Sensory properties of rehydrated Toona sinensis shoots after dehydrated by different drying methods and association with gamma-glutamyl transferase reaction.

Sulfur-containing compounds are responsible for the aroma of Toona sinensis shoot (TS). In this study, vacuum-freeze-drying (VFD), microwave-drying (MD), and hot-air-drying at 100 and 40 °C (HAD100 and HAD40, respectively), were applied to dehydrate perishable TS for preservation. VFD-TS retained most aroma of fresh/raw TS after rehydration. The content of sulfur-containing compounds reached to 118.00 µg/g with leading by methyl thiirane, (E,E)/(E,Z)/(Z,Z)-bis-(1-propenyl) disulfides, and (Z)/(E)-2-mercapto-3,4-dimethyl-2,3-dihydrothiophenes accounting for 86.33 %. They were undetected in the rehydrated MD-TS and HAD100-TS, as the indigenous enzymes in TS were deactivated under their dehydration conditions. Interestingly, the sulfur-containing compounds was restored by 77.47 % after the TS was treated by gamma-glutamyl transferase (GGT). Thus, the release of sulfur-containing compounds from TS could depend on GGT reaction. It was different from alliaceous vegetables relying on alliinase reaction. The results revealed the aroma formation in TS and provided an approach to enhance the aroma of TS dried by different methods.

Nanozyme sensor array based on Fe, Se co-doped carbon material for the discrimination of Sulfur-containing compounds.

Developing methods for the accurate identification and analysis of sulfur-containing compounds (SCCs) is of great significance because of their essential roles in living organisms and the diagnosis of diseases. Herein, Se-doping improved oxidase-like activity of iron-based carbon material (Fe-Se/NC) was prepared and applied to construct a four-channel colorimetric sensor array for the detection and identification of SCCs (including biothiols and sulfur-containing metal salts). Fe-Se/NC can realize the chromogenic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by activating O2 without relying on H2O2, which can be inhibited by different SCCs to diverse degrees to produce different colorimetric response changes as "fingerprints" on the sensor array. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) revealed that nine kinds of SCCs could be well discriminated. The sensor array was also applied for the detection of SCCs with a linear range of 1-50 µM and a limit of detection of 0.07-0.2 µM. Moreover, colorimetric sensor array inspired by the different levels of SCCs in real samples were used to discriminate cancer cells and food samples, demonstrating its potential application in the field of disease diagnosis and food monitoring. ENVIRONMENTAL IMPLICATIONS: In this work, a four-channel colorimetric sensor array for accurate SCCs identification and detection was successfully constructed. The colorimetric sensor array inspired by the different levels of SCCs in real samples were also used to discriminate cancer cells and food samples. Therefore, this Fe-Se/NC based sensor array is expected to be applied in the field of environmental monitoring and environment related disease diagnosis.

Release characteristics and risk assessment of volatile sulfur compounds in a municipal wastewater treatment plant with odor collection device.

Due to the malodorous effects and health risks of volatile sulfur compounds (VSCs) emitted from wastewater treatment plants (WWTPs), odor collection devices have been extensively utilized; however, their effectiveness has rarely been tested. In the present investigation, the characteristics of VSCs released in a WWTP equipped with gas collection hoods are methodically examined by gas chromatography. The obtained results indicate that the concentration of VSCs in the ambient air can be substantially reduced, and the primary treatment unit still achieves the highest concentration of VSCs. Compared to WWTPs without odor collection devices, the concentration of H2S in this WWTP is not dominant, but its sensory effects and health risks are still not negligible. Additionally, research on the emission of VSCs from sludge reveals that the total VSCs emitted from dewatering sludge reaches the highest level. Volatile organic sulfur compounds play a dominant role in the component and sensory effects of VSCs released by sludge. This study provides both data and theoretical support for analyzing the effectiveness of odor collection devices in WWTPs, as well as reducing the source of VSCs. The findings can be effectively employed to optimize these devices and improve their performance.

A structural color hydrogel for diagnosis of halitosis and screening of periodontitis.

