Dynamic Headspace Gas Chromatography-mass Research Articles

Biopesticide Trunk Injection Into Apple Trees: A Proof of Concept for the Systemic Movement of Mint and Cinnamon Essential Oils.

The use of conventional pesticides is debated because of their multiple potential adverse effects on non-target organisms, human health, pest resistance development and environmental contaminations. In this setting, this study focused on developing alternatives, such as trunk-injected essential oil (EO)-based biopesticides. We analysed the ecophysiology of apple trees (Malus domestica) following the injection of Cinnamomum cassia and Mentha spicata nanoemulsions in the tree’s vascular system. Targeted and untargeted volatile organic compounds (VOCs) analyses were performed on leaf-contained and leaf-emitted VOCs and analysed through dynamic headspace–gas chromatography–mass spectrometry (DHS-GC-MS) and thermal desorption unit (TDU)-GC-MS. Our results showed that carvone, as a major constituent of the M. spicata EO, was contained in the leaves (mean concentrations ranging from 3.39 to 19.7 ng gDW–1) and emitted at a constant rate of approximately 0.2 ng gDW–1 h–1. Trans-cinnamaldehyde, C. cassia’s major component, accumulated in the leaves (mean concentrations of 83.46 and 350.54 ng gDW–1) without being emitted. Furthermore, our results highlighted the increase in various VOCs following EO injection, both in terms of leaf-contained VOCs, such as methyl salicylate, and in terms of leaf-emitted VOCs, such as caryophyllene. Principal component analysis (PCA) highlighted differences in terms of VOC profiles. In addition, an analysis of similarity (ANOSIM) and permutational multivariate analysis of variance (PERMANOVA) revealed that the VOC profiles were significantly impacted by the treatment. Maximum yields of photosystem II (Fv/Fm) were within the range of 0.80–0.85, indicating that the trees remained healthy throughout the experiment. Our targeted analysis demonstrated the systemic translocation of EOs through the plant’s vascular system. The untargeted analysis, on the other hand, highlighted the potential systemic acquired resistance (SAR) induction by these EOs. Lastly, C. cassia and M. spicata EOs did not appear phytotoxic to the treated trees, as demonstrated through chlorophyll fluorescence measurements. Hence, this work can be seen as a proof of concept for the use of trunk-injected EOs given the systemic translocation, increased production and release of biogenic VOCs (BVOCs) and absence of phytotoxicity. Further works should focus on the ecological impact of such treatments in orchards, as well as apple quality and production yields.

Host recognition by Rhinocyllus conicus of floral scents from invasive and threatened thistles

One of the main obstacles of classical biological control is that biological control organisms cannot be recalled once they are released in nature. It is particularly true for the flowerhead weevil, Rhinocyllus conicus Frolich, which was released as a biological control organism for the invasive musk thistle, Carduus nutans L. (MT). While weevils successfully suppressed introduced populations of musk thistles and other invasive thistle species, non-target attacks have been reported on multiple native thistles including federally listed threatened and endangered (T&E) thistle species. To investigate the foraging behavior of female weevils on invasive and native thistles, we examined volatile organic compounds (VOCs) emitted from MT and a T&E plant species, Sacramento Mountains thistle, Cirsium vinaceum Wooton & Standley (SMT) in the Lincoln National Forest, New Mexico. We used a dynamic headspace volatile collection system and gas chromatography-mass spectrometry to compare volatile profiles between MT and SMT. Female weevils reacted to 7 electrophysiologically active chemical compounds in the blends based on gas chromatography-electroantennography. The behavioral response of female weevils was indifferent when VOCs from both thistles were offered in y-tube olfactometry experiments. Yet, they preferred VOCs collected from MT to purified air. The searching time of female weevils was longer to VOCs collected from SMT over controls. Investigating signals during the initial host recognition of released biological control organisms may open new opportunities to reduce non-target attacks on T&E plant species.

Determination of certain VOCs in paints and architectural coatings by dynamic headspace gas chromatography-mass spectrometry.

