Browsing by Subject "SPME-GC-MS"

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  • Kamlang-ek, Pimwalee (Helsingfors universitet, 2012)
    The literature survey reviewed principles of oxidation of edible oils, adverse effects of lipid oxidation and analysis of volatile oxidation products by SPME-GC-MS. The main aim of the experimental research was to study the influence of relative humidity (RH) on the release of volatile oxidation products from spray-dried emulsions with natural and cross-linked casein as emulsifier. The release of volatiles was determined by SPME-GC-MS. The sub aims were to study the effects of stabilization time at specific RHs, of temperature and agitation speed during the SPME extraction. The spray-dried emulsions were oxidised at 40oC in order to reach a certain level of oxidation. Next, the powders were stabilised under five RHs (0%, 11%, 33%, 54% and 75%) for one or two weeks in order to observe the effect of the RH and the stabilisation time on the release of volatiles. After adjusting the RHs, volatile compounds were analysed by SPME-GC-MS. The following SPME extraction conditions were tested: C1: temperature 40oC, agitation speed 250 rpm, C2: 50oC, 250 rpm, C3: 40oC, 500 rpm and C4: 50oC, 500 rpm. Identification of the compounds was carried out by matching their MS spectra with the NIST database. Altogether 45 volatiles released from the powders could be identified, and 18 of them were found in most samples. RH had an important effect on the release of volatiles from the encapsulated samples. The highest release was always observed at 11% and 33% RH, whereas the lowest release was found at 0% and/or 75% RH, depending on the SPME extraction conditions. The stabilisation time did not have a significant effect on the release of volatiles in most RHs. During the SPME extraction step, elevation of the temperature from 40oC to 50oC, as well as the agitation speed from 250 rpm to 500 rpm, facilitated higher release. However, the effect of temperature was greater than that of agitation speed. Although it was suspected that cross-linking of sodium-caseinate would enhance retention of volatiles, our experiment showed greater peak areas of most volatiles from the cross-linked samples than from the natural ones. By controlling the SPME parameters, it was possible to obtain repeatable volatile compound results. The SPME-GC-MS method applied in this study can be reliably used to analyse volatile oxidation products from spray-dried emulsions. Only at very low or high RH the release of volatiles may differ from samples stored at 11% -54% RH.
  • Malinen, Hanna (Helsingfors universitet, 2016)
    In the literature study paper manufacturing process and modification of wood fiber-based packaging materials were reviewed. The aim was to understand the properties of polyurethane (PU) and its suitability as an additive in fiber-based food packaging material. Also possibility of migration from food packaging materials and methods of migration analysis were reviewed. The aim of the experimental work was to examine if diisocyanates, phthalates or other substances migrate significantly from PU-impregnated wood fiber-based packaging material to cheese. The impact of storage conditions such as temperature, relative humidity (RH) and storage time on migration were examined. The base of the sample package was made of PU-impregnated fiber material (VTT Oy, Finland) and the cover film was BoPET/PE/PA/EvOH/PE-laminate (Wipak Oy, Finland). Slices of pasteurized hard Cheddar cheese (Wyke Farms Mature Cheddar, England) were packaged as samples. Migration was measured from the surface of the packaging materials and cheese using attenuated total reflection Fourier-transform infrared spectrometer (ATR-FT-IR) and from the head space of the samples using solid-phase microextraction coupled with gas chromatography and mass spectrometer (SPME-GC-MS). No diisocyanates were detected in any packaging material or cheese samples with either methods. A notable peak in the mass spectra of samples containing or having been in contact with PU was caused by 1,6-dioxacyclododecane-7,12-dione. Also one phthalate, diethyl phthalate (DEP) was detected with SPME-GC-MS in some of the samples. The peak areas of DEP decreased after two weeks storage at 10 °C, RH 56 % and 5 °C, RH 90 %, except for cheese. After four weeks storage under the warmest conditions (10 °C, RH 56 %) the peak areas increased for all the samples but decreased at the highest RH (90 %) for PU-fiber and the cheese in it. DEP was detected in almost every cheese sample packed in PU-fibre. DEP was also detected in fiber without PU. No diisocyanates or phthalates classified as harmful to human health were detected in this study. Based on the results of this migration study PU-impregnated fiber material would be safe to use in contact with food.