Oral pathogens can produce volatile sulfur compounds (VSCs), which is the main reason for halitosis and indicates the risk of periodontitis. High-sensitivity detection of exhaled VSCs is urgently desired for promoting the point-of-care testing (POCT) of halitosis and screening of periodontitis. However, current detection methods often require bulky and costly instruments, as well as professional training, making them impractical for widespread detection. Here, a structural color hydrogel for naked-eye detection of exhaled VSCs is presented. VSCs can reduce disulfide bonds within the network, leading to expansion of the hydrogel and thus change of the structural color. A linear detection range of 0-1 ppm with a detection limit of 61 ppb can be achieved, covering the typical VSC concentration in the breath of patients with periodontitis. Furthermore, visual and in situ monitoring of Porphyromonas gingivalis responsible for periodontitis can be realized. By integrating the hydrogels into a sensor array, the oral health conditions of patients with halitosis can be evaluated and distinguished, offering risk assessment of periodontitis. Combined with a smartphone capable of color analysis, POCT of VSCs can be achieved, providing an approach for the monitoring of halitosis and screening of periodontitis.

Comprehensive metabolite and biological profile of "Sulmona Red Garlic" ecotype's aerial bulbils.

"Sulmona Red Garlic" is a well-known Italian traditional product. Bulbs, used for culinary purposes, have been largely investigated for their medicinal properties whereas aerial bulbils are usually removed as waste material. Here, for the first time, chemical composition and biological properties of the hydroalcoholic extract from aerial bulbils were investigated. Complementary information on metabolite composition were obtained using both NMR based untargeted and HPLC-DAD targeted methodologies. The NMR analysis revealed the presence of sugars, organic acids, amino acids, organosulphur compounds (methiin, alliin, allicin and cycloalliin), and other secondary metabolites. In particular, methiin and alliin were identified for the first time in the NMR spectra of aerial bulbil garlic extracts. Polyphenol content was determined by HPLC-DAD analysis: catechin, chlorogenic acid, and gallic acid turned out to be the most abundant phenolics. Hydroalcoholic extract blocked cell proliferation of colon cancer cell line HCT116 with an IC50 of 352.07 µg/mL, while it was non-toxic to myoblast cell line C2C12. In addition, it caused seedling germination reduction of two edible and herbaceous dicotyledon species, namely Cichorium intybus and C. endivia. Moreover, the same extract reduced the gene expression of TNF-α (tumor necrosis factor), HIF1-α (hypoxia-inducible factor), VEGFA (vascular endothelial growth factor), and transient receptor potential (TRP) M8 (TRPM8) indicating the ability to contrast cancer development through the angiogenic pathway. Final, in silico experiments were also carried out supporting the biological effects of organosulphur compounds, particularly alliin, which may directly interact with TRPM8. The results here reported suggest the potential use of garlic aerial bulbils often considered a waste product as a source in phytotherapeutic remedies.

Exploring the link between sulphur-containing compounds and noxious odours at waste management facilities: implications for odour monitoring and mitigation strategies.

With this study we challenge the widely held assumption that sulphur-containing compounds in ambient air are good indicators of the presence noxious odours near waste management facilities. We analysed an extensive set of olfactometric data and data on the concentrations of hydrogen sulphide and trace sulphur compounds (TSCs) near a waste management facility in Croatia in 2021. The results show that the presence of noxious odours significantly correlates only with the concentrations of hydrogen sulphide and methyl mercaptan in ambient air but not with other measured TSCs. Thus, in addition to the measurement of pollutants in ambient air, Integrated Pollution and Prevention Control (IPPC) permits should mandate olfactometric measurements to detect and mitigate noxious odours near waste management facilities.

Effect of Yogurt and Its Components on the Deodorization of Raw and Fried Garlic Volatiles.

