Enhancing Odor Analysis with Gas Chromatography-Olfactometry (GC-O): Recent Breakthroughs and Challenges.

Gas chromatography-olfactometry (GC-O) has made significant advancements in recent years, with breakthroughs in its applications and the identification of its limitations. This technology is widely used for analyzing complex odor patterns. The review begins by explaining the principles of GC-O, including sample preparation, separation methods, and olfactory evaluation techniques. It then explores the diverse range of applications where GC-O has found success, such as food and beverage industries, environmental monitoring, perfume and aroma development, and forensic analysis. One of the major breakthroughs in GC-O analysis is the improvement in separation power and resolution of odorants. Techniques like rapid GC, comprehensive two-dimensional GC, and multidimensional GC have enhanced the identification and quantification of odor-active chemicals. However, GC-O also has limitations. These include the challenges in detecting and quantifying trace odorants, dealing with matrix effects, and ensuring the repeatability and consistency of results across laboratories. The review examines these limitations closely and discusses potential solutions and future directions for improvement in GC-O analysis. Overall, this review presents a comprehensive overview of the recent advances in GC-O, covering breakthroughs, applications, and limitations. It aims to promote the wider usage of GC-O analysis in odor analysis and related industries. Researchers, practitioners, and anyone interested in leveraging the capabilities of GC-O in analyzing complex odor patterns will find this review a valuable resource. The article highlights the potential of GC-O and encourages further research and development in the field.

The potential use of Indian rice flour or husk in fortification of pan bread: assessing bread's quality using sensory, physicochemical, and chemometric methods.

Hassawi rice is an Indica variety cultivated in Saudi Arabia with a higher nutritional value than the commercial Basmati rice varieties. The present study has investigated the feasibility of combining Hassawi rice flour (HRF) or husk (HRHF), an abundant byproduct, with wheat flour to produce nutritious economical pan bread. To achieve this aim, the physicochemical properties of HRF and HRHF were assessed using techniques such as UPLC-tandem MS, ICP-OES, and colorimeter. The proximate composition (moisture, crude fiber, and ash) and mineral contents of HRHF are significantly (p < 0.05) higher than HRF. On the other hand, the compounds p-coumaric acid, vanillic acid, γ- and δ-tocotrienols, and γ-oryzanol were unique to HRF. We further determined the changes in sensory, technological, and physicochemical properties of wheat flour bread substituted with 5%, 10%, and 15% of HRF or HRHF. The rheological tests showed that the addition of HRF and HRHF increased dough development and stability time. Further, substituting wheat flour for HRF and HRHF at levels higher than 10% affected sensory attributes, such as color, taste, odor, flavor, and appearance. These changes, however, were not always at a significant level. The causes of the differences in properties between control and fortified bread samples were investigated by chemometric methods. Samples of bread +HRF at 5 and 10% had comparable overall profiles to the control. On the other hand, bread +HRHF samples proved to retain higher concentrations of bioactive molecules compared to the control bread. Our findings shed light on the possible use of rice husk fibers in baking goods, notably pan bread. Furthermore, by integrating rice husk fibers into baked goods, we may boost their health benefits while also contributing to the long-term use of agricultural waste.

The Bioactive Substances in Spent Black Tea and Arabic Coffee Could Improve the Nutritional Value and Extend the Shelf Life of Sponge Cake after Fortification.

The study aimed to evaluate the potential use of spent coffee powder (SCP) and spent tea powder (STP) as bioactive supplements for sponge cake. To achieve this aim, we initially compared the chemical properties of spent tea and coffee powders with those of their raw forms. Subsequently, three supplemented cake blends were prepared (1, 2, and 3% of SCP and STP) to test the effect of their addition on the chemophysical characteristics, sensory attributes, and shelf life of the final products. Our results indicated that spent tea and coffee are prospective materials for polyphenols. Spent tea powder could retain up to 72% (theaflavin trigallate), while spent coffee powder could retain up to 63.9% (1-caffeoylquinic acid) of the identified compounds compared to the raw materials. Furthermore, spent tea and coffee powders contained high levels of dietary fiber (18.95 and 31.65 g/100 g dry weight) and the elements potassium (254.6 and 1218.2 mg/100 g of DW), phosphorus (189.8 and 161.3 mg/100 g of DW), calcium (904.1 and 237.8 mg/100 g of DW), and magnesium (158.8 and 199.6 mg/100 g of DW). In addition, the fortified samples with SCP and STP significantly enhanced the nutritional values while retaining good sensory qualities compared to those of the control sample. Moreover, cakes fortified with the highest concentrations of SCP and STP (3%) showed a significant decrease in malondialdehyde content (MDA; 17.7 and 18.0 µg/g) and microbiological counts (2.4 and 2.5 log cfu/g) compared to the control cake after 14 days of storage. These findings suggest that incorporating SCP and STP into cakes not only enhances their nutritional value but also extends their shelf life. By utilizing these waste products, we can contribute to a more sustainable and ecofriendly food industry.