A quantitative method for the determination of the following VOCs: acetone, dichloromethane, dimethyl carbonate, methyl acetate, tertiary butyl acetate, chlorobenzotrifluoride (4-CBTF) and propylene carbonate in paints was developed in support of Environment and Climate Change Canada's Automotive Refinishing Product and Architectural Coatings VOC Concentration Limits regulations. These compounds are excluded from the VOC definition by Canadian Environmental Protection Act (CEPA) regulations, and their content do not contribute to the overall VOC content in products for regulatory purposes. The method is based on Dynamic Headspace GC-MS. It was determined that activated carbon is the best trapping medium for these compounds. The technique has been compared to a currently used direct injection technique, with comparable results. Contrary to the direct injection method which requires complex sample handling prior to injection in the gas chromatograph, the dynamic headspace method practically eliminates the need for sample handling allowing for much shorter sample turnover and reducing the possibility of sampling handling errors.

Analysis of the Soil Fumigant, Dimethyl Disulfide, in Swine Blood by Dynamic Headspace Gas Chromatography–Mass Spectroscopy

Plant parasites and soilborne pathogens directly reduce the overall yield of crops, vegetables, and fruits, negatively impacting the market demand for these products and their net profitability. While preplant soil fumigation helps maintain the consistent production quality of high-value cash crops, most soil fumigants are toxic to off-target species, including humans. Dimethyl disulfide (DMDS) has recently been introduced as a relatively low toxicity soil fumigant. Although DMDS exhibits low toxicity compared to other soil fumigants, it is volatile and exposure can cause eye, nasal, and upper respiratory tract irritation, skin irritation, nausea, dizziness, headache, and fatigue. While there is one analysis method available for DMDS from biological matrices, it has significant disadvantages. Hence, in this study, a dynamic headspace gas chromatography–mass spectroscopy (DHS-GC-MS) method was developed for the analysis of DMDS in swine whole blood. This method is highly sensitive and requires only three steps: 1) acid denaturation, 2) addition of internal standard, and 3) DHS-GC-MS analysis. The method produced a wide linear range from 0.1 – 200 µM with an excellent limit of detection of 30 nM. Intra- and interassay accuracy (100±14% and 100±11%, respectively) and precision (<5% and <6% relative standard deviation, respectively) were also excellent. The method worked well to quantify the DMDS levels in the blood of dimethyl trisulfide (DMTS)-treated swine (i.e., DMDS is a byproduct of DMTS treatment) with no interfering substances at or around the retention time of DMDS (i.e., 2.7 min). This simple, rapid, and extremely sensitive method can be used for the quantification of DMDS levels in blood to verify exposure to DMDS or to monitor levels of DMDS following DMTS treatment (e.g., for cyanide poisoning).

Analysis of potential cyanide antidote, dimethyl trisulfide, in whole blood by dynamic headspace gas chromatography–mass spectroscopy

Cyanide is a rapidly acting and highly toxic chemical. It inhibits cytochrome c oxidase in the mitochondrial electron transport chain, resulting in cellular hypoxia, cytotoxic anoxia and potentially death. In order to overcome challenges associated with current cyanide antidotes, dimethyl trisulfide (DMTS), which converts cyanide to less toxic thiocyanate in vivo, has gained much attention recently as a promising next-generation cyanide antidote. While there are three analysis methods available for DMTS, they each have significant disadvantages. Hence, in this study, a dynamic headspace (DHS) gas chromatography–mass spectroscopy method was developed for the analysis of DMTS from rabbit whole blood. The method is extremely simple, involving only acidification of a blood sample, addition of an internal standard (DMTS-d6) and DHS-GC–MS analysis. The method produced a limit of detection of 0.04 μM for DMTS with dynamic range from 0.2 to 50 μM. Inter- and intraassay accuracy (100 ± 15% and 100 ± 9%, respectively), and precision (<10% and <9% relative standard deviation, respectively) were good. The validated method performed well during pharmacokinetic analysis of DMTS from the blood of rats treated with DMTS, producing excellent pharmacokinetic parameters for the treatment of cyanide exposure. The method produced significant advantages over current methods for analysis of DMTS and should be considered as a “gold standard” method for further development of DMTS as a potential next-generation cyanide countermeasure.

