Search Results (49)

Background: scleroglucan, an extracellular polysaccharide with gel-forming, thickening, and stabilizing properties, was used as a structure-forming agent in low-fat yogurt formulations. The aim of this study was to evaluate its influence on the fermentation process and the physicochemical, rheological, textural, microstructural, and sensory properties of the yogurts. Methods: control samples were formulated with the addition of skim milk powder (SMP), whereas experimental yogurts contained scleroglucan at concentrations of 0.25%, 0.5%, and 1.0% (w/w). The fermentation kinetics, acidity, color, syneresis, rheological behavior, texture profile, microstructure, and volatile compounds were analyzed during storage. Results: the results showed that scleroglucan slowed acidification and increased the apparent viscosity, yield stress, and firmness of yogurts, while completely eliminating syneresis. Scleroglucan also modified the volatile profile by decreasing acetaldehyde and increasing 2,3-pentanedione levels during storage. The survival of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus was not affected. Conclusions: the yogurt containing 1.0% scleroglucan was rated highest in overall acceptability. These findings demonstrate that scleroglucan can serve as a natural, clean-label stabilizer and an alternative to skim milk powder in low-fat set-style yogurts. Full article

The traditional use of iced trash fish (IF) in Chinese mitten crab (Eriocheir sinensis) aquaculture raises sustainability concerns, but the shift to formulated feeds (FF—a commercial compound feed specifically designed to meet nutritional requirements by blending multiple ingredients and containing a balance of nutrients) is often hindered by fears of compromising its prized flavor. This study aimed to comprehensively evaluate whether a commercial formulated feed could effectively replace IF without diminishing flavor quality, hypothesizing that FF would alter the intestinal volatile profile, thereby influencing muscle flavor. Male crabs were fed either IF or FF for eight weeks. Muscle flavor was assessed using sensory evaluation, electronic nose (E-nose), and gas chromatography–ion mobility spectrometry (GC–IMS). Volatile compounds in intestinal chyme were also analyzed by GC–IMS to explore potential transfer mechanisms. The results indicated that crabs fed with FF showed higher sensory scores for sweetness. Additionally, the E-nose analysis revealed a clear separation trend between dietary groups and showed markedly higher sensor response values for aromatic compounds, biogenically derived compounds and Maillard reaction products, sulfur-containing organic compounds, aliphatic hydrocarbons, total volatile organic compounds, alcohols and organic solvents, and alkenes in the FF group compared to the IF group. Thirty-four volatiles were discovered in the muscle. Statistical analysis (independent samples t-test) showed that the FF group exhibited significantly elevated levels of 3-methylbutanal-M, propanal, (E)-2-pentenal, 2,3-pentanedione, and pentan-1-ol-M, whereas the IF group exhibited significantly elevated levels of 2-hexanone, dihydro-2(3H)-furanone, butyl acetate, ethyl 2-methylpropanoate, and phenol (p < 0.05). Fourty-eight volatiles were identified in the intestinal chyme. Propanal and ethyl 2-methylpropanoate were the dominant odor contributors based on correlation network analysis. Strong correlations were identified between the flavor profiles of intestinal chyme and muscle, suggesting a potential transfer or transformation of volatiles. This work provides a scientific basis for optimizing aquafeed formulations to ensure sustainable crab production without sacrificing end-flavor quality. Full article

Chilled yak meat is becoming more and more popular with the improvement in living standards, and the flavor of chilled meat is closely related to storage time. The effect of storage time on the flavor of chilled yak meat was explored in this study. We used GC-MS, HS-GC-IMS, and LC-MS/MS to detect changes in the metabolites in yak meat during storage at 4 °C and constructed storage time-dependent metabolite fingerprints of the yak meat. The results showed that low-temperature storage promoted the degradation of proteins and lipids, nucleotide release, and the production of the volatile compounds heptanal, octanal, n-nonanal, benzaldehyde, 2,3-pentanedione, 3-hydroxy-2-butanone, and 2-butanone. With an increase in the chilled storage time of yak meat, the total volatile basic nitrogen and total viable count of the meat were significantly increased. The short-term storage time of yak meat at 4 °C should not exceed 5 days. Full article