Garlic contains sulfur volatiles that cause a bad odor after consumption. The objective of this study was to understand how yogurt and its components cause deodorization. Raw and fried garlic samples were mixed with various treatments and measurements of volatiles were conducted using a selected-ion flow-tube mass spectrometer. Frying garlic significantly reduced almost all sulfur volatile compounds. Raw garlic was deodorized more than fried garlic by all of the treatments. Fat, protein and water significantly reduced the concentration of sulfur-based volatiles in garlic. At the same concentration, either fat or protein produced higher deodorization, depending on the hydrophobicity of the volatile. Whey protein, casein and their complex all caused deodorization. Increasing the pH to 7 or heating changed the structure of the proteins and decreased the deodorization of the volatiles, showing the importance of proteins for deodorization. As the quantity of fat increased, the deodorization of the volatiles also increased. Foods with higher fat or protein content can be formulated to offer a potential solution to reduce the unpleasant odor associated with garlic consumption.

Novel Cytotoxic Sesquiterpene Coumarin Ethers and Sulfur-Containing Compounds from the Roots of Ferula turcica.

Six new sesquiterpene coumarin ethers, namely turcicanol A (1), turcicanol A acetate (2), turcicanol B (3), turcica ketone (4), 11'-dehydrokaratavicinol (5), and galbanaldehyde (6), and one new sulfur-containing compound, namely turcicasulphide (7), along with thirty-two known secondary metabolites were isolated from the root of the endemic species Ferula turcica Akalin, Miski, & Tuncay through a bioassay-guided isolation approach. The structures of the new compounds were elucidated by spectroscopic analysis and comparison with the literature. Cell growth inhibition of colon cancer cell lines (COLO205 and HCT116) and kidney cancer cell lines (UO31 and A498) was used to guide isolation. Seventeen of the compounds showed significant activity against the cell lines.

Multi-dimension analysis of volatile sulfur compound emissions from an urban wastewater treatment plant.

Long-term monitoring of volatile sulfur compounds (VSCs) released at the water-air interface from different treatment units of an anaerobic/oxic (A/O) wastewater treatment plant (WWTP) was carried out to assess the temporal and spatial emission characteristics of VSCs, to explore relationships between wastewater quality and VSC release. The VSC from non-aerated and aerated units were collected using dynamic and static chambers, respectively, and determined using gas chromatography. The VSC emission fluxes diminished in the order of primary sedimentation tank (PST) > anaerobic areas (ANA) > oxic section 1 (OX1). VSCs were not detected in the oxic section 2 (OX2), the oxic areas section 3 (OX3), and the final setting basin (FSB). Release capacities of VSCs descended in the order of summer > fall > spring > winter, with July, August, and September being the months with the highest VSC release capacities. VSC emission fluxes correlated well with wastewater temperatures, sulfate concentrations, and COD. VSC emission flux empirical equations based on wastewater temperature, sulfate concentrations, and COD were established. Based on the established VSC emission empirical equation, a control strategy to reduce the operating costs of deodorization facilities was proposed. This strategy is economically efficient and reduces the consumption of electrical energy.

New Insights on the Scalping Phenomenon of Volatile Sulphur Compounds on Micro-Agglomerated Wine Closures.

Flavour scalping in wine is a well-known phenomenon that is defined as the sorption of flavour compounds on wine closures. While the impact of closure type was the object of several studies, no research has addressed the impact of wine closure permeability on flavour scalping. For that purpose, the adsorption of volatile sulphur compounds (VSCs) on four micro-agglomerated wine cork closures was investigated by soaking them in model and Shiraz wines for 7 days. From a kinetic point of view, most of the VSCs were quickly scalped after 1 h of soaking, and this effect increased after 6 h until reaching a plateau. Most importantly, no significant impact of the closure on the kinetics and adsorption rates of the VSCs was found. As to the quantitative aspects, VSC sorption on closures accounted for 1% to 5% of the initial VSCs present in the wines only, meaning that the impact was negligible under oenological conditions.

Portable chemical detection platform for on-site monitoring of odorant levels in natural gas.

The adequate odorization of natural gas is critical to identify gas leaks and to reduce accidents. To ensure odorization, natural gas utility companies collect samples to be processed at core facilities or a trained human technician smells a diluted natural gas sample. In this work, we report a detection platform that addresses the lack of mobile solutions capable of providing quantitative analysis of mercaptans, a class of compounds used to odorize natural gas. Detailed description of the platform hardware and software components is provided. Designed to be portable, the platform hardware facilitates extraction of mercaptans from natural gas, separation of individual mercaptan species, and quantification of odorant concentration, with results reported at point-of-sampling. The software was developed to accommodate skilled users as well as minimally trained operators. Detection and quantification of six commonly used mercaptan compounds (ethyl mercaptan, dimethyl sulfide, n-propylmercaptan, isopropyl mercaptan, tert­butyl mercaptan, and tetrahydrothiophene) at typical odorizing concentrations of 0.1-5 ppm was performed using the device. We demonstrate the potential of this technology to ensure natural gas odorizing concentrations throughout distribution systems.

