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The assessment of olfactory function is becoming increasingly relevant, especially in cases of cognitive decline (i.e., neurodegenerative diseases), where olfactory alterations may be relevant as potential early biomarkers. The Sniffin’ Sticks Olfactory Test, developed in Germany and validated in several countries, is an objective measure of olfactory performance. This study aims to validate this test in a Spanish sample. This study included 209 healthy normosmic volunteers (154 females and 55 males) aged between 20 to 79 years (mean age = 50.11 ± 15.18 years) as the normative sample. From this group, 22 participants were retested in order to obtain test–retest reliability evidence. Odor familiarity for descriptors in the olfactory identification test was also studied on an independent healthy sample (n = 69), and required cultural modifications were applied. Results indicate that men and women, as well as smokers and non-smokers, performed equally in every test. However, significant differences were found between age groups in every score. The general trend is that olfactory function progressively decreases as a function of age, the elderly group (+60 years) being the one with the lowest scores. In conclusion, this normative data, in addition to the test’s cultural modifications, allows the Sniffin’ Sticks Olfactory Test to be administered on a Spanish population.

The volatile compounds found in melons (Cucumis melo L.) obtained from three cultivars [Jiashi (JS), Xizhoumi17 (XZM) and Minqin (MQ)] were comprehensively analyzed by gas chromatography−olfactometry (GC–O), gas chromatography−mass spectrometry (GC–MS), and GC-flame photometric detection (GC-FPD). The result showed that 46, 45 and 69 volatile compounds were detected in XZM, JS and MQ samples by GC–MS, respectively. Besides, 6, 8 and 9 sulfur compounds were detected by GC-FPD, respectively. Dimethyl sulfide, 1-propanethiol, 3-mercapto-3methylbutanol, 3-methyl-2-buten-1-thiol were detected for the first time in melon. 25 key aroma compounds were identified in MQ muskmelon by omission tests, among which (Z)-6-nonenal, (Z)-6-nonen-1-ol, 3-methylbutanal, 2-methylbutyl acetate, hexanal and methyl thioacetate were particularly important. The interaction between three aroma compounds containing nine-carbon straight-chain structure and five thioesters in MQ muskmelon was studied by comparing their olfactory threshold and OAV values. Among the 18 binary mixtures, 8 mixtures showed a synergistic effect, 2 mixtures presented an additive effect, 2 mixtures showed no interaction, 6 mixtures exhibited a masking effect. There is a synergistic effect between (Z)-6-nonenal, (Z)-6-nonen-1-ol and (E, Z)-3,6-nonadien-1-ol, the aroma intensity of the mixture can be predicted by modified vector model.

Retronasal aroma strongly influences the flavor quality of low-alcohol Jiangxiangxing Baijiu. This study investigated the retronasal aroma differences between high- and low-alcohol samples (Sample-High and Sample-Low). Dynamic sensory evaluation revealed roasted, grain, floral and fruity, hay, and caramel notes were more pronounced in Sample-High, whereas Sample-Low exhibited stronger fatty and smoky notes, indicating insufficient retronasal aroma richness in Sample-Low. Analysis of 67 compounds showed no significant concentration differences, yet their retronasal olfactory thresholds varied markedly between alcoholic systems (ratio 1.04–4.75), leading to higher dose-over-threshold (DoT) values for several compounds in Sample-Low. Further analysis of the DoT distribution intervals showed Sample-High presented a more balanced distribution, whereas Sample-Low was strongly driven by several high-contribution compounds, which reduced the relative contributions of others. This unbalanced distribution may underlie the lower retronasal aroma richness observed in Sample-Low. These findings provide a new perspective for understanding retronasal aroma in low-alcohol Jiangxiangxing Baijiu.

The association between smell impairment and chronic diseases has been reported in some studies in adults. Such information is not available for chronic diseases in children. The aim of this study was to examine olfactory function of children with chronic diseases such as diabetes mellitus type 1, hypothyroidism, and bronchial asthma in combination with allergic rhinitis in comparison to healthy controls. The data were obtained from n = 205 participants (104 boys, 101 girls) between the age of 6 and 17 years. Seventy-eight of the participants were healthy controls, n = 43 had diabetes mellitus type 1, n = 50 suffer from allergic rhinitis or bronchial asthma, and 34 presented a reduced function of their thyroid in medical history. All participants underwent olfactory testing including olfactory threshold using “Sniffin’ Sticks” and odor identification using the “U-Sniff” test. In addition, a depression inventory and cognitive testing using the Ravens Progressive Matrices was performed. No significant difference in olfactory function was observed for any of the chronic diseases in children in comparison to healthy controls. Further analysis showed a trend in significance for a subpopulation of children with bronchial asthma and comorbidities performed worse on the olfactory threshold test compared to patients with bronchial asthma without comorbidities. Pediatric patients suffering from chronic diseases scored higher on the depression inventory compared to healthy controls.Conclusion: In conclusion, this study demonstrates that the influence of chronic diseases (bronchial asthma, diabetes mellitus type 1 and hypothyroidism) on olfactory function in childhood, if any, seems to be insignificant. This is partly in contrast to adult patients. Further research should be conducted in a subgroup of patients with bronchial asthma, allergic rhinitis, and atopic dermatitis or other comorbidities to better understand the association of allergic diathesis and olfactory function and the putative pathogenesis of olfactory dysfunction.What is known:• The association between smell impairment and chronic diseases has been reported in some studies in adults.• Such information is not available for chronic diseases in children.What is new:• The influence of chronic diseases (bronchial asthma, diabetes mellitus type 1, and hypothyroidism) on olfactory function in childhood, if any, seems to be insignificant.• In patients with bronchial asthma and allergic rhinitis, only a subgroup of patients with additional comorbidity (atopic dermatitis) showed a tendency to a reduced sense of smell.