CMTM6 shapes antitumor T cell response through modulating protein expression of CD58 and PD-L1.

The dysregulated expression of immune checkpoint molecules enables cancer cells to evade immune destruction. While blockade of inhibitory immune checkpoints like PD-L1 forms the basis of current cancer immunotherapies, a deficiency in costimulatory signals can render these therapies futile. CD58, a costimulatory ligand, plays a crucial role in antitumor immune responses, but the mechanisms controlling its expression remain unclear. Using two systematic approaches, we reveal that CMTM6 positively regulates CD58 expression. Notably, CMTM6 interacts with both CD58 and PD-L1, maintaining the expression of these two immune checkpoint ligands with opposing functions. Functionally, the presence of CMTM6 and CD58 on tumor cells significantly affects T cell-tumor interactions and response to PD-L1-PD-1 blockade. Collectively, these findings provide fundamental insights into CD58 regulation, uncover a shared regulator of stimulatory and inhibitory immune checkpoints, and highlight the importance of tumor-intrinsic CMTM6 and CD58 expression in antitumor immune responses.

The Chemical, Rheological, and Sensorial Characteristics of Arabic Bread Prepared from Wheat-Orange Sweet Potatoes Flour or Peel.

The current study investigates the feasibility of preparing Arabic bread from wheat flour, sweet potato flour, or peeled sweet potatoes based on the nutritional values, technological characteristics, and sensory properties of the final products. First, we analyzed the proximate, elemental, total and individual phytochemical compositions of the raw materials and bread samples. The analysis showed that potassium, calcium, and phosphorus were higher in peels than pulp, in the same manner to the total phenolics, flavonoids, and anti-radical scavenging activities. Phenolic acids and flavonols were quantified, where p-coumaric, feruloyl-D-glucose, eucomic, gallic, and ferulic acids were measured as major phenolic acids in either peels or pulp flours, and their quantities were higher in the peels. Furthermore, we evaluated the effects of wheat substitution on the properties of the dough blends and their final bakery. The results indicated that the fortified samples' nutritional and rheological properties were significantly improved, while their sensory qualities were comparable to those of the control. Thereby, the fortified dough blends presented higher dough stabilities, indicating a wider range of applications. Additionally, after the heat treatment, the fortified breads maintained significantly higher total phenolic, flavonoid, anthocyanin, and carotenoid contents, and total antioxidant activities, implying their accessibility for humans upon consumption.

Comparative Evaluation of Wild and Farmed Rainbow Trout Fish Based on Representative Chemosensory and Microbial Indicators of Their Habitats.

Wild and farmed rainbow trout were compared with chemical profiling, chemosensory properties, carbon concentration and isotope analyses, 1- and 2-GC/O-MS, GC-FID, and aroma profile analyses. Results were linked with the prokaryotic and eukaryotic microbiological profile of the fish sources using multivariate statistical analysis. Fish from natural environments proved to have better sensory properties in terms of fruity, sweet, and citrusy attributes, compared to farmed fish. However, the farmed fish were found to have higher nutritional value based on their lipid contents. These differences might relate to the introduction of feed extrudates, which could influence the overall quality of fish products. Thereby, malodor episodes linked to musty/earthy off-odor notes related to odorants including geosmin, ß-caryophyllene, (E,Z)-2,4-nonadienal, and (E,E)-2,4-nonadienal. These compounds, in turn, correlated with Asticcacaulis benevestitus, Curvibacter sp., Albidiferax sp., Aquabacterium commune, and Aquabacterium citratiphilum abundance and were further affected by oxygen levels in the water column.

SHP-2 and PD-1-SHP-2 signaling regulate myeloid cell differentiation and antitumor responses.

The inhibitory receptor PD-1 suppresses T cell activation by recruiting the phosphatase SHP-2. However, mice with a T-cell-specific deletion of SHP-2 do not have improved antitumor immunity. Here we showed that mice with conditional targeting of SHP-2 in myeloid cells, but not in T cells, had diminished tumor growth. RNA sequencing (RNA-seq) followed by gene set enrichment analysis indicated the presence of polymorphonuclear myeloid-derived suppressor cells and tumor-associated macrophages (TAMs) with enriched gene expression profiles of enhanced differentiation, activation and expression of immunostimulatory molecules. In mice with conditional targeting of PD-1 in myeloid cells, which also displayed diminished tumor growth, TAMs had gene expression profiles enriched for myeloid differentiation, activation and leukocyte-mediated immunity displaying >50% overlap with enriched profiles of SHP-2-deficient TAMs. In bone marrow, GM-CSF induced the phosphorylation of PD-1 and recruitment of PD-1-SHP-2 to the GM-CSF receptor. Deletion of SHP-2 or PD-1 enhanced GM-CSF-mediated phosphorylation of the transcription factors HOXA10 and IRF8, which regulate myeloid differentiation and monocytic-moDC lineage commitment, respectively. Thus, SHP-2 and PD-1-SHP-2 signaling restrained myelocyte differentiation resulting in a myeloid landscape that suppressed antitumor immunity.