Covalent Adduct Formation between ß-Lactoglobulin and Flavor Compounds under Thermal Treatments That Mimic Food Pasteurization or Sterilization.

Thermal processing (e.g., pasteurization and sterilization) is a critical step ensuring the microbial safety of our foods. Previous work from our laboratory has examined the covalent reactions occurring between proteins and a broad selection of flavor compounds under ambient storage temperatures (25-45 °C). However, similar research on reactions of flavor compounds with a protein under thermal processing conditions has not been investigated. In the current study, covalent adduct formation between ß-lactoglobulin (BLG) and 46 flavor compounds encompassing 13 different classes of functional groups was investigated under pasteurization and sterilization conditions by UPLC-ESI-QTOF-MS. BLG was chosen as a representative protein for this study because it is structurally well characterized, its molecular weight is well suited for ESI-MS analysis (18.2 kDa), and it is broadly used in the food industry. Schiff base, aza-Michael addition, and disulfide linkages were the main types of covalent interactions occurring across the reactive samples. Among them, isothiocyanates, aldehydes, and thiol-containing compounds were generally very reactive. Increasing the severity of the thermal treatment [high-temperature-short-time (HTST) pasteurization, in-container pasteurization (IC), and ultra-high-temperature (UHT) sterilization conditions] accelerated the reactions of BLG with flavor compounds, which revealed reactivity of three flavor compounds not previously observed to react at room temperature (eugenol, 4-vinyl phenol, and 3-nonen-2-one). Ketones [other than 2-hydroxy-3-methyl-2-cyclopenten-1-one (cyclotene), diketones, and unsaturated ketones], alcohols, acids, alkenes (terpenes), esters, lactones, 3-acetylpyridine, methyl anthranilate, vanillin, 2-methylthiophene, and dimethyl sulfone did not show measurable reactivity with BLG under the thermal processing conditions examined. An overall view of the data shows that the HTST heat treatment (72 °C for 15 s) had the least effect on the extent of reaction while in-container pasteurization conditions (63 °C for 30 min) produced a similar extent of reaction as the UHT (130 °C 30 s) heat treatment. These varying extents of adductation are in reasonable accord with what one might expect, given that the rates of most classes of chemical reactions occurring near ambient temperature increase by a factor of 2-4 for each increase of 10 K in temperature. Unfortunately, our methodology did not permit us to obtain meaningful data using the most aggressive standard sterilization thermal conditions (110 °C for 30 min) because extensive aggregation/coagulation removed essentially all of the BLG protein from the reaction mixtures prior to MS analysis.

Aroma Characterization of Roasted Meat and Meat Substitutes Using Gas Chromatography-Mass Spectrometry with Simultaneous Selective Detection and a Dedicated Software Tool, AromaMS.

The development of healthier and more sustainable food products, such as plant-based meat substitutes (PBMSs), have received significant interest in recent years. A thorough understanding of the aroma composition can support efforts to improve the sensory properties of PBMS products and promote their consumer acceptability. Here, we developed an integrated hardware and software approach for aroma analysis of roasted food based on simultaneous analysis with three complementary detectors. Following the standard procedure of aroma headspace sampling and separation using solid-phase microextraction-gas chromatography, the column flow was split into three channels for the following detectors for the selective detection of nitrogen and sulfur (N/S)-containing compounds: an electron ionization-mass spectrometry for identification through a library search, a nitrogen-phosphorous detector, and a flame-photometric detector (FPD)/pulsed-FPD. Integration of results from the different types of detectors was achieved using a software tool, called AromaMS, developed in-house for data processing. As stipulated by the user, AromaMS performed either non-targeted screening for all volatile organic compounds (VOCs) or selective screening for N/S-containing VOCs that play a major role in the aroma experience. User-defined parameters for library matching and the retention index were applied to further eliminate false identifications. This new approach was successfully applied for comparative analysis of roasted meat and PBMS samples.