Losing a Scent of One’s Self: Is There a Reduction in Floral Scent Emission in Self-Pollinating Phlox cuspidata versus Outcrossing Phlox drummondii?

Premise of research. Studies of the evolution of self-pollination have generally predicted reductions in pollinator-attractive morphological floral traits over time as a result of relaxed pollinator-mediated selection and/or positive selection associated with improved self-pollination. Nonmorphological traits, such as floral scent, may also become reduced in self-pollinating taxa due to relaxed pollinator-mediated selection. However, evidence of such reductions in floral scent of selfing versus outcrossing taxa is limited. We explored this possibility in the scent of the predominantly selfing taxa Phlox cuspidata and its close outcrossing relative Phlox drummondii.Methodology. Scent was collected and analyzed from four populations of each plant species using dynamic headspace extraction and gas chromatography-mass spectroscopy. Scent emission rates were compared between species and among populations nested within species via MANOVA.Pivotal results. Of the 37 scent variables examined, only three showed significant differences between species. However, all three were emitted in decreased quantities from selfing P. cuspidata.Conclusions. While our findings provide some support for reductions of scent emission in selfing versus outcrossing annual Phlox, the retention of substantial scent production by P. cuspidata suggests continued dependence on pollinators (for either outcrossing or facultative selfing). This is further supported by maintenance of a pollen-ovule ratio similar to outcrossing P. drummondii. The retention of significant terpenoid emission alternatively indicates potential defensive functions for floral scent, as these compounds are known to have antiherbivore and antipathogen properties. Future research should examine both possibilities.

Methyl halide production by cultures of marine thraustochytrids, Aurantiochytrium sp., Botryochytrium radiatum, and Schizochytrium sp.

The oceans are an important source of the methyl halides released into the atmosphere and impacting the stratospheric ozone layer. Marine bacteria such as Erythrobacter and Pseudomonas are known to be sources of methyl halides in marine environments, but the production of methyl halides by thraustochytrids, the other decomposers in the marine ecosystem, have not been studied. Here, we report the productions of three methyl halides, CH3Cl, CH3Br, and CH3I, in cultures of thraustochytrids. Thraustochytrids were incubated at 20 °C, 25 °C, and 30 °C, and the concentrations of methyl halides in the gas phase above these cultures were determined using dynamic headspace gas chromatography–mass spectrometry. Growth of thraustochytrids was monitored by measuring optical density at 600 nm during the culture period. Cell density was also measured for some samples of thraustochytrids by counting with a plankton-counting chamber during the culture period. Three of the four tested strains of marine thraustochytrids were found to produce methyl halides in culture: Botryochytrium radiatum produced CH3Cl and CH3I while Aurantiochytrium sp. and Schizochytrium sp. produced CH3Br. Increases of CH3Cl, CH3Br, and CH3I concentrations were observed during the exponential-growth phase in all cultures of the three thraustochytrids, except for the 30 °C culture of B. radiatum. The maximum concentration for CH3Cl production by a thraustochytrid (B. radiatum) was increased as the culture temperature increased from 20 °C to 30 °C; the maximum concentrations of CH3Cl in the cultures incubated at 20 °C, 25 °C, and 30 °C were about 6000, 9600 and 14,000 pmol L−1, respectively. However, the maximum concentrations for the CH3I production of thraustochytrid (B. radiatum) decreased when the temperature was increased from 20 °C to 30 °C. To the best of our knowledge, this is the first report of methyl halide production by heterotrophic thraustochytrids. Our results suggest that thraustochytrids may be a source of methyl halides in marine environments.

Emission analysis of recycled tire rubber modified asphalt in hot and warm mix conditions.

