Agglomeration of ethyl esters in model spirit solutions and malt whiskies

Medium- and long-chain ethyl esters were found to have a limited solubility when model spirits and malt distillates were diluted to 230 ml ethanol per litre for sensory analysis. At concentrations above this critical level the concentration of esters in solution remained constant, with the excess esters forming agglomerates. The saturated nature of the solution reduced the volatility of other esters, with a proportion of these compounds being partitioned into the agglomerate. The distribution was dependent on the mole fraction of each ester and its activity coefficient. Dissolution of wood extractives caused a number of changes in the solubility parameters of organic compounds; activity coefficients were increased and both the concentration and activity at which agglomeration occurred were decreased. This resulted in lower solution concentrations with increased concentrations in agglomerates. The reductions in free solution concentration could result in lower headspace concentrations, and thus have a direct effect on the flavour of the matured spirit.     

Aroma encapsulation and aroma delivery by oil body suspensions derived from sunflower seeds (<Emphasis Type="Italic">Helianthus annus</Emphasis>)

Oil bodies are small discrete cell organelles that can be found within oilseeds. Oil bodies have been investigated previously as a potential technology platform for use within the food industry, offering stable, antioxidant-enriched lipid-delivery systems. In this study, the use of oil bodies as a flavour delivery agent is evaluated. Fresh aromatized oil bodies show comparable headspace flavour intensity to phospholipid-stabilized emulsions when in a static equilibrium state, and when evaluated by dynamic headspace dilution, aromatized oil bodies showed a significantly stronger potential to maintain their headspace volatile concentration, which may indicate that oil bodies would offer greater retronasal flavour delivery than current commercial systems.     

Role of Organic Acids in Maturation of Distilled Spirits in Oak Casks

Maturation of whiskies and brandies in oak casks proceeds by reducing the perception of less desirable aromas of new distillates. During maturation, extraction of wood components increases the solubility of distillate compounds which reduces their headspace concentration above the matured spirit. The origins of this interaction are changes in aggregation of ethanol due to increases in contents of organic acids. During wood maturation organic acid concentrations in spirits increase as a result of extraction from cask wood, oxidation of ethanol and evaporation of ethanol and water. The effect of such changes was simulated using a model whisky ester in aqueous solutions of ethanol with acetic acid, oak wood extracts and acid fractions from new and matured Scotch malt distillates.     

Volatiles derived from lipoxygenase-catalysed reactions in winged beans (Psophocarpus tetragonolobus)

Volatiles formed by the decomposition of hydroperoxides generated by lipoxygenase-catalysed oxidation of linoleic acid contribute a beany flavour to legumes. Eleven volatiles have been identified after treatment of linoleic acid by lipoxygenase extracted from winged bean seeds. Five of these volatiles; namely, hexanal, 2-heptanone, 2-pentyl furan, undecane and tridecane, have been detected in the headspace of a sample of winged bean flour after storage. Moisture levels below 10% appear to inhibit lipoxygenase activity, since headspace samples from raw and heat treated samples had very similar composition, and the peroxide value remained low after 10 months' storage at 37°C. Incubation of a lipoxygenase extract with linoleic acid gave rise to a larger concentration of volatiles at pH 9 than at pH 6·5 due to the increased lipoxygenase activity at the higher pH.     

Headspace concentrations of ethyl esters at different alcoholic strengths

Ester concentrations in the headspace influence the aroma character of alcoholic drinks. Activity coefficients for esters showed log-linear decreases as ethanol concentration was increased from 17% (v/v), with rates inversely related to ester acid chain length. At concentrations below 17% (v/v) the activity coefficient remained constant. This could be related to structural changes in ethanol/water mixtures. Below 17% (v/v), ethanol forms a monodispersed aqueous solution. Above 17% (v/v), ethanol molecules cluster to reduce hydrophobic hydration and esters partition into these ethanol-rich clusters, where the lower ester interfacial tension reduces the free energy of mixing and hence the activity coefficient. The increased solubility of the ester reduced the headspace concentration of the esters, and hence total ester content may not be a good indicator of their flavour impact. © 1998 SCI.     

