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     

Characteristics of immobilised β‐glucosidase and its effect on bound volatile compounds in orange juice

In this study, bound volatile compounds were isolated and extracted with Amberlite XAD‐2 resin and then hydrolysed by free or immobilised β‐glucosidase. The released bound volatiles were analysed by GC‐MS. In addition, the optimisation of immobilisation method on sodium alginate and the characteristics of immobilised β‐glucosidase were studied. The results showed that crosslinking‐entrapment was the best method. The optimal conditions of this method were as follows: sodium alginate concentration 3.5%, glutaraldehyde concentration 1%, crosslinking time 3 h, immobilisation time 2 h and CaCl₂ concentration 3%. The optimum temperature for β‐glucosidase (65 °C) was decreased by 10 °C after immobilisation, while the optimum pH values for free and immobilised β‐glucosidase were both at pH 5.0. The K_m values of free and immobilised β‐glucosidase were 14.89 and 0.59 m , respectively. In total, thirteen and six bound volatile compounds were detected in orange juice hydrolysed by free and immobilised β‐glucosidase, including benzenic compounds, terpenic compounds, hydroxy esters, C₁₃‐norisoprenoids and alcohols.     

Production,Characterization, and Stability of Orange or Eucalyptus Essential Oil/β‐Cyclodextrin Inclusion Complex

The aim of this study was to produce and characterize inclusion complexes (IC) between β‐cyclodextrin (β‐CD) and orange essential oil (OEO) or eucalyptus essential oil (EEO), and to compare these with their pure compounds and physical mixtures. The samples were evaluated by chemical composition, morphology, thermal stability, and volatile compounds by static headspace‐gas chromatography (SH‐GC). Comparing the free essential oil and physical mixture with the inclusion complex, of both essential oils (OEO and EEO), it was observed differences occurred in the chemical composition, thermal stability, and morphology. These differences show that there was the formation of the inclusion complex and demonstrate the necessity of the precipitation method used to guarantee the interaction between β‐CD and essential oils. The slow loss of the volatile compounds from both essential oils, when complexed with β‐CD, showed a higher stability when compared with their physical mixtures and free essential oils. Therefore, the results showed that the chemical composition, molecular size, and structure of the essential oils influence the characteristics of the inclusion complexes. The application of the β‐CD in the formation of inclusion complexes with essential oils can expand the potential applications in foods.     

Characterization of volatile compounds in Fen‐Daqu – a traditional Chinese liquor fermentation starter

Fen‐Daqu is a saccharifying agent and fermentation starter for the production of Chinese liquor Fen (alcoholic spirit) and Fen traditional vinegar. The volatile compounds produced at seven incubation steps were analysed by HS‐SPME‐GC‐MS. A total of 83 major volatile compounds were identified, including 23 esters, 8 acids, 24 alcohols, 18 ketones and aldehydes, 6 pyrazines and 4 acetals. Data obtained by HS‐SPME‐GC‐MS were subjected to principal component analysis. The trajectory plots of volatile compounds in Fen‐Daqu samples obtained during successive steps of incubation were revealed. The major compounds that contributed to discrimination were hexanal, (E)‐2‐octenal, (Z)‐2‐octen‐1‐ol, nonanoic acid, 1‐octanol, 2‐decen‐1‐ol, hexyl acetate, (E)‐2‐octen‐1‐ol, acetic acid, ethyl acetate, phenylethyl alcohol, ethyl alcohol, octanoic acid, 1‐octanol, 3‐methyl‐2‐buten‐1‐ol and pyrazines. Copyright © 2012 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.     

Sensory and Chemical Analysis of ‘Shackleton's’ Mackinlay Scotch Whisky

Three cases of Mackinlay's Rare Highland Malt whisky were excavated from the ice under Sir Ernest Shackleton's 1907 expedition base camp hut at Cape Royds in Antarctica in January 2010. The majority of the bottles were in a pristine state of preservation and three were returned to Scotland in January 2011 for the first sensory and organoleptic analysis of a Scotch malt whisky distilled in the late 1890s. Sensory analysis and the higher alcohol and maturation congener profiles describe a lightly peated malt whisky matured in American white oak sherry or wine casks. Analysis of process related compounds together with combined gas chromatography (GC) mass spectrometry and GC‐olfactometry analysis of fermentation related congeners show a distinctly ‘modern’ style of malt whisky. While Scotch malt whisky at the end of the 19th century was generally regarded as heavily peated and harsh in character, Charles Mackinlay & Co. Distillers were producing a malt whisky with an altogether more subtle character at their Glen Mhor distillery near Inverness. The sensory and chemical analysis of this unique whisky artefact significantly changes our understanding of the quality and character of Scotch malt whisky produced by our distilling forefathers.     

Chemical Constituents of Gold‐red Apple and Their α‐Glucosidase Inhibitory Activities

Ten compounds were isolated and purified from the peels of gold‐red apple (Malus domestica) for the 1st time. The identified compounds are 3β, 20β‐dihydroxyursan‐28‐oic acid (1), 2α‐hydroxyoleanolic acid (2), euscaphic acid (3), 3‐O‐p‐coumaroyl tormentic acid (4), ursolic acid (5), 2α‐hydroxyursolic acid (6), oleanolic acid (7), betulinic acid (8), linolic acid (9), and α‐linolenic acid (10). Their structures were determined by interpreting their nuclear magnetic resonance and mass spectrometry (MS) spectra, and by comparison with literature data. Compound 1 is new, and compound 2 is herein reported for the 1st time for the genus Malus. α‐Glucosidase inhibition assay revealed 6 of the triterpenoid isolates as remarkable α‐glucosidase inhibitors, with betulinic acid showing the strongest inhibition (IC₅₀ = 15.19 μM). Ultra‐performance liquid chromatography‐electrospray ionization MS analysis of the fruit peels, pomace, flesh, and juice revealed that the peels and pomace contained high levels of triterpenes, suggesting that wastes from the fruit juice industry could serve as rich sources of bioactive triterpenes.     

