Novel, rapid, low-cost screen-printed (bio)sensors for the direct analysis of boar taint compounds androstenone and skatole in porcine adipose tissue: Comparison with a high-resolution gas chromatographic method.

This is the first report on the fabrication, characterisation and application of an electrochemical (bio)sensor system for the simultaneous measurement of skatole and androstenone. A biosensor for androstenone was fabricated using a Meldola's Blue modified SPCE (MB-SPCE) by depositing NADH and the enzyme 3α-hydroxysteroid dehydrogenase onto the MB-SPCE surface; samples of adipose tissue were analysed using the biosensors in conjunction with chronoamperometry. Cyclic voltammetry was used to investigate the electrochemical behaviour of skatole at a screen-printed carbon electrode (SPCE vs. Ag/AgCl). An oxidation peak was observed around +0.55 V (vs. Ag/AgCl) and differential pulse voltammetry was applied for quantification of skatole in adipose tissue (in-situ). Quantitative analysis was achieved using calibration plots obtained from fortified meat samples. The concentrations obtained by the electrochemical and gas chromatographic (GC) methods demonstrated a good positive correlation. The (bio)sensor system completed both measurements within 60 s, as compared to several hours for GC, and at a considerably reduced cost and complexity. Consequently, the novel (bio)sensor system should have applications for analysis of carcasses on the abattoir processing line.

Characterization of 3-Methylindole as a Source of a "Mud"-like Off-Odor in Strong-Aroma Types of Base Baijiu.

The "mud"-like off-odor, which is an odor reminiscent of musty and strong animal fecal odors, affects the quality classification of the strong-aroma types of baijiu (SAB), but little is known about which compounds are responsible for this aroma, except for certain phenolic compounds. However, not all mud-like off-odor expressions in SAB can be attributed to those phenolic compounds. In this work, volatile compounds in pit mud and SAB samples were isolated by headspace solid-phase microextraction and liquid-liquid extraction. An odoriferous zone was detected by GC-MS/olfactometer and GC-MS and was attributed to 3-methylindole rather than ethyl oleate on the basis of their odor characteristics, MS data, and retention indices. Combined with the detection threshold of 3-methylindole determined by a three-alternative forced-choice (6.09 µg/L) procedure, odor activity values in the tested base SAB were from 1 to 23. Sensory studies and the prepared heat map highlighted the contribution of this compound to the odor characteristics for the first time.

Characteristic Scent from the Tahitian Liverwort, Cyathodium foetidissimum.

The volatile components of the Tahitian liverwort Cyathodium foetidissimum was analyzed using headspace solid phase micro-extraction (SPME) and GC-MS. Three volatile components, 4-methoxystyrene (24.4%), 3,4-dimethoxystyrene (28.7%), and skatole (15.9%) were identified as the major components from the fresh C. foetidissimum, along with several aliphatic aldehydes, n-octanal, n-nonanal, and n-decanal. However, (E)-2-nonenal recognized as aged malodor was not identified. In GC-O analysis, 2-aminoacetophenone was detected as one of the minor components with a strong aging note. In fact, C. foetidissimum showed the characteristic aging odor reminiscent the damp smell from old chest of drawers, or the civet like note with very strong feces and urine odor. The mixture consisted of 4-methoxystyrene, 3,4-dimethoxystyrene, and skatole in the detected ratio showed the sedative effect on CNV (contingent negative variation) measurement.

Rapid method for the simultaneous detection of boar taint compounds by means of solid phase microextraction coupled to gas chromatography/mass spectrometry.

Because of animal welfare issues, the voluntary ban on surgical castration of male piglets, starting January 2018 was announced in a European Treaty. One viable alternative is the fattening of entire male pigs. However, this can cause negative consumer reactions due to the occurrence of boar taint and possibly lead to severe economic losses in pig husbandry. In this study, headspace solid phase microextraction (HS-SPME) coupled to GC-MS was used in the development and optimization of a candidate method for fast and accurate detection of the boar taint compounds. Remarkably fast extraction (45s) of the boar taint compounds from adipose tissue was achieved by singeing the fat with a soldering iron while released volatiles were extracted in-situ using HS-SPME. The obtained method showed good performance characteristics after validation according to CD 2002/657/EC and ISO/IEC 17025 guidelines. Moreover, cross-validation with an in-house UHPLC-HR-Orbitrap-MS method showed good agreement between an in-laboratory method and the new candidate method for the fast extraction and detection of skatole and androstenone, which emphasizes the accuracy of this new SPME-GC-MS method. Threshold detection of the boar taint compounds on a portable GC-MS could not be achieved. However, despite the lack of sensitivity obtained on the latter instrument, a very fast method with run-to-run time of 3.5min for the detection of the boar taint compounds was developed.

Chemical composition, aroma evaluation, and oxygen radical absorbance capacity of volatile oil extracted from Brassica rapa cv. "yukina" used in Japanese traditional food.