A Study of the Physico-chemical Behavior of Diacetyl in Hydroalcoholic Solution With and Without Added Catechin and Wood Extract

The interactions of diacetyl and ethanol in model solutions were studied in order to improve understanding of the changes in flavor perception that occur during both alcoholic beverage processing and consumption. A gradual reduction was demonstrated in the activity and partition coefficients of diacetyl as the ethanol concentration in aqueous solutions increased. From a sensory point of view, this fact would be expected to cause an increase in the diacetyl sensory thresholds. The expected diacetyl sensory thresholds were calculated based on experimental determination of the diacetyl vapor pressure in ethanol-water solutions at different ethanol concentrations. These sensory thresholds were not measured but merely obtained by theoretical interpolations. No significant variations in the activity coefficients of diacetyl were observed in the presence of catechin. Conversely, the dissolution of wood extract at 40% ethanol caused a significant decrease in diacetyl vapor pressure. The addition of catechin and wood extract to 40% ethanol-water solution contributed to the interactions of ethanol and water measured by DSC analysis.     

Ethanol-Extraktion von Ultradünnschnitten aus Fichten- und Buchenholz

Ultrathin cross sections of spruce and beech wood were extracted with ethanol at room temperature, 120 °C and 180 °C. The post-staining with KMnO₄ and a densitometric evaluation of the electron micrographs showed that very small amounts of lignin are predominantly dissolved from the secondary walls of spruce tracheids. The elevation of the extraction temperature to 180 °C results in an additional removal of lignin from the compound middle lamella. A uniform removal of lignin from the total cell wall even at room temperature is indicated for beech fibres.     

Variation of the Flavour and Extractives of European Oak Wood from Two French Forests

Wood from 20 trees from each of two French forests was heat treated and then stored in a 63% ethanol solution. After 6 months the concentrations of lignin degradation products, oak lactones, ellagic and gallic acids in the solutions were measured. The solutions were also assessed for flavour. Analyses of variance and principal component analyses found significant differences between the two forests in both the chemical composition of the solutions and in flavour assessments. Additional trials confirmed that the duration of heating influenced both chemical and flavour characters, but indicated that the effects may vary, depending upon wood properties and origin of the wood.     

Effects of killing conditions of vanilla (Vanilla planifolia,Andrews) pods during the curing process on aroma composition of pod ethanol extract

The effects on the aroma compositions of ethanol extracts obtained by traditional and enzyme‐assisted methods from seven killing conditions used in vanilla pod curing were studied. Two procedures of vanilla pod killing consisted of either freezing pods at ?10 °C for 24 h or immersing pods in 80 °C water for 10 s each of three times with 30 s intervals resulted in the highest vanillin values in terms percentage of dry weight of the bean (2.84 and 2.96), 4‐hydroxybenzaldehyde (0.18 and 0.20), vanillyl alcohol (0.56 and 0.57) and vanillic acid (0.18 and 0.19 respectively) when traditional vanilla ethanol extraction was used. When this extract was aged for 3 months it showed improvement in flavour compounds. Enzyme‐assisted vanilla ethanol extraction showed a higher content of flavour compounds than traditional extract, for example vanillin 4.38% and 2.96% respectively. Only vanillic acid levels were improved after ageing of the enzyme‐assisted extracts.     

Influence of saliva on temporal volatile flavour release from red bell peppers determined by proton transfer reaction-mass spectrometry

The effect of saliva on temporal volatile flavour release from rehydrated red bell peppers was evaluated. The addition of 40% artificial saliva (w/w) was studied using a model mouth combined with proton transfer reaction-mass spectrometry. Saliva reduced the maximum headspace concentration during temporal release of 2-methylpropanal, 2/3-methylbutanal and hexanal by 42% on average. This was attributed to an effect of saliva on both the thermodynamic and kinetic component of flavour release, as saliva resulted in an average decrease of 25% for these compounds in equilibrium headspace analysis. A preliminary comparison of model mouth and in-nose analysis showed that the model mouth mimicked temporal release under mouth conditions quite well.     

Aroma formation in Dianhong black tea: Effects of baking

Baking is the last, and yet most essential, step in the formation of the final distinct flavour of most black tea products. In this study, the influence of baking on the volatile components of Dianhong black tea, which is one of the most popular black teas in China, was investigated. As a very fast, effective, and simple method for collecting volatiles, headspace solid-phase microextraction (HS-SPME) with a 65 µm PDMS/DVB fibre was used to extract the volatile compounds of Dianhong black tea, and the volatile components were further separated and identified by gas chromatography-mass spectrometry (GC-MS). The results showed that the peak areas of alcohols, aldehydes, esters, and ketones were increased, but that those of some alkanes, acids, and nitrogen compounds did not demonstrate an obvious increase after baking. The differences generated by baking process actually result in the distinct flavour of most black teas and can be used as a model for analysing the chemical composition of special flavours, and for quality improvement and process control.     