Effect of DAP and glutamine supplementation on sulfur-containing volatiles and sensory properties of Chardonnay wine fermented with Saccharomyces cerevisiae yeast.

Volatile compounds in wine have a critical impact on the consumers' senses. In this study, the effect of diammonium phosphate (DAP) and glutamine on sulfur-containing volatiles and sensory properties of Chardonnay wine fermented with Saccharomyces cerevisiae yeast were evaluated. Fermentation kinetics was determined by monitoring reducing sugar consumption rates during fermentation. The volatile profile of wines was analyzed by headspace solid phase microextraction (HS-SPME) coupled with gas-chromatography-mass spectrometry (GC-MS). The volatile sulfur compounds (VSCs) were analyzed by HS-SPME-GC-MS/MS. Flavor attributes of wines were assessed by a sensory panel with quantitative descriptive analysis. A total of 53 volatiles, including 6 VSCs, were identified and quantified in the Chardonnay wine. The results suggested that glutamine supplementation at the beginning of fermentation could help to initiate fermentation earlier and promote the formation of isoamyl acetate, phenethyl acetate, ethyl nonanoate, methyl decanoate, diethyl succinate and phenethyl alcohol, isobutanol, while DAP supplementation had no obvious effect on the volatile composition of the resulting wine and fermentation kinetics. PRACTICAL APPLICATION: Suitable nitrogen source is helpful to a healthy fermentation, and can also prevent the off-flavor and regulate aroma profile of wine. This study provides insights on the volatile and sensory characteristics of Chardonnay wines affected by different nitrogen source addition.

Biochemical Composition, Antioxidant Activity and Antiproliferative Effects of Different Processed Garlic Products.

Garlic (Allium sativum L.) is a type of agricultural product that is widely used as a food spice, herb and traditional medicine. White garlic (WG) can be processed into several kinds of products, such as green garlic (GG), Laba garlic (LAG) and black garlic (BG), which have multiple health effects. In this study, GC-MS (gas chromatography-mass spectrometry), DPPH (1,1'-diphenyl-2-propionyl hydrazide) radical scavenging, hydroxyl radical scavenging and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) in vitro assays were used to compare the composition, antioxidant and antiproliferation effects of different processed garlic extracts. The relationship between the constituents and the bioactivities was analyzed using the principal components analysis (PCA) and heatmap analysis. BG showed the highest antioxidant activity (IC50 = 0.63 ± 0.02 mg/mL) in DPPH radical assays and the highest antioxidant activity (IC50 = 0.80 ± 0.01 mg/mL) by hydroxyl radical assay. Moreover, GC-MS results showed that 12 organosulfur compounds were detected in the extracts of four garlic products, and allyl methyl trisulfide showed a positive relation with the anticancer activity on SMMC-7721 cells (hepatocellular carcinoma cells). The results suggested that the processing of garlic had a significant influence on the constituents and antioxidant effects and that GG, LAG and BG might be better candidates for the related functional food products compared to WG.

Regenerative one-stage catalytic absorption process with cupric ions for removal of reduced sulfur compounds in polluted air.

Reduced volatile sulfur compounds emitted from e.g. livestock production and biogas production facilities contribute to general air pollution and local odour nuisance. Improved technologies are required to mitigate the emissions of both hydrogen sulfide and organic sulfur compounds. The present study examines the oxidative absorption of reduced sulfur compounds, i.e. hydrogen sulfide, methanethiol and dimethyl sulfide in a wet oxidation process with cupric chloride. It was found that this process efficiently removes both hydrogen sulfide and methanethiol with removal efficiencies >94% under all process conditions tested, while the removal of dimethyl sulfide was in the range 20-40%. The main products determined were dimethyl disulfide, dimethyl trisulfide and elemental sulfur. It was shown that the process was more efficient than the similar process with ferric ions and higher removal could be obtained with lower residence times. Furthermore, though employing cupric ion as metal catalysts results in the production of gaseous sulfur compounds, it is estimated that this process is efficient for deodorization due to the higher odour threshold values of the product compounds and the pH range is optimal for gas streams containing CO2.