The hazardous emissions of crumb rubber (CR) modified asphalt during construction has been a concern for a long period. This study aims to identify the emission components in the CR modified asphalt in traditional hot mix asphalt (HMA) and with recently developed warm mix asphalt (WMA). The dynamic headspace gas chromatography-mass spectrometry (GCMS) was employed for identifying the emission of asphalt binders at 120°C, 140°C and 160°C. The coupling of gas chromatography and Fourier-transform infrared spectroscopy (GC-FTIR) was used to analyze the emission during the plant mixing for conventional HMA, CR-HMA and CR-WMA. The results showed the emission amount was highly dependent on mixing temperature. The warm mix technology can reduce the emission level significantly and should be encouraged in the asphalt mixture containing CR. Asphalt source and other extra additives in producing CR modified asphalt can also affect the emission significantly. Asphalt mixture containing CR can release toxic emissions such as xylene and toluene significantly higher compared to that without CR. In addition, it was found that the emission amount from the GCMS test for asphalt binder was lower than that in the field test for asphalt mix due to the thin asphalt film of asphalt mix.

Physicochemical Properties and Oxidative Storage Stability of Milled Roselle (Hibiscus sabdariffa L.) Seeds

Milled Roselle (Hibiscus sabdariffa L.) seeds of the UMKL cultivar were analyzed for proximate composition, water and oil absorption capacity, and the influence of storage conditions on storage stability. The storage stability was determined under four types of conditions: light/oxygen (air) (LO), light/nitrogen (LN), darkness/oxygen (air) (DO), and darkness/nitrogen (DN) while monitoring for seven consecutive months. During the storage period, the formation of volatiles was determined using dynamic headspace sampling and Gas Chromatography-Mass Spectrometry (GC-MS) analysis. In total, 85 volatiles were identified, mainly aldehydes, alcohols, ketones, furans, and acids indicating lipid oxidation. It is recommended that milled Roselle seeds should be flushed with nitrogen and stored in darkness. Under these conditions, the seeds can be stored for at least three months without changes in volatile profile. This is important to ensure the good quality of milled Roselle seeds for further commercialization.

Effect of temperature on the production rates of methyl halides in cultures of marine proteobacteria

Abstract Methyl halides released from the ocean serve as important carriers of halogen into the atmosphere. The transported halogens are released into the atmosphere through photolysis, and catalyze ozone depletion. Marine bacteria are known to be a source of methyl halides in marine environments, but the effects of environmental temperature on the production of methyl halides by bacteria have not been studied. Here, we examined the effect of temperature on methyl halide production in a culture of marine bacteria (HKF-1) belonging to Erythrobacter , which was incubated for several days at 15 °C, 20 °C, 25 °C, or 30 °C. We also analyzed the effect of temperature on the production of methyl halides in a culture of the marine γ -proteobacterium Pseudomonas stutzeri . The concentrations of methyl halides such as CH 3 Cl, CH 3 Br, and CH 3 I in the gas phase above cultured samples were determined using dynamic headspace gas chromatography–mass spectrometry. Bacterial growth was monitored by measuring the optical density at 600 nm. The production rate of CH 3 Cl by marine bacteria (HKF-1) was increased with increasing temperature from 15 °C to 30 °C, and the maximum production rate for CH 3 Cl was ~ 19 pmol (10 9 cells) − 1 d − 1 at 30 °C, which was about 26 times higher than that at 15 °C (~ 0.7 pmol (10 9 cells) − 1 d − 1 ). The production rates of CH 3 Cl by P. stutzeri were also increased with increasing temperature from 15 °C to 30 °C. The production rates for CH 3 Br by bacteria (HKF-1) were increased with increasing temperature from 15 °C to 30 °C, whereas changes in the production rates for CH 3 I by these two bacteria were relatively small during the temperature rise from 15 °C to 30 °C. Higher production rates of CH 3 Cl, CH 3 Br, and CH 3 I were observed during the exponential phase than during the stationary phase in the cultures of HKF-1. The ratio of production rates (CH 3 Cl:CH 3 Br:CH 3 I) was 1.0:0.12:0.015 in the cultures of HKF-1, and this ratio was almost constant between 15 °C and 25 °C. These results suggested that water temperature could affect the production of methyl halides derived from bacteria and would be a significant factor for estimating the emissions of methyl halides from marine environments.

