A novel gas chromatographic stationary phase in a wall-coated open tubular column embodiment was employed successfully for carbon number grouping of up to C10. This unique cross-linked and bonded stationary phase, based on alicyclic polysiloxane chemistry, displays a polarity index even lower than the widely used 100% dimethylpolysiloxane phase. Critical pairs of probe compounds employed in a standard capillary column test mixture, such as 2,4-dimethylphenol/undecane and 2,6-dimethylaniline/naphthalene that are co-eluted on a 100% dimethylpolysiloxane phase, are well separated on this unique stationary phase with an R value greater than 1.5. The stationary phase has a respectable maximum operating temperature of 280 oC and is demonstrated to have a high degree of inertness. The gas chromatographic column is suitable for use in determining heat energy value in fossil fuels like natural gas which is highly critical to industry for energy measurement, natural gas trading, and regulatory compliance. The column technology is suitable for other challenging industrial applications involving ultra-volatile and volatile molecules such as sulfur-containing compounds and oxygenated compounds.

A straightforward and practical 15-min gas chromatographic method utilizing flame ionization detection has been developed to measure hydrogen cyanide in various matrices. This new approach features a catalyzed two-stage post-column reaction that significantly enhances the detection and quantification of hydrogen cyanide. Selecting the right separation column is crucial for accurate analysis. Initial tests with porous layer open tubular columns resulted in significant peak tailing, rendering them unsuitable for trace-level analysis. Modified polyethylene glycol stationary phases also exhibited strong peak tailing in addition to producing artifact peaks. In contrast, a polydimethylsiloxane-based column with a very low phase ratio (β = 10) demonstrated excellent analytical performance, including peak symmetry and inertness. The analytical approach achieved a minimum detection limit of 50 parts per billion (ppb, v/v) without preconcentration and a linear range from 0.05 to 200 parts per million (ppm, v/v). At a concentration level of 20 ppm (v/v), the RSD at the 95% confidence level was less than 1% (n = 10), and at a concentration level of 1 ppm (v/v), the RSD at the 95% confidence level was less than 3% (n = 10) under the established conditions. The method's effectiveness has been validated through real-life applications, including analyzing hydrogen cyanide in fruit seeds and the headspace of untreated water samples.

Gas chromatography (GC), along with other chromatographic techniques, is vitally important in forensic science to separate substances of analytical interest. This article explores some of the theory of GC and leads the reader through discussion of separation columns, sample introduction, and detection. A discussion of choice of operating parameters such as pneumatic conditions, and temperature settings is also provided, and some advanced GC approaches are briefly introduced.

Foodborne pathogens and spoilage microorganisms are a source of concern for public health and the food industry. Considering the problem of antimicrobial resistance in microbes, controlling these microorganisms using synthetic antimicrobials is challenging, thus, essential oils are a potential natural alternative. Previous studies have predominantly focussed on the antimicrobial activity of essential oils in the liquid phase. However, in this work we report on the in vitro antimicrobial activity of the liquid and vapour phases of essential oils from native Australian plants Tasmanian mountain pepper (Tasmannia lanceolata), lemon myrtle (Backhousia citriodora), as well as the common herb thyme (Thymus vulgaris) against 11 common food spoilage and pathogenic bacteria and fungi. Initial screening was conducted using the disc diffusion assay. The minimum inhibitory concentration (MIC) of the oils was determined using the broth microdilution assay. The vapour phase antimicrobial activity of the oils was assessed using an inverted petri plate assay and the vapour phase MIC (V-MIC) was quantified using a vapour diffusion assay. GC-MS was adopted to elucidate the compositional profile of the oil in liquid phase. Two extraction methods, namely solid-phase microextraction (HS-SPME) and gas tight syringe headspace sampling (HS) coupled with GC-MS were used for profiling the composition of the volatiles. The findings of this study confirmed the antimicrobial activity of the oils in both liquid and vapour phases, with lemon myrtle and thyme generally showing stronger antimicrobial activity than Tasmanian mountain pepper. The activity in liquid phase was generally higher than the volatiles. However, lemon myrtle and Tasmanian mountain pepper berry volatiles were more effective against Aspergillus niger and Saccharomyces cerevisiae, respectively, relative to the liquid phase highlighting their potential as vapour phase antifungals. In the liquid and gas phases, the major compounds in lemon myrtle were Z-citral (neral) and E-citral (geranial). Polygodial and thymol were the major compounds in Tasmanian mountain pepper and thyme in the liquid phase, respectively. However, the main compounds in their volatiles were p-cymene and γ-terpinene. In conclusion, our research indicates the essential oils' potent vapour phase activity, highlighting their potential application in gaseous diffusion-dependent food applications such as active antimicrobial food packaging.