Physicochemical and microbiological description of Caxiri – a cassava and corn alcoholic beverage

Caxiri is a fermented alcoholic beverage made from cassava, corn and sweet potatoes by indigenous people in Brazil. Saccharomyces cerevisiae Rhodotorula mucilaginosa, Lactobacillus fermentum, Bacillus subtilis and L. helveticus were the main microbial species detected. Maltose was the main carbohydrate found (19.12 g L^?1), and lactic acid (15.09 g L^?1) and ethanol (92.16 g L^?1) were also found in high concentrations. Gas chromatography‐flame ionisation detector was used to identify thirteen volatile compounds. Among these volatiles, the higher concentrations were decanoic acid (123.04 μg L^?1) for the acids, diethyl malate (88.32 μg L^?1) for the esters, furfural (109.31 μg L^?1) for the aldehydes, 2‐phenylethanol (1022.76 μg L^?1) for the alcohols and 1,1‐diethoxyethane (226.24 μg L^?1) for the others. This study contributes to increasing knowledge of the microbiota present in the alcoholic fermentation produced from cassava, corn and sweet potatoes.     

Freshness characterisation of whiting (Merlangius merlangus) using an SPME/GC/MS method and a statistical multivariate approach

BACKGROUND: The freshness of whiting was studied at five stages of ice storage by comparing the analysis of volatile compounds obtained through solid phase microextraction/gas chromatography/mass spectrometry (SPME/GC/MS) with two sensory methods. RESULTS: Of the volatile compounds identified, 38 were analysed using a statistical multivariate approach and classified according to their role in the estimation of freshness during storage as markers of freshness or spoilage. Regarding the evolution of the presence or absence of individual compounds, three categories were defined. For example, the volatile compounds propanal, hexanal, 1‐penten‐3‐ol, pentanal, 2,3‐pentanedione, 1‐penten‐3‐one, heptanal, (E)‐2‐pentenal, 2,3‐octanedione, (Z)‐2‐penten‐1‐ol, 1‐pentanol, butanal, octanal, 3,5,5‐trimethyl‐2‐hexene, 1‐hexanol and 4,4‐dimethyl‐1,3‐dioxane appeared highly relevant, because they are found throughout storage and can be divided into several categories that are directly related to the quality of fish. CONCLUSION: SPME/GC/MS combined with a statistical multivariate approach may be a useful method to identify volatile compounds and characterise fish freshness during storage. Copyright © 2010 Society of Chemical Industry     

Characterization of Volatile and Semi‐Volatile Compounds in Chinese Rice Wines by Headspace Solid Phase Microextraction Followed by Gas Chromatography‐Mass Spectrometry

The volatile and semi‐volatile compounds of Chinese rice wines were extracted by headspace solid phase microextraction (HS‐SPME) and analyzed by gas chromatography‐mass spectrum (GC‐MS). The original Chinese rice wine samples were diluted with deionized water to a final concentration of 6% (v/v) ethanol and then extracted by HS‐SPME. The samples were pre‐equilibrated at 50°C for 15 min and extracted with stirring at the same temperature for 45 min prior to injection into a GC‐MS. A total of 97 volatile and semi‐volatile compounds were identified from ten Chinese typical rice wine samples, including 13 alcohols, 8 acids, 28 esters, 4 aldehydes and ketones, 17 aromatic compounds, 3 lactones, 6 phenols, 3 sulphides, 9 furans and 6 nitrogen‐containing compounds, of which, 39 compounds were firstly reported in Chinese rice wine. By stepwise linear discrimination analysis, the ten Chinese rice wine samples could be classified into three groups according to the production area, and in particular, the production technologies.     

Behaviour of Volatile Compounds During Traditional Alembic Distillation of Fermented Muscat Blanc and Muškat Ruža Porečki Grape Marcs

To investigate the behaviour of volatile compounds during a traditional alembic distillation, large numbers of important volatile compounds were identified and quantified by GC/MS and GC/FID analysis in different fractions of grape marc distillates made from two Muscat varieties. Generally, concentrations of terpenes, C₁₃‐norisoprenoids, acids and particular waxy esters and aldehydes were found to increase, while concentrations of higher alcohols and the majority of fruity and flowery esters were found to decrease during distillation. Because of the abundance in odoriferous monoterpenes, utilization of the tail fraction as a raw material for re‐distillation was considered appropriate.     

Emulsifying properties and structural characteristics of β‐conglycinin and dextran conjugates synthesised in a pressurised liquid system

The purpose of this study was to characterise the Maillard reaction in a pressurised liquid system containing β‐conglycinin and dextran. The rate of browning and the free amino content in this liquid system, with an initial pH of 7.2, were measured after reaction under atmospheric pressure and at 10 MPa. The secondary and tertiary structures of the conjugates were analysed by circular dichroism, showing that the increased pressure accelerated the reaction rate of the free amino groups and reduced the rate of browning. Significant structural changes occurred in the tertiary structure of the conjugates. Additionally, the emulsifying properties of the β‐conglycinin–dextran conjugates produced were studied. The emulsifying properties of the conjugates produced at 10 MPa were higher than those made at atmospheric pressure.