The chemical composition of the volatile oil extracted from the aerial parts of Brassica rapa cv. "yukina" was analyzed using GC-MS, GC-PFPD, and GC-O. A total of 50 compounds were identified. The most prominent constituents were (E)-1,5-heptadiene (40.27%), 3-methyl-3-butenenitrile (25.97%) and 3-phenylpropanenitrile (12.41%). With regard to aroma compounds, 12 compounds were identified by GC-O analysis. The main aroma-active compounds were dimethyl tetrasulfide (sulphury-cabbage, FD = 64), 3-phenylpropanenitrile (nutty, FD = 64), 3-methylindole (pungent, FD = 64), and methional (potato, FD = 32). The antioxidant activity of the aroma-active compounds of the oil was determined using an oxygen radical absorbance capacity (ORAC) assay using fluorescein as the fluorescent probe. The ORAC values were found to be 785 ± 67 trolox equivalents (µmol TE/g) for B. rapa cv. "yukina" oil. The results obtained showed that the volatile oil extracted from the aerial parts is a good dietary source of antioxidants.

Development of a candidate reference method for the simultaneous quantitation of the boar taint compounds androstenone, 3α-androstenol, 3ß-androstenol, skatole, and indole in pig fat by means of stable isotope dilution analysis-headspace solid-phase microextraction-gas chromatography/mass spectrometry.

The steroidal pig pheromones androstenone (5α-androst-16-en-3-one), 3α-androstenol (5α-androst-16-en-3α-ol), and 3ß-androstenol (5α-androst-16-en-3ß-ol) as well as the heterocyclic aromatic amines skatole and indole, originating from microbial degradation of tryptophan in the intestine of pigs, are frequently recognized as the major compounds responsible for boar taint. A new procedure, applying stable isotope dilution analysis (SIDA) and headspace solid-phase microextraction-gas chromatography/mass spectrometry (HS-SPME-GC/MS) for the simultaneous quantitation of these boar taint compounds in pig fat was developed and validated. The deuterated compounds androstenone-d(3), 3ß-androstenol-d(3), skatole-d(3), and indole-d(6) were synthesized and successfully employed as internal standards for SIDA. The new procedure is characterized by a fast, simple, and economic sample preparation: methanolic extraction of the melted fat followed by a freezing and an evaporation step allows for extraction and enrichment of all five analytes. Additional time-consuming cleanup steps were not necessary, as HS-SPME sampling overcomes fat-associated injector and column contamination. The method has been validated by determining intra- and interday precision and accuracy as well as the limit of detection (LOD) and limit of quantitation (LOQ). Additionally, a cross-validation for androstenone, skatole, and indole was carried out comparing the results of 25 back fat samples obtained simultaneously by the new SIDA-HS-SPME-GC/MS procedure with those obtained in separate GC/MS and high-performance liquid chromatography fluorescence detection (HPLC-FD) measurements. The cross-validation revealed comparable results and confirms the feasibility of the new SIDA-HS-SPME-GC/MS procedure.

Semiochemicals of the Scarabaeinae: VI. Identification of EAD-active constituents of abdominal secretion of male dung beetle, Kheper nigroaeneus.

Using gas chromatography with flame ionization detection (FID) and electroantennographic detection (EAD) in parallel, and employing chiral and achiral capillary columns, three constituents of the abdominal sex-attracting secretion of male Kheper nigroaeneus dung beetles were found to elicit reproducible EAD responses in male and female K. nigroaeneus antennae. One of these constituents is present in the secretion in such a small quantity that it could not be detected by FID, and it was not identified. The other constituents were identified as 3-methylindole (skatole) and (R)-(+)-3-methylheptanoic acid.

Identification of skatolyl hydroperoxide and its role in the peroxidase-catalysed oxidation of indol-3-yl acetic acid.

Indol-3-yl acetic acid (IAA, auxin) is a plant hormone whose degradation is a key determinant of plant growth and development. The first evidence for skatolyl hydroperoxide formation during the plant peroxidase-catalysed degradation of IAA has been obtained by electrospray MS. Skatolyl hydroperoxide degrades predominantly non-enzymically to oxindol-3-yl carbinol but in part enzymically into indol-3-yl methanol via a peroxidase cycle in which IAA acts as an electron donor. Skatolyl hydroperoxide is degradable by catalase. Horseradish peroxidase isoenzyme C (HRP-C) and anionic tobacco peroxidase (TOP) exhibit differences in their mechanisms of reaction. The insensitivity of the HRP-C-catalysed reaction to catalase is ascribed to the formation of HRP-C Compound III at the initiation step and its subsequent role in radical propagation. This is in contrast with the TOP-catalysed process in which skatolyl hydroperoxide has a key role. Indol-3-yl aldehyde is produced not via the peroxidase cycle but by catalysis involving ferrous peroxidase. Because indol-3-yl aldehyde is one of the main IAA-derived products identified in planta, we conclude that ferrous peroxidases participate in IAA catalytic transformations in vivo. A general scheme for peroxidase-catalysed IAA oxidation is presented.