2-methylisoboneol (2-MIB) and geosmin are two typical earthy-musty odour compounds in freshwater. In order to investigate the olfactory thresholds of 2-MIB and geosmin in black carp (Mylopharyngodon piceus) and bighead carp (Hypophthalmichthys nobilis), an improved and optimized pre-treatment method of adsorbing the earthy-musty odours combined with the technology of gas chromatography following microwave distillation-headspace solid-phase microextraction was developed. The fish back muscle samples were placed in vials with the 2-MIB/geosmin solution and reached the adsorption equilibrium. Some samples were evaluated by a panel of ten members using Flavour Profile Analysis (FPA) method, the remaining sample was used for instrumental analysis. In fish muscle blocks, it took 90 and 105 min to establish the absorption equilibrium of 2-MIB and geosmin, respectively. The olfactory thresholds of 2-MIB in the bodies of black carps and bighead carps were 0.35 μg/kg and 0.30 μg/kg, respectively, while the geosmin thresholds were 0.59 μg/kg and 0.51 μg/kg, respectively. The concentrations of 2-MIB and geosmin in the bodies of black carps were slightly higher than in bighead carps, which were probably caused by the differences in the body fat content and the volatility of 2-MIB and geosmin.

Alcohols and esters are core flavor-active constituents of Qingxiangxing Baijiu (QXB), yet ethanol concentration's regulatory role in their thresholds and interactions remains unclear. Physicochemical analysis showed reduced-alcohol QXB (L-QX, 42%, / ) had higher total acid (1.48 g/L) but lower total ester (1.52 g/L) than high-alcohol QXB (H-QX, 53%, / ; 1.20 g/L total acid, 2.05 g/L total ester). Sensory evaluation (0-5 scale) revealed H-QX had higher fruity (3.6 vs. 2.0), grassy (3.2 vs. 1.8), and grainy (3.0 vs. 1.9) aroma scores, while L-QX showed higher sour (2.1 vs. 1.5) and lees (1.7 vs. 1.1) notes ( < 0.05). The quantification of gas chromatography-flame ionization detection (GC-FID) determined the concentrations of eight alcohols and esters in H-QX samples and identified that most flavor compounds had higher concentrations than L-QX samples. Three alternative forced-choice tests showed 53% ethanol elevated olfactory thresholds (OTs) of five compounds, with ethyl lactate (1.53-fold) and isopentanol (1.89-fold) vs. 42%. For 16 alcohol-ester binary mixtures, 12 pairs had OT ratios (53% vs. 42%) < 1, especially 3 pairs (e.g., n-propanol-ethyl acetate) < 0.5. OAV/S curve analyses indicated all 16 mixtures had masking effects, with 11 pairs stronger at 42%. Verification validated 53% ethanol mitigated masking, enhancing fruity/grassy aromas by 38.1%/25.0%. This study provides support for QXB dealcoholization flavor regulation.

Decrease of olfactory function in Parkinson's disease (PD) is a well-investigated fact. Studies indicate that pharmacological treatment of PD fails to restore olfactory function in PD patients. The aim of this investigation was whether patients with PD would benefit from \"training\" with odors in terms of an improvement of their general olfactory function. It has been hypothesized that olfactory training should produce both an improved sensitivity towards the odors used in the training process and an overall increase of olfactory function. We recruited 70 subjects with PD and olfactory loss into this single-center, prospective, controlled non-blinded study. Thirty-five patients were assigned to the olfactory training group and 35 subjects to the control group (no training). Olfactory training was performed over a period of 12 weeks while patients exposed themselves twice daily to four odors (phenyl ethyl alcohol: rose, eucalyptol: eucalyptus, citronellal: lemon, and eugenol: cloves). Olfactory testing was performed before and after training using the \"Sniffin' Sticks\" (thresholds for phenyl ethyl alcohol, tests for odor discrimination, and odor identification) in addition to threshold tests for the odors used in the training process. Compared to baseline, trained PD patients experienced a significant increase in their olfactory function, which was observed for the Sniffin' Sticks test score and for thresholds for the odors used in the training process. Olfactory function was unchanged in PD patients who did not perform olfactory training. The present results indicate that olfactory training may increase olfactory sensitivity in PD patients.