Many essential oils have garnered attention as promising antimicrobials; however, their inherent volatility and susceptibility to degradation limit their effective utilisation. Encapsulation can address these limitations by entrapping the essential oils within protective matrices. In the current study, native Australian essential oils, Tasmanian mountain pepper (Tasmannia lanceolata) and lemon myrtle (Backhousia citriodora) and non-native thyme (Thymus vulgaris) were encapsulated in lipid nanoparticles (LNs) using high-pressure homogenisation. The morphology, size, stability and release properties of the LNs was assessed using cryo-TEM, DLS, turbiscanning and dialysis, respectively. The encapsulation efficiency of the LNs was determined using ultrafiltration and GC-FID analysis. The liquid and vapour phase antimicrobial activity and mode of action were determined using microdilution, inverted petri plate assays, and TEM, respectively. Stable spherical LNs (<200 nm size) with encapsulation efficiencies <88% and polydispersity index <0.2 were formulated. LNs generally showed higher antimicrobial activity than unencapsulated oils except for vapour phase activity which varied amongst the oils. Time-dependent cell membrane damage was confirmed using TEM. Essential oils exhibited a bi-phasic release profile from LNs characterised by initial burst release, followed by sustained release. In summary, encapsulation stabilised, promoted sustained release and enhanced the antimicrobial efficacy of the essential oils.

Proline has recently been found to direct several sensory attributes in red wine, including viscosity, fruit flavour and sweetness. We sought to investigate whether a red wine, deemed ‘flavour deficient’ by a producer, from a warm inland region could be improved by blending with a high proline wine from the same region, compared to a high colour and flavour wine, linking consumer acceptance with sensory properties and chemical composition. Three dry red wines (two Cabernet-Sauvignon wines from a warm region and one Lagrein wine from a cooler region) were blended in a constrained mixture design. Several blends were uncovered with improved sensory properties and consumer liking scores. Increased liking scores were related to heightened perceived Viscosity (unrelated to physical viscosity), Sweetness and Berry flavours, connected to proline-rich wines with small proportions of Lagrein. PLS-R models relating blend chemical composition, sensory properties and consumer acceptance associated Astringency and Bitterness to polyphenolics and organic acids and lower liking scores. Vegetal and Leather aromas in blends also reduced consumer acceptance and were related to the concentration of the thiols 3SH, 3SHA, PMT, 2FMT and MeSH, as well as guaiacol and isobutyl methoxypyrazine. Multiple blends successfully improved consumer acceptance of the ‘flavour deficient’ wine, particularly those with an increased proportion of the proline-rich wine. Non-linear effects resulting from blending were also assessed, with most variables modelled best by linear averaging. This study demonstrates the practical application of a design of experiment approach using sensory properties, proline and polyphenolic concentrations to guide wine blending and improve wine flavour and acceptability.

Background and Aims. A wide range of Chardonnay styles exist on the market, from fruit-forward examples to wines displaying "empyreumatic" aromas such as flint, smoky, mineral, and struck-match. The thiols 2-furylmethanethiol and phenylmethanethiol have been linked to these aromas, and this study aimed to determine the contribution of these compounds to specific sensory properties in Chardonnay wines, as well as the consumer acceptance of wine displaying "empyreumatic" aromas. Methods and Results. Twenty-four Australian and New Zealand Chardonnay wines were selected for volatile analysis and quantitative sensory descriptive analysis. Consumer liking of a subset of six wines was also determined, and a further sensory study involving additions of the thiols to a base wine was conducted. Partial least squares regression showed that flint/struck-match/mineral aromas were related to 2-furylmethanethiol concentration with phenylmethanethiol less well associated. The odorant addition study confirmed that 2-furylmethanethiol directed flint/struck-match/mineral aromas and exerted strong suppression of other aromas while phenylmethanethiol played a lesser role. Consumer acceptance (n = 92) was overall lower for wines displaying high flint/struck-match/mineral aromas, although cluster analysis of the liking scores identified a sizeable consumer group (33%) who preferred wines with this attribute. Conclusions. The potent thiol 2-furylmethanethiol was indicated to be the primary contributor to flint/struck-match/mineral aromas in Chardonnay wines, with phenylmethanethiol playing a subordinate role. Significance of the Study. Increased concentration of 2-furylmethanethiol and the conferred "empyreumatic" odours should be carefully considered when producing wine styles to appeal to consumers.

