surface methodology

Alcohol‐free beers (AFBs) are an attractive segment of the beer market both for the brewing industry and for consumers. While AFBs produced by arrested/limited fermentation often suffer from a lack of volatile compounds, beer flavour can be improved by yeast selection and optimization of fermentation conditions. The yeast selection strategy was demonstrated by comparing traditional lager yeast with selected cachaça yeast strains. Correspondingly, response surface methodology was used to enhance the formation of the flavour‐active volatile compounds by optimization of the fermentation conditions (original wort extract, fermentation temperature, pitching rate). Statistical analysis of the experimental data revealed the relative significance of process variables and their interactions. The developed quadratic model describing the responses of total esters and higher alcohols to changes in process variables was used to predict the ideal fermentation conditions in terms of flavour formation. The predicted conditions were experimentally verified and alternative strategies of AFB production are suggested. Copyright © 2016 The Institute of Brewing & Distilling     

The effect of distillation conditions and alcohol content in ‘heart’ fractions on the concentration of aroma volatiles and undesirable compounds in plum brandies

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     

Physicochemical profile and determination of volatile compounds in cachaça stored in new oak (Quercus sp.), amburana (Amburana cearensis), jatoba (Hymenaeae carbouril), balsam (Myroxylon peruiferum) and peroba (Paratecoma peroba) casks by SPME‐GC–MS

Aging has become common practice among producers seeking to increase the value of their products. The objective of this work was to conduct periodic monitoring by solid‐phase microextraction–gas chromatography–mass spectrometry of the physical and chemical quality of aging cachaça in terms of the alcohol content, volatile acidity, esters, aldehydes, higher alcohols, furfural, methanol, dry extract, copper and volatile compounds in the production process (distilled fractions) and during storage in casks newly made from oak (Quercus sp.), amburana (Amburana cearensis), jatoba (Hymenaeae carbouril), balsam (Myroxylon peruiferum) and peroba (Paratecoma peroba). The barrels were made in a specialized cooperage, and cachaça was obtained from a production unit in the southern region of Minas Gerais. Distinct physicochemical values were obtained for the distilled fractions; head and tail fractions had inappropriate concentrations of alcohol, aldehydes and butan‐1‐ol. Values within the limits established by law were obtained for the heart fraction, both in the distillation process and during aging, and it is, therefore, suitable for consumption. Several important compounds responsible for the aroma and flavour of the cachaças were observed, and alcohols, acids, esters and sesquiterpenes were found to compose the main groups. Through variance and main component analysis, important chemical changes were observed in the beverages. Copyright © 2016 The Institute of Brewing & Distilling     

Evolution of volatile compounds in papaya wine fermented with three Williopsis saturnus yeasts

The changes in volatile compounds during papaya juice fermentation with three Williopsis saturnus yeasts were investigated in this study. Time‐course papaya juice fermentations were carried out using three Williopsis saturnus yeasts: W. saturnus var. mrakii NCYC2251, W. saturnus var. saturnus NCYC22 and W. saturnus var. sargentensis NCYC2727. Changes in yeast cell population, Brix and pH were similar among the three yeasts, which preferentially utilised glucose over fructose while partially degrading l ‐malic acid. A range of volatile compounds were produced during fermentation including fatty acids, alcohols and esters with esters being the most abundant volatile compounds produced. Benzyl isothiocyanate, butyric acid, 2‐ethylhexanol, benzaldehyde and β‐damascenone present in the papaya juice were metabolised to trace levels during fermentation. There were significant variations among the three yeasts in their ability to produce and metabolise volatile compounds during fermentation. The study suggests that papaya juice fermentation with W. saturnus yeasts is able to result in the formation of a more complex aroma compounds.