Halogenated phenols and cresols belong to a group of volatiles consistently reported as off-flavour compounds. For example, 2-iodophenol and 2-iodo-4-methylphenol with their typical medicinal smell were found to negatively affect bottled mineral water. Even though these compounds are widespread in nature no comprehensive information about their chemo-analytical as well as odour properties is available. Therefore, the objective of this study were (1) to provide systematic chemo-analytical data on these substances, such as mass spectral data and retention parameters in gas chromatographic analysis, and (2) to determine, on a direct comparative basis, the sensory properties of eight mono-halogenated phenols, four di-halogenated phenols and four halogenated cresols. Evaluations focused on the determination of odour quality and odour threshold concentration in air and water. With regard to the relationship between substitution pattern and odour character, the location of an iodine atom in the ortho-position was demonstrated to obviously be an important prerequisite for medicinal, plaster-like or ink-like smell. Faecal or horse stable-like odour notes were predominantly related to compounds being substituted either by halogen moieties or by a methyl group in the para-position. The 2-halogenated 4-methylphenols were found to be the odorants with the lowest odour threshold concentrations of all the compounds investigated in this study, and that, generally, compounds with ortho-halogenation exhibited exceptionally low odour threshold concentrations
A specific mineral water off-odor, the so-called “sunlight” flavor produced after UV light exposure, was characterized by sensory analysis in different mineral water samples and ranked according to overall odor intensity. The odorants were isolated by means of solvent extraction and stir bar sorptive extraction (SBSE) techniques, respectively. Analyses were performed with two-dimensional (2D) high resolution gas chromatographic (HRGC) separation and parallel mass spectrometric (MS) and olfactometric (O) detection. Additionally, analyses of off-odor-free samples exposed to natural sunlight or to “artificial” UV radiation (replicating natural sunlight) were analyzed to assess off-odor compound formation. 14 common characteristic odorants in commercial off-odor and irradiated samples were identified. These were predominantly saturated and mono or di-unsaturated carbonyl compounds, with several substances exhibiting the characteristic fatty and plastic-like odor impressions. Eight of the compounds identified were detected for the first time as off-odor “sunlight” flavor contributors to mineral water and had amongst the highest flavor dilution (FD) factors in the extracted samples.
Combinations of enzymatic hydrolysis using different proteolytic enzymes (papain, Esperase®, trypsin) and lactic fermentation with Lactobacillus plantarum were used to alter potential pea allergens, the functional properties and sensory profile of pea protein isolate (PPI). The order in which the treatments were performed had a major impact on the changes in the properties of the pea protein isolate; the highest changes were seen with the combination of fermentation followed by enzymatic hydrolysis. SDS-PAGE, gel filtration, and ELISA results showed changes in the protein molecular weight and a reduced immunogenicity of treated samples. Treated samples showed significantly increased protein solubility at pH 4.5 (31.19–66.55%) and at pH 7.0 (47.37–74.95%), compared to the untreated PPI (6.98% and 40.26%, respectively). The foaming capacity was significantly increased (1190–2575%) compared to the untreated PPI (840%). The treated PPI showed reduced pea characteristic off-flavors, where only the treatment with Esperase® significantly increased the bitterness. The results from this study suggest that the combination of enzymatic hydrolysis and lactic fermentation is a promising method to be used in the food industry to produce pea protein ingredients with higher functionality and a highly neutral taste. A reduced detection signal of polyclonal rabbit anti-pea-antibodies against the processed protein preparations in ELISA furthermore might indicate a decreased immunological reaction after consumption.
The present study simulated large-scale indoor mold damage in order to test the efficiency of air sampling for the detection of microbial volatile organic compounds (MVOCs). To do this, a wallpaper damaged by condensation was stored in a climate chamber (representing a hypothetical test room of 40 m(3) volume) and was inoculated with 14 typical indoor fungal strains. The chamber ventilation conditions were adjusted to common values found in moldy homes, and the mold growth was allowed to continue to higher than average values. The MVOC content of the chamber air was analyzed daily for a period of 105 days using coupled gas chromatography/mass spectrometry (GC-MS). This procedure guarantees MVOC profiling without external factors such as outdoor air, building materials, furniture, and occupants. However, only nine MVOCs could be detected during the sampling period, which indicates that the very low concentrated MVOCs are hardly accessible, even under these favorable conditions. Furthermore, most of the MVOCs that were detected cannot be considered as reliable indicators of mold growth in indoor environments.
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