Effect of Fermentation Temperature on the Volatile Composition of Kimchi.

This study was conducted to evaluate the effect of fermentation temperature on the volatile composition in Kimchi. Kimchi was fermented at 2 temperature conditions (4 and 20 °C). Volatile compounds of Kimchi samples were analyzed during the fermentation periods using the dynamic headspace gas chromatography-mass spectrometry method. The optimum ripening time for the Kimchi fermented at 4 °C was 35 d, and that of 20 °C was 2 d. The pH at the optimum ripening time was 4.97 and 4.41, and the titratable acidity was 0.59% and 0.76% for the Kimchi fermented at 4 and 20 °C, respectively. Forty different types of volatile compounds, including alcohol, aldehyde, ester, and sulfur compounds, were identified. The Kimchi fermented at 20 °C produced greater amounts of volatile compounds than that at 4 °C. The amounts of most volatiles increased as the fermentation time increased, but those of aldehydes decreased rapidly during both 4 and 20 °C fermentation. Organic acids, ester, and nitriles were detected only in Kimchi fermented at 20 °C. The amounts of dimethyl disulfide, methyl-2-propenyl disulfide, and di-2-propenyl disulfide produced from the Kimchi fermented at 20 °C were more than 2-times of those at 4 °C. Therefore, it is concluded that the strong pungent odor of Kimchi fermented at 20° C is probably due to the high amount of organic acids (low pH) and sulfur compounds (dimethyl disulfide, methyl-2-propenyl disulfide, and di-2-propenyl disulfide) between the 2 Kimchi.

Oxidative stability and microstructure of 5% fish‐oil‐enriched granola bars added natural antioxidants derived from brown alga Fucus vesiculosus

The aims of this study were to (i) investigate the ability of Icelandic brown algae Fucus vesiculosus extracts to inhibit lipid oxidation in granola bars fortified with fish oil‐in‐water emulsion; (ii) investigate whether addition of the seaweed extracts affected the physical microstructure of the oil droplets in granola bars. The oxidative stability of the bars at 20°C was evaluated over a period of 10 wk by measuring the development of peroxides and volatile compounds using dynamic headspace gas chromatography mass spectrometry (DHS GC‐MS). The physical microstructure was determined using microscopy. All extracts − except water extract in low concentration − reduced lipid oxidation during 10 wk of storage when added in a concentration of 0.5 or 1 g extract/100 g emulsion. Ethanol (EE) and acetone extracts (AE) (in the lowest concentration) were found to be most efficient as antioxidants in the bars. The antioxidant efficacy of these two extracts was among other related to an improved incorporation of the fish oil‐in‐water emulsions in the bars, high total phenolic content, high radical scavenging activity together with high interfacial affinity of phenolic compounds and probably regeneration of tocopherol.Practical applications: The work showed the application potential of F. vesiculosus extracts as a natural antioxidant in low‐moisture foods such as granola bars. These findings implied that the multi‐functional nature of these extracts provides not only oxidative stability of the food but also a physical stability.Granola bars enriched with 10% Sodium caseinate (Na‐Cas) fish oil‐in‐water emulsion where Fucus vesiculosus extracts where added as antioxidant to control lipid oxidation. Development of secondary oxidation product, 1‐penten‐3‐ol (ng/g granola bar) in the granola bars and confocal light scattering microscopic images of granola bar added 0.5 g acetone extract/100g emulsion (AE1) and the Control (Con) (without extract). The efficacy of acetone extracts to limit development of 1‐penten‐3‐ol in granola bars was found to be related to extract composition as well as the microstructure, as fish oil emulsions in the bars were more stable when this extract was added. Error bars indicate SD of the measurements (n = 3).