Volatile flavour retention in food technology and during consumption: Juice and custard examples

In this study two aspects of the influence of water on flavour retention were evaluated. The first part of the study was focused on the influence of dehydration and subsequent reconstitution of mandarin juices, which was examined by headspace Proton Transfer Reaction Mass Spectrometry. The different treatments were discriminated by their mass spectra with help of Principal Component Analysis. The second part of the study concerned intranasal volatile flavour retention during food consumption. Volatile flavour concentrations were measured at four intranasal locations in nine subjects during consumption of custard desserts. Differences between the locations indicated various degrees of retention of volatile flavour compounds by the watery mucous in the nasal tract.     

Headspace fingerprinting approach to identify the major pathway influencing volatile patterns of vinasse-cured duck processed by high pressure,as well as its impact on physicochemical and sensory attributes

As a decisive attribute, flavour could be influenced by HP treatments through multiple physical and chemical pathways within the high pressure (HP)-assisted meat curing process. This investigation aimed to identify the major pathway influencing volatile flavour patterns of two representative vinasse-cured duck (VCD) products with HP treatments (150–300 MPa/15 min), including wet and dry types, by employing headspace fingerprinting as an untargeted approach. Results suggested that HP treatments greatly lowered moisture contents and increased Warner-Bratzler shear force and thiobarbituric acid reactive substances of the cured samples. According to multivariate models, the volatile flavour patterns of the HP-processed VCD could be clearly separated from the unprocessed samples, but the VCD pressurised at different intensities represented similar volatile fingerprinting, which was validated by e-nose analysis. The discriminant analysis (OPLS-DA) model outlined vinasse-derived ethanol, acetic acid, 3-methyl-1-butanol, 2-methyl-1-butanol, phenethyl alcohol and 2-methyl-3-octanone as the major discriminant aromas across the unpressurised and pressurised samples.     

Headspace concentration of selected dry-cured aroma compounds in model systems as affected by curing agents

The effect of curing agents (sodium chloride, nitrate, nitrite, glucose, and ascorbic acid) on the headspace concentration of six volatile compounds (2-methyl-butanal, 3-methyl-butanal, 2-pentanone, hexanal, methional, and octanal) has been studied. These volatile compounds were selected based on their presence and contribution to the flavour of typical Spanish dry-cured meat products. The release of volatile compounds to the headspace has been studied by using solid-phase microextraction (SPME) and gas chromatography analysis. The main effect was produced by sodium chloride, because it produced a salting-out effect on all the volatile compounds studied. Furthermore, the presence of nitrite, nitrate, and ascorbic acid in the solution also produced an increase in the headspace concentration of the volatile compounds while glucose decreased the headspace concentration of octanal and hexanal. The changes in the relative proportions of volatile compounds due to the effect of curing agents should be taken into account as they may change the flavour perception of dry-cured meat products.     

Improvement of the lipid oxidative stability of soybean oil-inwater emulsion by addition of daraesoon (shoot of <Emphasis Type="Italic">Actinidia arguta</Emphasis>) and samnamul (shoot of <Emphasis Type="Italic">Aruncus dioicus</Emphasis>) extract

The effect of 75% ethanol extract of daraesoon and samnamul (200 mg/kg) on the lipid oxidation of soybean oil-in-water (4:6, w/w) emulsion containing iron (5 mg/kg) in dark conditions at 25°C was studied by determining headspace oxygen and hydroperoxide contents. Polyphenol, carotenoid, and chlorophyll contents were also evaluated using spectrophotometry. The headspace oxygen contents were higher and hydroperoxide contents were lower (p<0.05) in the emulsions with added daraesoon and samnamul extracts compared with the control emulsion without the extract. The antioxidant activity of the daraesoon and samnamul extracts in the lipid oxidation of the emulsions was comparable to that of dibutylhydroxytoluene at 200mg/kg. Polyphenols, carotenoids, and chlorophylls were degraded during oxidation of the emulsions, possibly due to a role of the antioxidants. The results suggest that contribution to the improved lipid oxidative stability of the emulsion with added samnamul and daraesoon would be due to polyphenols and pigments, respectively.     

Wood nails to fix softwoods: characterization of structural deformation and lignin modification

Softwoods can be nailed with high density solid wood like Santos Rosewood (Machaerium scleroxylon) or nails made of densified laminated beech wood composite by hammering or shooting, for example with air nail guns, without pre-drilling. Shooting with about 30 m/s causes friction between nail surface and softwood matrix, heating up the interface to temperatures high enough to soften lignin. Re-condensation of softened lignin causes wood welding which doubles pull out strength in comparison to wood nails fixed without wood welding. Changes in lignin UV-absorption within the single cell wall layer and deformation of main anatomical features of spruce wood tissue are characterized by scanning UV microspectrophotometry (UMSP) whereas structural deformations of spruce wood tissue are revealed by X-ray micro-computed tomography (µ-CT).     