This study aims to investigate the oxidative pyrolysis of biomass volatiles with a particular focus on the formation of liquid products. Furfural, hydroxyacetone, and 3,4-dimethoxybenzaldehyde were chosen as volatile model compounds. The impacts of the oxygen equivalence ratio (ER, 0–15%) and temperature (400–500 °C) on the product composition and distribution were examined using a two-stage quartz-tube reactor. The results showed that volatile pyrolysis was limited at the lower temperature of 400 °C even with oxygen introduction, while it could be significantly promoted at 500 °C as illustrated by the observed great decrease in the GC-MS peak areas of the volatile compounds especially under an oxidative atmosphere. For instance, the peak area of 3,4-dimethoxybenzaldehyde at 500 °C under an ER of 4% was only ~9% of that at 400 °C. Oxygen introduction enhanced the volatile decomposition with the formation of mainly permanent gases (although not given in the study) rather than liquid products, but distinct impacts were obtained for varied volatile compounds possibly due to their different chemical structures and autoignition temperatures. From the perspective of liquid product formation, furfural would undergo the cleavage of C-C/C-O bonds to form linear intermediates and subsequent aromatization to generate aromatics (benzene and benzofuran). The presence of oxygen could enhance the oxidative destruction of the C-C/C-O bonds and the removal of O from the molecules to form simple aromatics such as benzene, phenol, and toluene. Hydroxyacetone mainly underwent C-C/C-O cleavage that was further enhanced in the presence of oxygen; the resultant intermediates would recombine to generate acetoin and 2,3-pentanedione. A higher ER would directly oxidize the alcoholic hydroxyl group (-OH) into an aldehyde group (-CHO) to form methyl glyoxal, while 3,4-dimethoxybenzaldehyde mainly underwent cleavage and recombination of bonds connected with the benzene ring including aldehyde group (-CHO), C_Ar-O, C_Methoxy-O bonds, thus forming 1,2-dimethoxybenzene, toluene, and 3-hydroxybenzadehyde. This study provides more fundamental insights into the homogeneous oxidation of volatiles during the oxidative fast pyrolysis of biomass, facilitating the deployment of this technology. Full article

This study examines the fermentation performance of featured bacteria (Lactobacillus acidophilus-ATCC-4356, Lactobacillus helveticus-ATCC-15009, Lactobacillus delbrueckii subsp. bulgaricus-ATCC-11842, Lacticaseibacillus casei-ATCC-393, Streptococcus thermophilus-ATCC-19258 (ST), and Bifidobacterium bifidum-ATCC-29521 (BB)) used in fermented dairy products and their impact on product quality. The main focus is on evaluating the metabolic activities, organic acid production, viscosity values, and sensory properties of probiotic strains such as L. acidophilus, L. bulgaricus, L. casei, L. helveticus, B. bifidum, and S. thermophilus. The strains were activated in a sterile milk medium and incubated until they reached a pH of 4.6. Then, pH, microbial enumeration, organic acid, sugar composition, vitamins A, D, E, K1, and K2 (menaquinone-7), and viscosity values were measured in the bacteria. Organic acid, sugar composition, and vitamins A, D, E, K1, and K2 (menaquinone-7) were analyzed with the HPLC method. Additionally, sensory analyses were performed, and volatile compounds were examined. L. casei demonstrated superiority in lactic acid production, while L. helveticus showed high lactose consumption. L. bulgaricus stood out in galactose metabolism. The highest viscosity was observed in products produced by B. bifidum. Differences in viscosity were attributed to exopolysaccharide (EPS) production and acid production capacity. A total of 62 volatile compounds were identified, with the highest levels of aromatic components found in products containing B. bifidum. The most preferred product, based on panel evaluations, was the fermented dairy product produced with L. acidophilus. As for aroma profiles, it was determined that the phenethyl alcohol, 3-methyl-1 butanol, and ethanol compounds are associated with B. bifidum, the hexanoic acid and 2-methylbutanal compounds are associated with the L. acidophilus, the hexanoic acid, 2-methylbutanal, 2-furanmethanol, and acetaldehyde compounds are associated with the L. bulgaricus, and the hexanoic acid, 2-methylbutanal, 2-heptanone, acetoin, and d-limonene are associated with the L. casei. On the other hand, the L. helveticus strain is associated with the hexanoic acid, 2-methylbutanal, and 2-heptanone, and the S. termophilus strain is associated with the hexanoic acid, hexanol, acetoin, 2,3-pentanedione, 1-butanol, and 3-methyl-2-butanone volatile aroma compounds. The determination of fat-soluble vitamins is particularly important for vitamin K1 and vitamin K2. In this study, the bacterial sources of these vitamins were compared for the first time. The menaquinone-7 production by L. helveticus was determined to be the highest at 0.048 µg/mL. The unique metabolic capacities of these prominent cultures have been revealed to play an important role in determining the aroma, organic acid content, viscosity, and overall quality of the products as a whole. Therefore, the findings of this study will provide the right strain selection for a fermented dairy product or a different non-dairy-based fermented product according to the desired functional properties. It also provides a preliminary guide for inoculation in the right ratios as an adjunct culture or co-culture for a desired property. Full article