An approach using pyrolysis with comprehensive two-dimensional gas chromatography with flame ionization detection is introduced for identifying common isolated plastic polymers. A quadrupole mass spectrometer is employed as a parallel detector to aid method development and improve polymer identification in complex matrices. Common plastic polymers including polyethylene , polypropylene , polystyrene , polyvinyl chloride , polyamide , poly(methyl methacrylate) , styrene-butadiene rubber , and polyethylene terephthalate are accurately identified within a total analysis time of 45 min. A strategy to enhance compatibility of high-resolution capillary gas chromatography using a 150-µm internal diameter column technology and a larger internal volume microfurnace–based pyrolyzer is discussed. This strategy resulted in minimizing the band broadening effect caused by the pyrolyzer’s internal volume and overcoming the slow pressure buildup when the sample is inserted into the furnace. Prolonged pressure buildup to reach a final pressure setting can cause a safety shutdown to the pneumatic control system. The developed approach is complementary to spectroscopic techniques by offering mass based, chemical composition analysis of plastics.

An approach employing static headspace-comprehensive two-dimensional gas chromatography with backflushing for rapid detection of Escherichia coli in milk is introduced. Presence of E. coli is indicated by detecting microbial volatile organic compounds emanating from contaminated samples. Headspace equilibration for 15 min followed by 5 min chromatographic analysis of enriched samples reduces time-to-response by approximately one whole day compared to conventional culture-based methodology and it is possible to detect single cell bacterial load in milk. It is shown that presence of ethanol, 1-propanol, acetonitrile, and acetaldehyde may be used as putative markers of E. coli contamination. Detecting pathogens and / or spoilage microbes in food products is critical for the food industry and the described approach has great potential to complement the conventional workflow for detecting microbial food contamination.

Background and Aims The effect of amino acids, and their interactions with volatiles and other non-volatiles, on in-mouth sensory properties of red wines is not known. This knowledge gap has been studied in a series of comprehensive sensory experiments. Methods and Results A solvent-assisted flavour evaporation extract of Shiraz wine volatiles, a de-aromatised polyphenolic extract and amino acids were added to model wine and wine systems. Using full factorial designs, samples were evaluated by sensory quantitative descriptive analysis. Volatiles enhanced Viscous mouthfeel (F = 20.0, P < 0.001), Sweetness (F = 26.5, P < 0.001) and Body (F = 81.4, P < 0.001), while the phenolic extract directed Astringency (F = 170.5, P < 0.001) as well as Bitterness (F = 7.3, P < 0.001) and suppressed Sweetness (F = 16.5, P < 0.001). An amino acid by volatile interaction (F = 4.2, P < 0.05) was found, and further experiments showed that L-proline enhanced Viscosity (F = 5.0, P < 0.05), Sweetness (F = 14.4, P < 0.001), Red fruit flavour (F = 7.8, P < 0.001) and suppressed Astringency (F = 6.1, P < 0.05) and Bitterness (F = 7.0, P < 0.01), while L-glutamic acid imparted an Umami taste (F = 5.0, P < 0.05) at wine-like concentration. Conclusions For the first time, these causal experiments showed that amino acids can influence the taste, mouthfeel and flavour of red wine. Significance of the Study This work provides insight into a new class of wine compounds of sensory significance that can be targeted by producers to directly influence wine flavour.