Characterisation of odour-active compounds in aged rum

The volatiles of rum matured in oak casks were carefully isolated by solvent extraction followed by solvent-assisted flavour evaporation. Among the 116 volatile compounds identified by GC-MS, seven of them were found for the first time in rum. Application of the aroma extract dilution analysis (AEDA) on the volatile fraction revealed 18 odour-active areas in the flavour dilution factor range of 32-1024. On the basis of the quantitative data and odour thresholds in 35% ethanol (v/v), the odour activity values (OAV; ratio of concentration to odour threshold) were calculated. Nineteen aroma compounds showed OAVs >1, among which ethanol, (E)-β-damascenone, ethyl butanoate, ethyl hexanoate, vanillin, (Z)-oak lactone, ethyl 2-methylpropanoate, 1,1-diethoxyethane, ethyl 2-methylbutanoate, 3-methylbutyl acetate, ethyl octanoate, ethyl decanoate, 2-phenylethyl acetate, 2-phenylethanol, 2-methoxyphenol, 4-ethyl-2-methoxyphenol, 4-propyl-2-methoxyphenol, γ-nonalactone, and eugenol showed the highest values and should be considered as the most odour-active compounds.     

The Influence of Yeast Strains on the Volatile Flavour Compounds of Chinese Rice Wine

In order to assess the influence of yeast strains on volatile flavour profiles of Chinese rice wine, small‐scale Chinese rice wine brewing was carried out with eight yeast strains from three different typical Chinese rice wine brewing regions. The volatile flavour compounds were extracted by headspace solid phase microextraction (HS‐SPME) and analyzed by gas chromatography‐mass spectrometry (GC‐MS). The volatile flavour profiles of the different Chinese rice wines showed statistically significant differences depending on the yeast strains used. Yeast strains from the Shaoxing region showed a higher capacity to produce the esters 2‐phenylethanol and 3‐methylthiopropanol, while yeast strains from the Shanghai region stood out for their production of branched‐chain higher alcohols. Chinese rice wine fermented with a yeast strain from the Jiangsu region had the highest levels of organic acids. Using principal component analysis of the Chinese rice wine volatile flavour compounds, the eight yeast strains could be classified into three groups according to their origins. This is the first report about the volatile flavour characteristics of Chinese rice wine yeast. The data obtained in this work shows that the yeast strains contributed significantly to the flavour differences of the Chinese rice wines from the different regions.     

Isoflavone Aglucones and Volatile Organic Compounds in Soybeans; Effects of Soaking Treatments

The effect of three different soaking treatments (6 hr in 50°C water; 6 hr in 50°C 0.25% NaHCO₃ solution; or 30 min in boiling 0.25% NaHCO₃ solution) was studied on the production of the major isoflavone aglucones, daidzein and genistein, and headspace volatile organic compounds including aldehydes, alcohols and furans in soybeans. Both 50° treatments resulted in production of substantial amounts of isoflavone aglucones and headspace volatile organic compounds. The boiling NAHCO₃ treatment inhibited production of isoflavone aglucones and lowered total headspace volatile organic compounds.     

Compositions,flavour and antiradical properties of products from subcritical water treatment of raw Isada krill

Comparative analysis of subcritical water (SCW) treatment and ambient pressure boiling one of raw Isada krill was performed for the nutritive, flavour and antiradical properties of krill extracts and residues as well as the molecular mass and odour intensity of the extract. SCW treatment was performed for 10 min in a batch‐type vessel in the temperature range of 100–240 °C, using a 1:1 weight ratio of raw krill to water. Higher protein and lipid contents were obtained by SCW treatment relative to boiling. The lipid content of the SCW extracts increased with increasing treatment temperature. Protein was the main component in these extracts, and the highest protein content was achieved by SCW treatment at 200 °C. High‐molecular‐mass species decomposed under SCW treatment at high temperatures with consequent generation of smaller molecules. The antiradical activity of the SCW extract, determined by DPPH and ABTS assays, increased with increasing treatment temperature. The krill extracts and residues exhibited shrimp‐like flavour, and the most desirable flavour was obtained by SCW treatment at 140 °C or 160 °C for 10 min. The treatment would be applicable for the production of seasonings from Isada krill.