Marselan wine is characterized by distinctive flavors of blackcurrant, cranberry, and spice, which are significantly influenced by environmental factors such as region and climate. In this study, we analyzed the dynamic changes in the microbial community, physicochemical indices, and flavor compounds during the spontaneous fermentation of Marselan wine in Xinjiang using high-throughput sequencing (HTS), high-performance liquid chromatography (HPLC), and headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC-MS). The results indicated that the sugar content decreased from 259.12 g/L to 22.45 g/L, while the ethanol content increased to 13.63 ± 0.15% vol after 12 days of fermentation. The predominant aromatic components identified in Marselan grapes include isophorone, 2,3-pentanedione, 2-hexenal, and melonal. After fermentation, ethanol, phenethyl alcohol, isoamyl acetate, ethyl acetate, and ethyl hexanoate were produced, imparting rose, cream, and fruit flavors to wine. The key microorganisms involved in the spontaneous fermentation of Marselan wine include Saccharomyces, Starmerella, Pichia, Pseudomonas, Sphingomonas, and Aspergillus. These microorganisms contributed substantially to the main physicochemical indices and flavor profiles. Saccharomyces and Pichia enhanced the formation of most alcohols and esters, whereas Aspergillus, Acremonium, and Fusarium inhibited the synthesis of numerous volatile compounds. These findings provide valuable theoretical references for improving the quality of Marselan wines in Xinjiang. Full article

The selective separation of adjacent rare earth elements (REEs), such as La(III) and Ce(III), is a critical challenge in hydrometallurgy due to their similar chemical properties. This work evaluates the performance of non-dispersive solvent extraction (NDSX) using hollow fiber (HF) membranes for this purpose. Initial solvent extraction (SX) equilibrium experiments with Cyanex^® 272 in kerosene determined that the aqueous phase’s optimal pH for selectivity is 5.6, achieving a selectivity of ${\alpha }_{Ce/La}=$12.7. NDSX experiments demonstrated enhanced selectivity ${\alpha }_{Ce/La}=34$ after 120 min, benefiting from the additional mass transfer resistance provided by the HF membrane. Maintaining a constant pH of 5.0 with NaOH improved extraction rates but slightly reduced selectivity to ${\alpha }_{Ce/La}=26$. Experiments using 1,1,1-trifluoro-2,4-pentanedione (HTFAC) in the ionic liquid (IL) [Omim][Tf2n] as the receiving phase showed lower extraction rates but achieved comparable selectivity values (${\alpha }_{Ce/La}=22$) in just 20 min, thanks to the IL’s viscosity limiting La(III) extraction. The impact of HF membrane design was also assessed; increasing the membrane’s surface area significantly improved extraction rates but reduced selectivity due to reduced mass transfer resistance. These results demonstrate the potential of NDSX systems for selective REE separation, particularly by leveraging controlled mass transfer and operating conditions. However, further work is needed to optimize system design. The findings highlight the advantages of NDSX over traditional SX, offering a promising pathway for sustainable and efficient REE processing. Full article

The lactic acid bacteria Streptococcus thermophilus and Lactobacillus helveticus are commonly used as starter cultures in dairy product production. This study aimed to investigate the characteristics of fermented milk using different ratios of these strains and analyze the changes in volatile compounds during fermentation and storage. A 10:1 ratio of Streptococcus thermophilus CICC 6063 to Lactobacillus helveticus CICC 6064 showed optimal fermentation time (4.2 h), viable cell count (9.64 log10 colony-forming units/mL), and sensory evaluation score (79.1 points). In total, 56 volatile compounds were identified and quantified by solid-phase microextraction and gas chromatography–mass spectrometry (SPME-GC-MS), including aldehydes, ketones, acids, alcohols, esters, and others. Among these, according to VIP analysis, 2,3-butanedione, acetoin, 2,3-pentanedione, hexanoic acid, acetic acid, acetaldehyde, and butanoic acid were identified as discriminatory volatile metabolites for distinguishing between different time points. Throughout the fermentation and storage process, the levels of 2,3-pentanedione and acetoin exhibited synergistic dynamics. These findings enhance our understanding of the chemical and molecular characteristics of milk fermented with Streptococcus thermophilus and Lactobacillus helveticus, providing a basis for improving the flavor and odor of dairy products during fermentation and storage. Full article

