Behavior Of Volatile Compounds Research Articles

Behaviour of volatile compounds during batch multi-stage distillation of whisky: experimental and simulation data

This study characterised the behaviour of congeners during the multi-stage discontinuous distillation of whisky using a Stupfler-type still. It also investigated the influence of recycling the head and tail fractions on the composition of the unaged spirit and, for the compounds with known equilibrium data, to validate the capability of software tools to simulate their behaviour during distillation. To this end, profile curves of ethanol (% ABV) and 45 aroma compounds (mg/L) during distillation are reported with 27 compounds, compared to simulated data using ProSim® BatchColumn software. Further, the mass distribution of each compound between the fractions of discarded head, recycled head, heart, tail and residue are estimated. Assuming that this distribution was maintained during each distillation, it was shown that for the wash, a pseudo-steady state was achieved in less than five distillations, and the true recovery rate of each compound in the heart was assessed. This study clearly demonstrates that during distillation, the congeners behave according to the ethanol content of the boiling liquid in the column. It provides real information on the separation of volatile compounds with a batch still with a distillation column above the heater. Additionally, the data highlights the importance to the unaged spirit of recycling the head and tail fractions. These results provide useful information for distillers to choose the appropriate way of collecting the heart fraction.

Influence of still design and modelling of the behaviour of volatile terpenes in an artificial model gin

Behaviour of volatile compounds in gin distillation using a batch column laboratory still has been investigated altering distillation parameters such as reflux strategy, pressure, and still design (column configuration). The distillate was separated into four equal fractions and ten volatile terpenes were quantified. Experimental values were compared to calculated data using a dynamic model calculated with ProSim BatchColumn software using a non-random two-liquid model to describe the interaction between solvents and terpenes. In the simulation different terpenes were considered and clustered into three group profiles. The monoterpene group was found to be the most volatile resulting in the highest concentration in the first fraction and depleting towards the end. The oxygenated terpenes increased in concentration with depleting ethanol concentration in the still and were therefore the least volatile compounds whereas the two representatives of the sesquiterpenes were found to be semi volatile. Changes in the column configuration resulted in major differences in the total concentration of terpenes extracted. The change of reflux strategy resulted in a higher concentration of the more volatile fraction at the higher reflux ratio chosen. The model showed a moderate agreement with the experimental data and only the monoterpenes considered showed good agreement.

Encapsulation of essential oils in SiO2 microcapsules and release behaviour of volatile compounds

Natural substances derived from plants such as essential oils (EOs) are used in a variety of applications such as in the release of fragrances or active substances in cosmetics, in food industries to protect sensitive ingredients against oxidative processes and as antimicrobial agents. However, the labile and volatile nature of EOs reduces their activity during application or storage. Here, the microencapsulation of EOs in silica capsules was investigated as a mean to control the fast release of their volatile constituents. The preparation of silica capsules with oil cores was obtained by employing a sol-gel method to oil-in-water-in-oil (O/W/O) multiple emulsions. The volatile release from the SiO2 capsules was investigated by comprehensive two-dimensional gas chromatography with time of flight mass spectrometry detection (GC × GC–ToFMS). This research demonstrates that the SiO2 capsules have selectively encapsulated the different volatile species and the corresponding release profiles depend on the chemical properties of each component.

Behaviour of volatile compounds during the shelf life of yoghurt

The production of acetaldehyde, diacetyl and ethanol was evaluated in whole plain yoghurts manufactured with commercial starter cultures, yoghurt acquired in a local market, and milk fermented by a single culture of either Streptococcus thermophilus or Lactobacillus delbrueckii ssp. bulgaricus. The headspace technique was used for sample preparation, following identification and quantification by gas chromatography. During an 8‐h incubation period, mixed cultures were the most efficient in lowering the pH (from 6.30 to 4.8), followed by S. thermophilus (from 6.30 to 5.18) and L. bulgaricus (from 6.30 to 5.8). During the storage period, however, a single culture of L. bulgaricus decreased the pH more than S. thermophilus, but still less than the mixed commercial cultures. Plain yoghurts acquired in the market, those made with commercial starter cultures, and fermented milks obtained with single cultures showed, after 21 days of storage, concentrations of acetaldehyde from 11 to 35 mg/L, and of diacetyl from 0 to 0.85 mg/L. An increasing concentration of ethanol was observed during the storage period, and its production was observed even in the incubation stage of all products. It was also observed that the acetaldehyde concentration was inversely correlated to ethanol production in some products. The combination of headspace, identification and quantification techniques by gas chromatography in this work was efficient in the identification and quantification of the major aromatic compounds and ethanol content of yoghurt.

Interaction between pollutants produced in sewage sludge combustion and cement raw material

Nowadays the use of waste as secondary fuel in clinker kilns is an extensive practice, but the interaction between cement raw material (CRM) and the combustion gases of the fuels has not been extensively studied. Because of that, in this work the effect of the interaction of exhaust from the combustion of sewage sludge and CRM has been studied in a laboratory furnace. The experiments were performed at 300 °C, close to the temperature at the cyclones in a cement industry. The behavior of volatile compounds, polycyclic aromatic compounds (PAH) and polychloro dibenzo- p-dioxin and polychloro dibenzofurans (PCCD/F) were analysed in the presence or absence of CRM. The results obtained show that the presence of CRM at the outlet of the combustion gases is beneficial for the decrease of pollutant emissions.

Assessment of the Volatile Composition of Juices of Apricot, Peach, and Pear According to Two Pectolytic Treatments

The behavior of volatile compounds according to two enzymatic treatments applied during the manufacture of fruit juice is described. More than 80 compounds were detected of a wide range of chemical families (alcohols, aldehydes, ketones, terpenoids, esters, norisoprenoids, ...). Theaspirane and alpha-isophoron were tentatively identified for the first time in apricot and peach fruits. The enzymes used, for extraction or clarification of fruit juices, modified the polysaccharides separated by molecular weight and the content of soluble polysaccharides. This could indicate differences in the fruit juice matrix, which could be related to observed changes in the volatile profile. In apricot, the enzymes enhanced the juice in terpenes and norisoprenoids as varietal compounds. In peach and pear, the enzymes used did not favor the amount of lactones and decadienoate esters, the character impact compounds, respectively.

Effect of pH on the behaviour of volatile compounds in organic manures during dry-matter determination

Dry matter determination by drying at 105°C is one of the most widespread methods used in the characterization of manure. Loss of volatile compounds during dry-matter determination may lead to considerable errors in mass balances. Since the behaviour of most volatile compounds depends upon pH, these losses may vary from sample to sample. The loss of ammonia and volatile fatty acids from pig, cattle and poultry manure was studied as a function of pH. It was shown that above pH 8 all ammonia was volatilized and below pH 5 all volatile fatty acids evaporated. Total fixation of ammonia was achieved below pH 4. Above pH 10 all volatile fatty acids were fixed in the residue after drying. The three types of manure showed only slightly different patterns of losses of volatile compounds. The amount of acid or alkali needed to obtain the desired pH varied strongly between the various kinds of manure.