Interactions between kafirin and pickle-like odorants in soy sauce flavor Baijiu: Aroma profile change and binding mechanism.

The pickle-like odor, which was caused by the excess volatile sulfur compounds (VSCs), is an undesirable odor in soy sauce flavor Baijiu (SSB). The aim of this study was to explore the suppressing effect of kafirin, the internal prolamin of the raw material of Baijiu, on the pickle-like odor of SSB. The instrumental analysis (comprehensive two-dimensional gas chromatography, ultraviolet and visible spectrophotometry), human perceptions (aroma profile, odor thresholds) and in silico analysis methods (molecular docking) were combined to detect the changes of the pickle-like odor. After the addition of kafirin, the aroma profile of the pickle-like SSB changed and approached to that of the normal SSB. The volatility and the odor thresholds of VSCs decreased 22.05%-64.28% and increased 87.29%-232.57%, respectively. In conclusion, kafirin exhibited a significant suppressing effect on the pickle-like off-odor of SSB, and this effect could be used to reduce the off-odor of SSB and SSB-derived alcoholic beverages.

Effect of face masks on salivary parameters and halitosis: Randomized controlled crossover trial.

BACKGROUND: Face masking is associated with self-perceived dry mouth and halitosis. Aim of the study was to measure the effect of different face masks on salivary parameters and halitosis. METHODS: The randomized controlled crossover clinical trial with four periods included 40 oral healthy participants using different face masks (cloth mask, surgical mask, filtering facepiece 2 [FFP2] mask) or no mask (control) for 4 h in random order. Unstimulated salivary flow rate (primary outcome) and stimulated salivary flow rate, salivary pH and buffer capacity of stimulated and unstimulated saliva (secondary outcomes, blinded), and volatile sulfur compounds (secondary outcome) were measured before and after the 4-h periods. Statistical analysis was performed by repeated measures ANOVA (p < 0.05). RESULTS: Of 40 randomized participants, 39 completed the study. Unstimulated salivary flow rate prior to face masking amounted to 0.6 ± 0.3 ml/min. Face masking had no significant effect on unstimulated salivary flow (p = 0.550). Face masking had also no significant effect on the other salivary parameters (p ≥ 0.518). The concentration of volatile sulfur compounds (VSC) prior to face masking amounted to 157.3 ± 59.7 ppb. After face masking, the concentration of VSC increased slightly, but not significantly (p = 0.055): 168.1 ± 76.3 ppb (control), 199.3 ± 132.7 ppb (cloth masks), 188.5 ± 101.1 ppb (surgical masks), and 189.7 ± 90.1 ppb (FFP2 masks). CONCLUSION: Four hours of face masking did not change the salivary flow rate, pH, and buffer capacity, and had no significant effect on VSC's levels. Wearing face masks does not seem to result in measurable side-effects on salivary parameters such as a reduced salivary flow rate or VSC's levels. CLINICAL TRIAL REGISTRATION: The protocol was prospectively registered at ClinicalTrials.gov (NCT04914208) on June 4, 2021.

Odour impact assessment using kinetics and optimization: case studies on removal of multiple volatile organo-sulphur compounds from sewage wastewater using porous functional materials.