The molecule (S)-4,5-dihydroxy-2,3-pentanedione (DPD) is produced by many different species of bacteria and is involved in bacterial communication. DPD is the precursor of signal molecule autoinducer-2 (AI-2) and has high potential to be used as a vaccine adjuvant. Vaccine adjuvants are compounds that enhance the stability and immunogenicity of vaccine antigens, modulate efficacy, and increase the immune response to a particular antigen. Previously, the microparticulate form of (S)-DPD was found to have an adjuvant effect with the gonorrhea vaccine. In this study, we evaluated the immunogenicity and adjuvanticity of several synthetic analogs of the (S)-DPD molecule, including ent—DPD((R)-4,5-dihydroxy-2,3-pentanedione), n-butyl—DPD ((S)-1,2-dihydroxy-3,4-octanedione), isobutyl—DPD ((S)-1,2-dihydroxy-6-methyl-3,4-heptanedione), n-hexyl—DPD ((S)-1,2-dihydroxy-3,4-decanedione), and phenyl—DPD ((S)-3,4-dihydroxy-1-phenyl-1,2-butanedione), in microparticulate formulations. The microparticulate formulations of all analogs of (S)-DPD were found to be noncytotoxic toward dendritic cells. Among these analogs, ent—DPD, n-butyl—DPD, and isobutyl—DPD were found to be immunogenic toward antigens and showed adjuvant efficacy with microparticulate gonorrhea vaccines. It was observed that n-hexyl—DPD and phenyl—DPD did not show any adjuvant effect. This study shows that synthetic analogs of (S)-DPD molecules are capable of eliciting adjuvant effects with vaccines. A future in vivo evaluation will further confirm that these analogs are promising vaccine adjuvants. Full article

In the present work, we studied the interaction of polyphenylsilsesquioxane with various β-diketonate complexes of titanium by mechanochemical activation. Polyphenylsilsesquioxane, bis-(2,4-pentanedionate) titanium dichloride, bis-(1-phenyl-1,3-butanedionate) titanium dichloride, and bis-(1,3-diphenyl-1,3-propanedionate) titanium dichloride were used as starting reagents. Various chemical and physicochemical methods of analysis were used to study the synthesis products. The composition of the obtained compounds has been determined. It is shown that under conditions of mechanochemical activation, high-molecular-weight products with a Si/Ti ratio different from the specified ones are formed. In addition, under the action of mechanical stresses, the initial titanium complexes (except for acetylacetonate complex) polymerize with the formation of coordination of high-molecular-weight compounds, which are destroyed by the addition of ethyl alcohol. It has been established that with an increase in the volume of the organic ligand, titanium atoms enter the polymer siloxane chain to a lesser extent. This work is aimed at finding efficient and environmentally friendly methods for the synthesis and modification of organometallic macromolecular compounds. Full article

The banana quality evaluation system is not sufficiently mature in China and cannot meet the demand of producing high-quality processed banana products. In order to screen banana varieties suitable for low-temperature vacuum frying and extend the banana deep processing industry chain, banana slices from 15 varieties planted in China were prepared by low-temperature vacuum-frying (VF) technology in the present study. After factor analysis on 20 indicators of sensory, flavor, nutritional and processing quality from different varieties of banana slices, comprehensive quality evaluation models were constructed for banana slices. It was concluded that Meishijiao No. 1 had the highest overall score among the 15 banana varieties; hence, it was deemed suitable for processing. Meanwhile, in order to investigate the difference between flavor substances in banana slices before and after processing, a flavor histology study was conducted with solid-phase microextraction (SPME) and comprehensive two-dimensional gas chromatography coupled to time-of flight mass spectrometry (GC×GC-TOFMS). It was found that the content differences of 2,3-pentanedione, hexanal and pentanal may cause the weakened fruitiness and the increased oil flavor of banana taste. Full article

Scandium complexes with β-diketonate ligands are valuable precursors for the metal–organic chemical vapor deposition (MOCVD) of scandia based materials, but data on their volatilization thermodynamics crucial to MOCVD technology are in a huge disarray. We have addressed this issue with a diagnostic tool based on the principles of group additivity and structure–property relationships, which had been developed by us specifically for metal–organic objects. For this purpose, a mass of experimental data on the vapor pressures and enthalpies of sublimation, vaporization and fusion available in the literature for scandium(III) β-diketonates has been compiled and analyzed. Additionally, saturated vapor pressures and thermodynamic sublimation characteristics have been obtained for scandium(III) complexes with acetylacetone, hexafluoroacetylacetone, and 3-methyl-2,4-pentanedione by transpiration and thermogravimetric methods. New data have allowed us to arbitrate the conflict of literature data. As a result, a consistent set of enthalpies of the three discussed processes has been obtained for eight scandium complexes. Dispersion interactions and non-additive effects have been shown to be typical for metal tris-β-diketonates. They have been taken into account to improve the diagnostic check. It is now possible to quite easily assess the thermodynamics of tris-β-diketonate complexes with different metals which are in demand as precursors in gas-phase technology. Full article