Validation Study of Analysis of 1-Phenyl-2-Propanone in Illicit Methamphetamine Samples by Dynamic Headspace Gas Chromatography Mass Spectrometry

A new method based on dynamic headspace sampling (DHS) coupled to GC/MS analysis was developed, optimized and validated for the analysis of 1-phenyl-2-propanone (P2P) in illicit methamphetamine (MAMP) samples. The DHS parameters were investigated to reach the sensitivity suitable for this kind of analysis. The method showed of a good specificity, linearity, accuracy, precision and robustness. The analysis of ten MAMP samples seized by the judicial authority was carried out. P2P was found in all the seizure, confirming that P2P is the starting compound of the synthesis of amphetamines.

Development of a dynamic headspace gas chromatography–mass spectrometry method for on-site analysis of sulfur mustard degradation products in sediments

Sampling teams performing work at sea in areas where chemical munitions may have been dumped require rapid and reliable analytical methods for verifying sulfur mustard leakage from suspected objects. Here we present such an on-site analysis method based on dynamic headspace GC–MS for analysis of five cyclic sulfur mustard degradation products that have previously been detected in sediments from chemical weapon dumping sites: 1,4-oxathiane, 1,3-dithiolane, 1,4-dithiane, 1,4,5-oxadithiephane, and 1,2,5-trithiephane. An experimental design involving authentic Baltic Sea sediments spiked with the target analytes was used to develop an optimized protocol for sample preparation, headspace extraction and analysis that afforded recoveries of up to 60–90%. The optimized method needs no organic solvents, uses only two grams of sediment on a dry weight basis and involves a unique sample presentation whereby sediment is spread uniformly as a thin layer inside the walls of a glass headspace vial. The method showed good linearity for analyte concentrations of 5–200ng/g dw, good repeatability, and acceptable carry-over. The method's limits of detection for spiked sediment samples ranged from 2.5 to 11μg/kg dw, with matrix interference being the main limiting factor. The instrumental detection limits were one to two orders of magnitude lower. Full-scan GC–MS analysis enabled the use of automated mass spectral deconvolution for rapid identification of target analytes. Using this approach, analytes could be identified in spiked sediment samples at concentrations down to 13–65μg/kg dw. On-site validation experiments conducted aboard the research vessel R/V Oceania demonstrated the method's practical applicability, enabling the successful identification of four cyclic sulfur mustard degradation products at concentrations of 15–308μg/kg in sediments immediately after being collected near a wreck at the Bornholm Deep dumpsite in the Baltic Sea.

Decomposition of brominated organic halogens by cultures of marine proteobacteria: Phaeobacter, Roseobacter, and Rhodobacter

Brominated organic halogens such as bromoform (CHBr3) and dibromomethane (CH2Br2) play important roles as carriers of bromine from the ocean to the atmosphere. The bromine carried by these brominated methanes is released into the atmosphere, where it catalyzes ozone depletion. Previously, however, no microbial organisms capable of CHBr3 decomposition have been found in marine environments. In this study, we investigated bacteria to assess their capacity to decompose CHBr3 in temperate oceans. Bacteria were incubated with 13CHBr3 at 25°C and the concentrations of trace gases in the gas phase above the cultured samples were determined using dynamic headspace gas chromatography–mass spectrometry. Bacterial growth was monitored by measuring the optical density at 600 nm. 13CHBr3 was decomposed for several days by cultures of three different bacteria, Phaeobacter gallaeciensis, Roseobacter denitrificans, and Rhodobacter vinaykumarii, suggesting temperate marine bacteria can decompose CHBr3. The maximum 13CHBr3 decomposition rate was observed in the culture of P. gallaeciensis. The half-lives for 13CHBr3 decomposition by P. gallaeciensis, R. denitrificans, and R. vinaykumarii were 0.4 (0.3–0.5), 2.7 (2.5–2.9), and 2.0 (1.9–2.0) days, respectively. 13CH2Br2 and 13CHBr2Cl production were observed in the cultures, suggesting that 13CHBr3 was transformed into these compounds, and the production ratio of 13CH2Br2 was approximately 30% of the amount of 13CHBr3 spiked into the bacterial cultures. In contrast to CHBr3, CH2Br2 was not decomposed by the P. gallaeciensis, R. denitrificans, and R. vinaykumarii cultures. These results suggest that aquatic bacteria could act as a new sink for CHBr3 through decomposition in marine environments.