Antigen presentation safeguards the integrity of the hematopoietic stem cell pool.

Hematopoietic stem and progenitor cells (HSPCs) are responsible for the production of blood and immune cells. Throughout life, HSPCs acquire oncogenic aberrations that can cause hematological cancers. Although molecular programs maintaining stem cell integrity have been identified, safety mechanisms eliminating malignant HSPCs from the stem cell pool remain poorly characterized. Here, we show that HSPCs constitutively present antigens via major histocompatibility complex class II. The presentation of immunogenic antigens, as occurring during malignant transformation, triggers bidirectional interactions between HSPCs and antigen-specific CD4+ T cells, causing stem cell proliferation, differentiation, and specific exhaustion of aberrant HSPCs. This immunosurveillance mechanism effectively eliminates transformed HSPCs from the hematopoietic system, thereby preventing leukemia onset. Together, our data reveal a bidirectional interaction between HSPCs and CD4+ T cells, demonstrating that HSPCs are not only passive receivers of immunological signals but also actively engage in adaptive immune responses to safeguard the integrity of the stem cell pool.

Chemo-sensory characterization of aroma active compounds of native oak wood in relation to their geographical origins.

Oak wood contains aroma-active compounds that contribute significantly to the chemical structure, olfactory and gustatory qualities of alcoholic beverages and vinegars as by-products that have been either fermented and/or aged in oak barrels. The chemical composition of cooperage oak is highly variable, depending on the degree of toasting and natural seasoning. However, it is unclear whether the odor of oak varies according to different geographical regions and pedoclimatic conditions. Especially in view of the actual challenges in forestry in relation to climate change, the present study aimed at elucidating the odorous constituents of nine natural oak samples from Germany, Austria and Hungary with respect to these influencing parameters. The odor profiles of the oaks were compared, the potent odorants were determined, and selected odorants were quantified using stable isotope dilution assays (SIDA). The majority of the identified odorants in all samples were fatty acid degradation products, followed by a series of odorants with terpenoic structure and others resulting from the degradation of lignin. Several different odorants including 2-propenoic acid and cinnamaldehyde are reported here for the first time in oaks from different growth regions. Odor activity values (OAVs), calculated based on odor thresholds (OTs) in water, revealed hexanal, (E)-2-nonenal, (Z)-3-hexenal, eugenol, vanillin, and whiskey lactone as potent odorants for the oak odor. Principal component analysis of the data obtained from sensory evaluation, comparative aroma extract dilution analysis (cAEDA) and their corresponding quantified odorants showed that the highest separation rate was obtained for Hungarian oak, whereas Austrian and Bavarian oak samples were more similar. Recombination experiments by mixing the dominant odorants in their naturally occurring concentrations revealed a good agreement of the smell properties of the model mixture with the smell of the respective original sample. These findings aimat evaluating and establishing a better understanding of the distinctive smell of oak wood and demonstrated the prospects of new oak sources.

Metabarcoding profiling of microbial diversity associated with trout fish farming.

Earthy and musty off-flavors are routinely observed in farmed trout worldwide. The microbial association to the production of those off-flavors was previously reported. The current manuscript aimed to catalog the microbial enrichment (eukaryotes and prokaryotes) in semi-intensive aquaculture freshwater sources that might influence the trout aquaculture quality production. The 16S rRNA and ITS metabarcoding analyses were applied on the inflow- and pond-water samples from trout farms previously recorded a malodor fish products and located alongside Moosach and Sempt Rivers in Bavaria province, Germany. The results showed that more than 99% of the detected prokaryotic OTUs (Operational Taxonomic Unit identification) were bacteria as of ~ 75.57% were Proteobacteria, and ~ 14.4% were Bacteroidetes. Meanwhile, 118 out of 233 of the eukaryotic OTUs were known species. Of these, ~ 45% were plant pathogens, and ~ 28% were mushroom/yeasts. Based on the comparative analysis between inflow- and pond-water samples, several pro- and eukaryotic microorganisms that affect the trout aquaculture water quality and industry have been detected, including the malodor-producing microorganisms, e.g., Cyanobacteria and Actinobacteria, along with fish infectious microorganisms, e.g., Chilodonella cyprinid, Metschnikowia bicuspidate. Additionally, the effect of the human- and industrial-related activities around the sampling area on the microbiota of the investigated farms were highlighted.

Molecular and sensory characterization of odorants in Cembran pine (Pinus cembra L.) from different geographic regions.