AbstractCoffee aroma is a complex mixture of volatile compounds. This study characterized the important aroma‐active compounds associated with consumer liking in formulated coffee‐flavored dairy beverages. Nine coffee‐flavored dairy beverages were formulated: low fat–low coffee; medium fat–low coffee; high fat–low coffee; low fat–medium coffee; medium fat–medium coffee; high fat–medium coffee; low fat–high coffee; medium fat–high coffee; and high fat–high coffee. Regular coffee consumers, (n = 231) used a nine‐point hedonic scale to rate acceptance of aroma. Volatile compounds were extracted by head space‐solid phase micro‐extraction (HS‐SPME) and analyzed by gas chromatography‐mass spectrometry‐olfactometry (GC‐MS‐O) using a modified frequency (MF) approach. Fifty‐two aroma‐active compounds were detected. Thirty‐one aroma‐active compounds were considered important compounds with MF‐value ≥ 50%. The total number of aroma‐active compounds and their intensity were affected because of fat and coffee concentration. Partial least squares regression (PLSR) was performed to determine the relationship between aroma‐active compounds and liking. PLSR analysis identified three groups of compounds regarding liking. Twenty‐five compounds were associated with positive liking, for example, 2‐(methylsulfanylmethyl) furan (coffee like). Sixteen compounds were negatively associated with liking, for example, 2‐methoxyphenol (bacon, medicine like). Eleven detected compounds had no association with liking, for example, butane‐2,3‐dione (butter, fruit like).Practical Application: The result of this study may be applied to formulate coffee‐flavored dairy beverages to maximize consumer acceptance and aroma‐liking. This study suggested too low coffee concentration is not desirable. Too much fat affects aroma release and/or alters the characteristic coffee flavor which negatively affects consumer acceptance.

Contamination of food by spoilage and pathogenic microorganisms is a major challenge to public health, food security and sustainability. As a response, there has been a growing interest in the exploration of alternative antimicrobial agents such as essential oils. Although essential oils can be potent antimicrobials, they are chemically and biologically labile and have strong aromas which limit their application as food antimicrobial additives. This has shifted essential oil research from direct food applications towards the use of encapsulated essential oils in active packaging. Various encapsulation methods are increasingly being explored as a way of stabilizing essential oils, masking their aromas and possibly improving their antimicrobial activity with a more sustained release of the antimicrobials. Encapsulated essential oils have mainly been investigated as direct preservatives but their merit in active packaging is comparatively less explored. The current review will critique some currently available encapsulation techniques and their effect on the antimicrobial efficacy, release profiles, stability and sensory properties of the essential oils. Furthermore, the application of encapsulated essential oils in biodegradable active packaging will be explored by focusing on the antimicrobial efficacy, release properties and physicochemical properties of the packaging.

A new approach is introduced for rapid and reliable bacteria detection in food. Namely, static headspace-comprehensive two-dimensional gas chromatography (HS-GC × GC) with backflushing. The introduced approach provides fast detection of Escherichia coli ( E. coli ) in enriched ultra-high-temperature processed (UHT) dairy milk. The presence of E. coli may be indicated by detecting microbial volatile organic compounds emanating from test solutions inoculated with E. coli . In the present investigation, HS-GC × GC analysis is preceded by conventional enrichment in nutrient broth and inoculated samples are clearly discernable from controls following as little as 15 h sample enrichment. Headspace equilibration for 28 min followed by an 8 min GC × GC analysis of enriched test solutions reduces time-to-response by approximately one full day compared to conventional culture-based methods. The presence of ethanol, 1-propanol, and acetaldehyde may be used as a putative marker of E. coli contamination in milk and the introduced approach is able to detect single-cell initial bacterial load. Faster, reliable detection of pathogens and/or spoilage microbes in food products is desirable for the food industry. The described approach has great potential to complement the conventional workflow and be utilised for rapid microbial screening of foodstuff.

Rice is consumed as a staple food by more than half of the world’s population. Due to a higher fibre and micronutrient content, brown rice is more nutritious than white rice, but the consumption of brown rice is significantly lower than that of white rice, primarily due to sensory attributes. Therefore, the present research aimed to identify the sensory attributes which drive liking of Australian-grown brown and white rice varieties. Participants (n = 139) tasted and scored (9-point hedonic scale) their liking (i.e., overall liking, aroma, colour and texture) of brown and white rice types of Jasmine (Kyeema), Low GI (Doongara), and Medium grain rice (Amaroo). In addition, participants scored aroma, colour, hardness, fluffiness, stickiness, and chewiness, on Just About Right Scales. A within-subjects crossover design with randomised order (William’s Latin Square design) was used with six repeated samples for liking and Just About Right scales. Penalty analyses were applied to determine the relative influence of perception of sensory attributes on consumer liking of the rice varieties. Across all varieties, white rice was liked more than brown rice due to the texture and colour, and Jasmine rice was preferred over Low GI and Medium Grain. Rice texture (hardness and chewiness) was the most important sensory attribute among all rice varieties and aroma was important for driving of liking between white rice varieties.