A comparative study on aromatic profiles of strawberry vinegars obtained using different conditions in the production process

Impact odorants in strawberry vinegars produced in different containers (glass, oak and cherry barrels) were determined by gas chromatography–olfactometry using modified frequency (MF) technique, and dynamic headspace gas chromatography–mass spectrometry. Aromatic profile of vinegar from strawberry cooked must was also studied. All strawberry vinegars retained certain impact odorants from strawberries: 3-nonen-2-one, (E,E)-2,4-decadienal, guaiacol, nerolidol, pantolactone+furaneol, eugenol, γ-dodecalactone and phenylacetic acid. Isovaleric acid, pantolactone+furaneol, p-vinylguaiacol, phenylacetic acid and vanillin were the most important aroma-active compounds in all vinegars. The strawberry cooked must vinegar accounted for the highest number of impact odorants. Wood barrels provided more aroma complexity than glass containers. Impact odorants with grassy characteristics were predominant in vinegar from glass containers, and those with sweet and fruity characteristics in vinegars from wood barrels. Principal component analysis indicated that the production process led to differences in the impact odorants.

Impact of starter cultures and fermentation techniques on the volatile aroma and sensory profile of chocolate

The sensory quality of chocolate is widely determined by the qualitative and quantitative composition of volatile compounds resulting from microbial metabolism during fermentation, and Maillard reactions taking place during drying, roasting and conching. The influence of applying mixed starter cultures on the formation of flavour precursors, composition of volatile aroma compounds and sensory profile was investigated in cocoa inoculated with cultures encompassing a highly aromatic strain of Pichia kluyveri or a pectinolytic strain of Kluyveromyces marxianus, and compared to commercially fermented heap and tray cocoa. Although only minor differences in the concentration of free amino acids and reducing sugars was measured, identification and quantification by dynamic headspace gas chromatography–mass spectrometry (HS/GC–MS) revealed pronounced differences in the composition of volatiles in roasted cocoa liquors and finished chocolates. 19 of the 56 volatile compounds identified in the chocolates were found in significantly higher amounts in the tray fermented sample, whilst significantly higher amounts of 2-methoxyphenol was measured in the two inoculated chocolates. The P. kluyveri inoculated chocolate was characterized by a significantly higher concentration of phenylacetaldehyde and the K. marxianus inoculated chocolate by significantly higher amounts of benzyl alcohol, phenethyl alcohol, benzyl acetate and phenethyl acetate compared to a spontaneously fermented control. Sensory profiling described the heap and tray fermented chocolates as sweet with cocoa and caramel flavours, whilst the inoculated chocolates were characterized as fruity, acid and bitter with berry, yoghurt and balsamic flavours. The choice of fermentation technique had the greatest overall impact on the volatile aroma and sensory profile, but whilst the application of starter cultures did affect the volatile aroma profile, differences were too small to significantly change consumer perception of the chocolates as compared to a spontaneously fermented control.

Volatile component profiles of conventional and lactose-hydrolyzed UHT milk—a dynamic headspace gas chromatography-mass spectrometry study

Lactose-hydrolyzed milk gains still increasing market share, and understanding the chemical characteristics of lactose-hydrolyzed milk products is important for the dairy industry. The aim of the present study was to identify and compare volatile compounds of commercial lactose-hydrolyzed and conventional ultra-high temperature (UHT) milk. For this purpose, the volatile compounds of lactose-hydrolyzed (<1% lactose), conventional (100% lactose), and filtered (60% lactose) UHT-treated milk were extracted using dynamic headspace sampling and analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 24 volatile compounds were identified including ketones, aldehydes, and sulfides. Overall, principal component analysis (PCA) showed grouping of the different milk types, with loadings indicating a higher concentration of ketones in conventional versus lactose-hydrolyzed UHT milk, but PCA also indicated a marked batch-to-batch variation. Elucidation of individual volatile compounds detected also revealed that the content of ketones in general was higher in conventional UHT milk than in lactose-hydrolyzed milk; however, no significant differences in the volatile compound profiles could be identified between the various milk types as a result of the batch-to-batch variation. The present study highlights a useful analytical method based on dynamic headspace sampling and GC-MS to profile volatiles important for the flavor characteristics of lactose-hydrolyzed and conventional UHT milk. In addition, the present study reveals that a considerable batch-to-batch variation exists in industrially produced batches of lactose-hydrolyzed UHT milk, which must be considered an important challenge for the dairy industry.