The wood of the Cembran pine (Pinus cembra L.), also known as Swiss pine, Arolla pine or Stone pine, has a prominent and long-lasting odor which has been reported to relieve stress in humans. However, the odorants responsible for this are unknown and it is also unclear whether the odor profile depends on the origin of the trees, namely different geographical regions and pedoclimatic conditions. Therefore, in this study human sensory analyses together with isolation and analysis of the target odorants via solvent-assisted flavor evaporation were performed. Afterwards, comparative odor extract dilution analysis (cOEDA) was applied to investigate the odorous constituents of pinewood samples from forests in Austria and Italy. Specific odorants were thereby identified using one-dimensional and two-dimensional gas chromatography-mass spectrometry/olfactometry using two capillary columns with different polarities (DB-5 and DB-FFAP). In total, 103 odorants were detected with successful identification of 98 of these substances. The identified odorants were predominately monoterpenes and sesquiterpenes as well as organic acids. Several compounds including germacrene D, thymol, carvacrol, rotundone, ß-caryophyllene, α-humulene, cinnamaldehyde, and ethyl cinnamate are reported here for the first time as odorous constituents of pinewood. Principal component analysis of the data obtained from sensory evaluation and cOEDA indicated that terpenes and sesquiterpenes were correlated with higher hedonic rates for the wood samples. Moreover, a Mantel test between the geographical distances of the trees and their sensory and cOEDA values demonstrated that the origin of the trees had a significant impact on the sensory characteristics of the wood, in agreement with the differences in the relative proportions of different volatile components. As such, the odor of Cembran pinewood is prone to variation but, yet, unique.

Targeted deletion of PD-1 in myeloid cells induces antitumor immunity.

PD-1, a T cell checkpoint receptor and target of cancer immunotherapy, is also expressed on myeloid cells. The role of myeloid-specific versus T cell-specific PD-1 ablation on antitumor immunity has remained unclear because most studies have used either PD-1-blocking antibodies or complete PD-1 KO mice. We generated a conditional allele, which allowed myeloid-specific (PD-1f/fLysMcre) or T cell-specific (PD-1f/fCD4cre) targeting of Pdcd1 gene. Compared with T cell-specific PD-1 ablation, myeloid cell-specific PD-1 ablation more effectively decreased tumor growth. We found that granulocyte/macrophage progenitors (GMPs), which accumulate during cancer-driven emergency myelopoiesis and give rise to myeloid-derived suppressor cells (MDSCs), express PD-1. In tumor-bearing PD-1f/fLysMcre but not PD-1f/fCD4cre mice, accumulation of GMP and MDSC was prevented, whereas systemic output of effector myeloid cells was increased. Myeloid cell-specific PD-1 ablation induced an increase of T effector memory cells with improved functionality and mediated antitumor protection despite preserved PD-1 expression in T cells. In PD-1-deficient myeloid progenitors, growth factors driving emergency myelopoiesis induced increased metabolic intermediates of glycolysis, pentose phosphate pathway, and TCA cycle but, most prominently, elevated cholesterol. Because cholesterol is required for differentiation of inflammatory macrophages and DC and promotes antigen-presenting function, our findings indicate that metabolic reprogramming of emergency myelopoiesis and differentiation of effector myeloid cells might be a key mechanism of antitumor immunity mediated by PD-1 blockade.

Odorants in Fish Feeds: A Potential Source of Malodors in Aquaculture.

Although the microbiota is considered to be the primary source of off-flavors in farmed fish, there is a lack of information about the possible contribution of feeds to fish malodor. For this reason, the current study was designed to perform comprehensive sensory and chemo-analytical characterization of fish feed constituents that can impact the quality of farmed fish, and to determine whether feeds cause malodor accumulation in fish. To this aim, odorants in four commercial fish feeds were extracted using solvent assisted flavor evaporation (SAFE) and characterized by comparative aroma extract dilution analysis (cAEDA) and multi-dimensional gas chromatography-mass spectrometry/olfactometry (MD-GC-MS/O). The odorants in the fish feed samples were correlated with their respective sensory and fatty acid profiles. The cAEDA studies revealed the presence of 81 odorants of which 55 compounds were common to all the samples. Most of these odorants are identified here for the first time in fish feeds, and include skatole, indole, (E,Z,Z)-2,4,7-tridecatrienal, 4-ethyloctanoic acid, and cresols. Additionally, geosmin and 3-isopropyl-2-methoxypyrazine, known for their contribution to fish taint, and other cyanobacterial by-products, dimethyldisulfide and dimethyltrisulfide, were identified in feed samples. The results suggest that fish feed may contribute to fish malodor. Most of these off-flavors were linked to lipid source (fish oil or plant/lard alternatives), unsaturated fatty acids contents, and protein type (plant-based or fishmeal-based sources) in the feed.