The fat content of a product has the potential to influence consumer liking via mouthfeel, taste, and aroma modification. This study aims to determine the effects of fat and coffee concentration on sensory attributes and consumer liking of iced-coffee beverages. Nine iced-coffee beverages were formulated: low fat-low coffee; medium fat-low coffee; high fat-low coffee; low fat-medium coffee; medium fat-medium coffee; high fat-medium coffee; low fat-high coffee; medium fat-high coffee; and high fat-high coffee. Fat content was adjusted using different concentrations of cream, and coffee using different concentrations of Nescafé Blend 43. Regular coffee consumers (n = 231) rated their overall liking using a 9-point hedonic scale and completed a ranked preference based on degree of liking of all samples. Consumers also rated liking for sensory attributes: appearance, aroma, sweetness, coffee intensity, mouthfeel, and aftertaste. There were significant relationships between 1/ fat and 2/ coffee and liking of iced-coffee beverages (p < 0.001). There were three clusters of consumers based on iced-coffee preferences. Response surface curve indicated that overall liking of iced-coffee beverages increased with the increase of fat and coffee concentration to a certain level, then continuing to increase the fat and coffee concentration decreases overall liking. The finding of this study provides valuable information on how fat and coffee concentrations can be adjusted to modify consumer acceptance of iced-coffee beverages. PRACTICAL APPLICATION: The results of this research could be applied to reformulate iced-coffee beverages, while ensuring consumer acceptance. In addition, this research provides evidence that sweetness, aftertaste, coffee-intensity, and mouthfeel are important sensory attributes associated with consumer liking of iced-coffee beverages.

Using UV spectroscopy as a selective detection approach in gas chromatography (GC) has been demonstrated here with a diode array detector (DAD). The benefits of using an UV detector in GC were realized through effective thermal management and inertness improvement. The approach deployed in this study was proven to be effective for either tandem or parallel detection and has the potential to be used in chromatographic separations that require stringent, narrow bandwidths, such as comprehensive two-dimensional gas chromatography (GCxGC).

A new automated micro liquid-liquid extraction technique was successfully developed. This novel syringe-based technique capitalizes on the advantages of vigorous fluid agitation and the shearing effect of two fluids with different properties to achieve high extraction efficiency. The technique is at least 20 times faster than mechanical shaking or sonication in achieving a similar recovery even with a hydrophilic probe molecule such as 1,4-dioxane in an aqueous medium. Excellent repeatability with a relative standard deviation as low as 0.56% over a five-day test, n = 2 per day, was demonstrated with 1,4-dioxane. Other model compounds in aqueous matrices evaluated, including phenolics and extraction solvents like chloroform and hexane, showed similar performance in repeatability. An added advantage of this technique involves performing multiple extractions. Its capabilities in conducting complicated extraction steps and minimizing the use of organic solvents as low as 200 µL to achieve a preconcentration effect were demonstrated. The technique is suitable for use with emulsion-forming samples without further sample manipulation by incorporating a demulsifier such as acetone during the extraction process. The technique was found to be efficient and environmentally friendly with low solvent waste. This technique is ideal for implementation in automated high throughput and cost-effective quality assurance laboratory environments.

Liquid-liquid extraction is one of the most widely used and simplest sample preparation techniques. However, consumption of large volumes of organic solvent and manual handling are two major drawbacks of this technique. A multifunction autosampler syringe is introduced which permits automated liquid-liquid extraction in an enclosed operating environment, with low consumption of organic solvents. The device described herein features a micromixer function in addition to common autosampler syringe features like accurate and precise aspirating and dispensing. To test the functionality of the micromixer syringe, manual extraction of caffeine from a tea infusion and semi-automated extraction of dichloroethane from water were carried out. Excellent recoveries of caffeine from a tea infusion (89% recovery with 1.3% RSD) and dichloroethane from water (107% recovery with 10% RSD) were obtained. Two automated workflows were tested using the micromixer syringe mounted in a laboratory autosampler. Standalone automated micro liquid-liquid extraction was performed for sample preparation of selected polychlorinated biphenyl (PCB) congeners prior to comprehensive two-dimensional gas chromatography – electron capture detection analysis. Extraction of PCBs using the described approach used substantially less solvent than a validated solid-phase extraction approach whilst delivering equivalent results for samples with high-level PCBs. Finally, fully automated extraction and GC-MS analysis of polynuclear aromatic hydrocarbons (PAHs) from water samples was performed. Mean recoveries of extraction for PCB and PAH analysis were > 70% using 4 min automated liquid-liquid extractions.