Transfer of terpenes from essential oils into cow milk

The objective of this study was to investigate the transfer of volatile terpenes from caraway seed and oregano plant essential oils into cow’s milk through respiratory and gastrointestinal exposure. Essential oils have potential applications as feed additives because of their antimicrobial properties, but very little work exists on the transfer of their volatile compounds into milk. Lactating Danish Holstein cows with duodenum cannula were used. Gastrointestinal exposure was facilitated by infusing the essential oils, mixed with deodorized sesame oil, into the duodenum cannula. Two levels were tested for each essential oil. Respiratory exposure was facilitated by placing the animal in a chamber together with a sponge soaked in the essential oils. All exposures were spread over 9h. Milk samples were collected immediately before and after exposure, as well as the next morning. Twelve monoterpenes and 2 sesquiterpenes were analyzed in essential oils and in milk samples using dynamic headspace sampling and gas chromatography-mass spectrometry. In the essential oils, almost all of the terpenes were detected in both essential oils at various levels. For caraway, the monoterpenes limonene, carvone, and carvacrol were most abundant; in oregano, the monoterpenes carvacrol and ρ-cymene were most abundant. For almost all treatments, an immediate effect was detected in milk, whereas little or no effect was detected in milk the following day. This suggests that the transfer into milk of these volatile terpenes is fast, and that the milk will not be influenced when treatment is discontinued. Principal component analysis was used to elucidate the effect of the treatments on the terpene profile of the milk. Terpene content for treatment milk samples was characterized by the same terpenes found in the treatment essential oil used for that animal, regardless of pathway of exposure. The terpenes appear to be transferred unaltered into the milk, regardless of the pathway of exposure. Volatile terpenes in essential oils, which could influence milk flavor, are transferred into milk via both gastrointestinal and respiratory exposure.

Oxidative Stability of Polyunsaturated Edible Oils Mixed With Microcrystalline Cellulose.

The oxidative stability of mixtures of edible oils containing polyunsaturated fatty acids (PUFA) and microcrystalline cellulose (MCC) was investigated. The mixtures studied consisted of oils of either camelina (CAM), cod liver (CLO), or salmon (SO) mixed with either colloidal or powdered MCC. A 50:50 (w/w) ratio of oil:MCC resulted in an applicable mixture containing high levels of PUFA edible oil and dietary fiber. The oxidative stability of the formulated mixtures and the pure oils was investigated over a period of 28 days. The peroxide value (PV) was assessed as a parameter for primary oxidation products and dynamic headspace gas chromatography mass spectrometry (GC/MS) was used to analyze secondary volatile organic compounds (VOC). CAM and the respective mixtures were oxidatively stable at both 4 and 22 °C during the storage period. The marine oils and the respective mixtures were stable at 4 °C. At 22 °C, an increase in hydroperoxides was found, but no increase in VOC was detected during the time-frame investigated. At 42 °C, prominent increases in PV and VOC were found for all oils and mixtures. Hexanal, a common marker for the degradation of n-6 fatty acids, propanal and 2,4-heptadienal (E,E), common indicators for the degradation of n-3 fatty acids, were among the volatiles detected in the headspace of oils and mixtures. This study showed that a mixture containing a 50:50 ratio of oil:MCC can be obtained by a low-tech procedure that does not induce oxidation when stored at low temperatures during a period of 1 month.