Since its apomorphic appearance in 2019, severe acute respiratory syndrome Coronavirus type 2 (SARS-CoV-2) nowadays circulates as a plesiomorphic human virus in several synapomorphic variants. The respiratory tract is the most important site of infection, the viral effects in the lungs are well described, and more than half of the patients could develop shortness of breath and dyspnea and require ventilatory support. The physiological sign of this condition is the decrease in the partial pressure of oxygen in the blood, leading to acute hypoxia, which could be a factor in the disease. In severe patients, we recorded several physiological parameters: breath frequency (BF), partial pressure of oxygen in the blood (pO2), partial pressure of carbon dioxide in the blood (pCO2), hemoglobin (Hb), heart rate (HR), and blood pressure in correlation with the olfactory threshold. We found significant correlations between reduced olfactory threshold with pO2 and hemoglobin levels, changes in heart rate, and increased HR and pCO2. These results suggest that COVID-19 causes an impaired sense of smell that decreases in threshold corresponding to the disease severity.

The canine olfactory system is a highly efficient and intricate tool often exploited by humans for detection for its many attributes, including impressive sensitivity to trace analyte vapors. Canine detectors are often touted as having lower limits of detection, or olfactory detection threshold (ODT), than other field-relevant detection technologies; however, previous attempts to quantify canine ODTs have resulted in reported estimates spanning multiple orders of magnitude, even for the same analyte. A major contributor to these discrepancies is the vapor delivery method used for testing, where losses due to adsorption and dilution are often unaccounted for, and the presence of unattended compounds in the vapor stream due to carryover may go unnoticed. In this research, a trace vapor generator (TV-Gen) was used to deliver quantitatively accurate amounts of vapor reproducibly over time for canine testing. Analyte losses due to adsorption to surfaces in the flow path, dilution in the sniff port at the outlet, and analyte carryover were considered. Computational fluid dynamic (CFD) modeling was used to visualize analyte vapor spread throughout the port. CFD simulations revealed the need for a diffuser to encourage the diffusion of the analyte throughout the port. As a result, the modified vapor generator provides analyte air as a diffuse flow that is evenly distributed through the custom sampling orifice, as opposed to a narrow stream of air at the chosen concentration which exits directly into the environment. Laboratory validations were carried out for three analytes, amyl acetate, 2,4-dinitrotoluene (DNT), and methyl benzoate. A linear response across more than two orders of magnitude vapor concentration range was achieved for all analytes. These efforts will be applied in further research utilizing this TV-Gen vapor delivery system for canine ODT testing, eliminating many quantitative changes seen previously.

Subjective cognitive decline (SCD) is a high‐risk population in the preclinical stage of Alzheimer's disease (AD), and olfactory dysfunction is a risk factor for dementia progression. The present study aimed to explore the patterns of functional connectivity (FC) changes in the olfactory neural circuits during olfactory stimulation in SCD subjects. A total of 56 SCD subjects and 56 normal controls (NCs) were included. All subjects were assessed with a cognitive scale, an olfactory behavior test, and olfactory task‐based functional magnetic resonance imaging scanning. The FC differences in olfactory neural circuits between the two groups were analyzed by the generalized psychophysiological interaction. Additionally, we calculated and compared the activation of brain regions within the olfactory neural circuits during odor stimulation, the volumetric differences in brain regions showing FC differences between groups, and the correlations between neuroimaging indicators and olfactory behavioral and cognitive scale scores. During odor stimulation, the FC between the bilateral primary olfactory cortex (bPOC) and the right hippocampus in the SCD group was significantly reduced; while the FC between the right hippocampus and the right frontal cortex was significantly increased in the SCD group. The bPOC of all subjects showed significant activation, but no significant difference in activation between groups was found. No significant differences were observed in the volume of the brain regions within the olfactory neural circuits or in olfactory behavior between groups. The volume of the bPOC and right frontal cortex was significantly positively correlated with olfactory identification, and the volume of the right frontal cortex and right hippocampus was significantly correlated with cognitive functions. Furthermore, a significant correlation between the activation of bPOC and the olfactory threshold was found in the whole cohort. These results suggested that while the structure of the olfactory neural circuits and olfactory behavior in SCD subjects remained stable, there were significant changes observed in the FC of the olfactory neural circuits (specifically, the POC‐hippocampus‐frontal cortex neural circuits) during odor stimulation. These findings highlight the potential of FC alterations as sensitive imaging markers for identifying high‐risk individuals in the early stage of AD. Our findings showed that during odor stimulation, the subjective cognitive decline group exhibited significantly reduced functional connectivity (FC) between the bilateral primary olfactory cortex and the right hippocampus compared to the normal control group. Conversely, there was a significantly enhanced FC between the right hippocampus and the right frontal cortex.