Expanding industries and booming population have led to the increase in the installation of wastewater and sewer systems, even in close proximity to residential areas. Emissions from these installations particularly volatile organo-sulphur compounds (VOSCs) such as methyl mercaptan (CH3SH), ethyl mercaptan (C2H5SH), dimethyl sulphide (CH3SCH3) and carbon disulphide (CS2) are a nuisance to people even when present in small concentration. Strategies for removal involve addition of chemicals or other chemical processes which are generally expensive. Biofilters, on the other hand, consume large amount of energy and wash waters. Hence keeping commercialization in mind, it is important to develop a strategy which would be cost-effective and at the same time be effective to remove most of the odorous compounds present in these systems. In the present research work, granular activated carbons (GAC) are functionalized with alkali solution to improve the adsorption capacity. Liquid phase batch adsorption is performed with GAC and various functionalized activated carbons (FACs) with the help of raw sewage water from a local sewage water treatment plant. Concentration of odour was evaluated by two methods-olfactometry-based analysis for sensory measurement and GCMS-based analysis for analytical estimation of a specific odorous compound. The adsorption capacities of the functionalized GACs are higher primarily because of complex formation at the surface of modified GACs. Pseudo-second-order kinetic model agreed well with experimental results with the rate constant being 0.0191 mg/l min and 0.0153 mg/l min for methyl and ethyl mercaptan adsorption onto FAC-NH3. Boyd's film diffusion along with rate kinetic model supported that chemical adsorption forms the rate-limiting step. Response surface methodology (RSM) was used to optimize the removal of VOSCs with respect to different process parameters like adsorbent amount and time. The olfactometry removal of overall odour was also optimized taking 6 factors in the Box Behnken design. Variance of analysis results indicated that all the models displayed considerable goodness of fit with R2 values close to 1. Methyl mercaptan turned out to be the highest contributor to the overall odour as confirmed both from experimental and optimization study. The optimized olfactometry odour removal (77.4%) along with CH3SH removal (80.34%), C2H5SH removal (59.16%), CH3SCH3 removal (63.21%) and CS2 removal (71.95%) was found at optimum process conditions, with amount of adsorbent of 10.29 g, adsorption time of 2.92 h. This result indicates that methyl mercaptan (CH3SH) is the highest odour contributing component out of the studied VOSCs. The results show promising potential for the use of activated carbon as an adsorbent for removal of odorous compounds from STPs.

Causality Verification for the Correlation between the Presence of Nonstarter Bacteria and Flavor Characteristics in Soft-Type Ripened Cheeses.

Flavor characteristics of ripened cheese are established by various bacteria, such as lactic acid bacteria, Actinobacteria, and Proteobacteria, which spontaneously develop during the cheese-manufacturing process. We previously revealed the relationship between bacterial microbiota and flavor components in soft-type ripened cheeses by using a multiomics approach that combined metagenomics and metabolomics; however, we could not establish a causal relationship. This study aimed to substantiate the causal nature of the correlations revealed by the multiomics approach by using cheese-ripening tests with single isolate inoculation. The bacterial diversity and composition in surface mold-ripened cheeses from Japan and France varied, depending on the differences between the milks (pasteurized or raw), cheese positions (core or rind), and manufacturers. Although the volatile compounds did not clearly reflect the distinctive characteristics of the cheese samples, nonstarter lactic acid bacteria, Actinobacteria, and Proteobacteria positively correlated with ketones and sulfur compounds, as evidenced by a Spearman's correlation analysis. Cheese-ripening tests conducted after inoculation with single bacterial strains belonging to the above-mentioned taxa confirmed that these bacteria formed volatile compounds, in agreement with the correlations observed. In particular, various flavor compounds, such as acids, esters, ketones, and sulfur compounds, were detected in cheese inoculated with Pseudoalteromonas sp. TS-4-4 strain. These findings provide important insights into the role of nonstarter bacteria in the development of cheese flavor and into the effectiveness of the multiomics approach in screening for bacteria that can improve the quality of cheese products. IMPORTANCE Our previous study revealed that the existence of various bacteria, such as lactic acid bacteria, Actinobacteria, and Proteobacteria, clearly correlated with the abundance of flavor components, such as volatile compounds, in soft-type ripened cheeses via a multiomics approach that used 16S rRNA gene amplicon sequencing and headspace gas chromatography-mass spectrometry. However, this approach only showed correlations derived from statistical analyses rather than causal relationships. Therefore, in the present study, we performed cheese-ripening tests using nonstarter bacteria to substantiate the correlations revealed by the multiomics approach in soft-type ripened cheese. Our results suggest the capability of nonstarter bacteria, such as Proteobacteria, to impart flavor to cheese and the effectiveness of the multiomics approach in screening for microbial isolates that can improve the quality of cheese. Overall, our research provides new insights into the importance of bacteria in cheese production.