We report herein the synthesis and characterization of three heterocyclic curcuminoid ligands and their homoleptic metal complexes with magnesium and copper. Thus, N-methyl-2-pyrrolecarboxaldehyde, Furan-2-carboxaldehyde, and 2-Thiophenecarboxaldehyde were condensed with 2,4-pentanedione-boron trioxide complex. The first N-methyl-2-pyrrole curcuminoid and its Mg(II) complex are reported. All curcuminoid ligands and their corresponding metal complexes were characterized by infrared spectroscopy (IR), liquid state nuclear magnetic resonance (LSNMR), electron paramagnetic resonance (EPR), mass spectrometry (MS) and single crystal X-ray diffraction (SCXRD). The ThiopheneCurc-Cu (9) constitutes the first case of a “conformationally-heteroleptic” complex. The unique six-peaks star arrangement for the ThiopheneCurc ligand derived from the supramolecular description is reported. The metal complexes of FuranCurc-Mg (5) and ThiopheneCurc-Cu (9) have a good antioxidant effect (IC₅₀ = 11.26 ± 1.73 and 10.30 ± 0.59 μM), three and two times higher than their free ligands respectively. Additionally, (5) shows remarkable cytotoxicity against colon cancer adenocarcinoma cell line HCT-15, comparable to that of cisplatin, with a negligible toxic effect in vitro towards a healthy monkey kidney cell line (COS-7). Full article

Isoprenoids, a diverse class of natural products, are present in all living organisms. Their two universal building blocks are synthesized via two independent pathways: the mevalonate pathway and the 2-C-methyl-ᴅ-erythritol 4-phosphate (MEP) pathway. The presence of the latter in pathogenic bacteria and its absence in humans make all its enzymes suitable targets for the development of novel antibacterial drugs. (E)-4-Hydroxy-3-methyl-but-2-enyl diphosphate (HMBPP), the last intermediate of this pathway, is a natural ligand for the human Vγ9Vδ2 T cells and the most potent natural phosphoantigen known to date. Moreover, 5-hydroxypentane-2,3-dione, a metabolite produced by Escherichia coli 1-deoxy-ᴅ-xylulose 5-phosphate synthase (DXS), the first enzyme of the MEP pathway, structurally resembles (S)-4,5-dihydroxy-2,3-pentanedione, a signal molecule implied in bacterial cell communication. In this review, we shed light on the diversity of potential uses of the MEP pathway in antibacterial therapies, starting with an overview of the antibacterials developed for each of its enzymes. Then, we provide insight into HMBPP, its synthetic analogs, and their prodrugs. Finally, we discuss the potential contribution of the MEP pathway to quorum sensing mechanisms. The MEP pathway, providing simultaneously antibacterial drug targets and potent immunostimulants, coupled with its potential role in bacterial cell–cell communication, opens new therapeutic perspectives. Full article

The worldwide known and employed spice of Asian origin, turmeric, receives significant attention due to its numerous purported medicinal properties. Herein, we report an optimized synthesis of curcumin and symmetric curcuminoids of aromatic (bisdemethoxycurcumin) and heterocyclic type, with yields going from good to excellent using the cyclic difluoro-boronate derivative of acetylacetone prepared by reaction of 2,4-pentanedione with boron trifluoride in THF (ca. 95%). The subsequent cleavage of the BF₂ group is of significant importance for achieving a high overall yield in this two-step procedure. Such cleavage occurs by treatment with hydrated alumina (Al₂O₃) or silica (SiO₂) oxides, thus allowing the target heptanoids obtained in high yields as an amorphous powder to be filtered off directly from the reaction media. Furthermore, crystallization instead of chromatographic procedures provides a straightforward purification step. The ease and efficiency with which the present methodology can be applied to synthesizing the title compounds earns the terms “click” and “unclick” applied to describe particularly straightforward, efficient reactions. Furthermore, the methodology offers a simple, versatile, fast, and economical synthetic alternative for the obtention of curcumin (85% yield), bis-demethoxycurcumin (78% yield), and the symmetrical heterocyclic curcuminoids (80–92% yield), in pure form and excellent yields. Full article