Browsing by Subject "SPME"

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  • Tuccillo, Fabio (Helsingin yliopisto, 2021)
    As the number of vegetarians and flexitarians is increasing, the demand for meat alternatives is following the same trend. Faba bean is a promising crop for environmental, health, and social reasons. From its seeds, several products can be produced, such as flour, protein concentrate, and protein isolate. These materials can be further processed for the development of texturized vegetable proteins. In this context, high moisture extrusion (HME) is an innovative technology, which requires more water, but milder temperatures than the more studied low moisture extrusion. The present thesis aimed at covering the current knowledge gap on this technology, by focusing on the flavor aspect of faba bean-based meat alternatives. The volatile profile of faba bean flour, protein concentrate, protein isolate, and mixtures was studied before and after high moisture extrusion by means of HS-SPME-GC-MS. Comparisons were made between raw materials (flour, protein concentrate, protein isolate, mixtures) and extrudates. The effect of the origin (Canadian and Finnish) of the protein concentrate was also investigated. Materials were also characterized for the following aspects: moisture, ash, protein, lipids, lipid-degrading enzymes (lipase and lipoxygenase), free amino acids, and free mono-, di-, and oligosaccharides. Several classes of volatile compounds were observed in both raw materials and extrudates, namely organic acids, alcohols, aldehydes, alkanes, alkenes, aromatic compounds, furans, esters, ketones, nitro compounds, and terpenes. Many compounds were characteristic of only one material, demonstrating that the formation of certain volatiles was product dependent. However, some other compounds were found in all materials, such as 1-hexanol, hexanal, and 2-pentylfuran. Literature addresses these compounds as responsible for the beany flavor. HME caused the inactivation of lipase and lipoxygenase but did not prevent the formation of lipid oxidation products. Products from Maillard reaction were not found in the extrudates. After HME, 1-hexanol levels decreased, whereas the abundance of 2-pentylfuran significantly increased. The behavior of hexanal after HME was less stable and predictable than the two beforementioned compounds. Not only these novel findings could have application in product development, but they also laid the basis for further research aimed at improving the flavor of faba bean.
  • Feijo Barreira, Luis Miguel; Duporte, Geoffroy; Rönkkö, Tuukka; Parshintsev, Jevgeni; Hartonen, Kari; Schulman, Lydia; Heikkinen, Enna; Jussila, Matti; Kulmala, Markku; Riekkola, Marja-Liisa (2018)
    Biogenic volatile organic compounds (BVOCs) emitted by terrestrial vegetation participate in a diversity of natural processes. These compounds impact both on short-range processes, such as on plant protection and communication, and on high-range processes, by e.g. participation on aerosol particle formation and growth. The biodiversity of plant species around the Earth, the vast assortment of emitted BVOCs, and their trace atmospheric concentrations contribute to the high remaining uncertainties about the effects of these compounds on atmospheric chemistry and physics, and call for the development of novel collection devices that can offer portability with improved selectivity and capacity. In this study, a novel solid-phase microextraction (SPME) Arrow sampling system was used for the static and dynamic collection of BVOCs from the boreal forest, and samples were subsequently analysed on-site by gas chromatography-mass spectrometry (GC-MS). This system offers higher sampling capacity and improved robustness than the traditional equilibrium-based SPME techniques, such as SPME fibers. Field measurements were performed in summer 2017 at the Station for Measuring Ecosystem-Atmosphere Relations (SMEAR II) in Hyytiälä, Finland. Complementary laboratory tests were also performed to compare the SPME-based techniques under controlled experimental conditions and to evaluate the effect of temperature and relative humidity on their extraction performance. The most abundant monoterpenes and aldehydes were successfully collected. A significant improvement on sampling capacity was observed with the new SPME Arrow system when compared to SPME fibers, with collected amounts being approximately 2 times higher for monoterpenes and 7-8 times higher for aldehydes. BVOC species exhibited different affinities for the type of sorbent materials used (PDMS/Carbon WR vs. PDMS/DVB). Higher extraction efficiencies were obtained with dynamic collection prior to equilibrium regime, but this benefit during the field measurements was small probably due to the natural agitation provided by the wind. An increase in temperature and relative humidity caused a decrease in the amounts of analytes extracted under controlled experimental conditions, even though the effect was more significant for PDMS/Carbon WR than for PDMS/DVB. Overall, results demonstrated the benefits and challenges of using SPME Arrow for the sampling of BVOCs in the atmosphere.
  • Wang, Aimei; Islam, Md Nahidul; Johansen, Anders; Haapalainen, Minna; Latvala, Satu; Edelenbos, Merete (2019)
    Diseases develop during the storage of onions. To minimize losses, new methods are needed to identify diseased bulbs early in storage. Volatile organic compounds (VOCs), the respiration rate, weight loss, and the dry matter content were investigated for 1-7 weeks post inoculation of bulbs with water (control) and two strains (Fox006 or Fox260) of Fusarium oxysporum f. sp. cepae. Photos, multispectral image analysis, and real-time polymerase chain reaction (PCR) showed no infection in the control onions, weak pathogenic infection in Fox006-onions, and strong pathogenic infection in Fox260-onions at week 7 post inoculation. Infected bulbs exhibited increased respiration rate, increased VOC emission rate, and increased weight loss. The control and Fox006-onions did not respond to inoculation and had similar reaction pattern. Forty-three different VOCs were measured, of which 17 compounds had sulfur in their chemical structure. 1-Propanethiol, methyl propyl sulfide, and styrene were emitted in high concentrations and were positively correlated with the extent of infection (r = 0.82 - 0.89). Therefore, these compounds were the most promising volatile markers of Fusarium basal rot infection. For the first time, we show that the extent of fungal infection determined by real-time PCR in onion bulbs is related with VOC emission.