Food Chemistry: X最新文献

Roasting is a critical process that influences the aroma of traditional teas. In this study, the effects of microwave roasting (MR), electric conduction roasting (ER), charcoal conduction roasting (CR), steam roasting (SR), and natural shade drying (ND) on the aroma quality of Scutellaria baicalensis Georgi herbal tea (HHT) were systematically evaluated using gas chromatography-mass spectrometry (GC-MS) and electronic nose (E-nose) analysis, and sensory evaluation. The results indicated that MR generated moderate floral-fruity notes and pronounced pyrazines exhibiting roasted characteristics, primarily driven by a balanced Maillard reaction. However, the accumulation of aldehydes and ketones indicated potential oxidation risks. ER further enhanced the roasted characteristics but weakened the floral-fruity notes compared with MR, as intensified lipid oxidation at higher temperatures produced undesirable fatty odors. CR exhibited the most comprehensive aroma profile, characterized by fully released floral-fruity notes, a balanced roasted note, and minimal fatty off-odors. The synergistic effect of radiant heat and a smoky environment promoted terpene glycoside hydrolysis, lipid oxidation, and the Maillard reaction, yielding a harmonious blend of fresh notes and a woody base with the highest complexity. In contrast, SR suppressed the formation of most aroma compounds because of enzyme inactivation and volatile loss under high-temperature, high-humidity conditions, resulting in reduced terpene content and inhibition of the Maillard reaction, though it most effectively eliminated undesirable odors. Due to slow dehydration at low temperatures, ND preserved aroma precursors but exhibited low conversion efficiency, limited enzymatic activity, and continuous degradation of aldehydes and ketones, producing the lowest levels of fresh green and woody notes. Weighted compound co-expression network analysis revealed antagonism between the turquoise module (roasted aroma) and the brown module (fresh floral notes), with the latter demonstrating higher sensitivity to quality variations. The blue module independently reflected oxidative stability. Monitoring the S9/S7 signal ratio enabled precise regulation of roasting parameters, thereby optimizing the Maillard reaction, maintaining aroma balance, and providing early warning of deterioration. Overall, this study elucidated the regulatory mechanisms of different roasting processes on the aroma quality of HHT, providing a basis for production optimization.

This integrated multi-omics study (metabolomics, lipidomics, proteomics) compared the compositions of bovine, caprine, ovine, porcine, and human milk. Human milk is defined by a unique microenvironment where complex human milk oligosaccharides and immune regulating small molecules act together. Components like Lnnt and Lnfp iii form interactive networks, which help modulate both gut microbiota and the immune system. Porcine milk contributes to neural development and immune function. It is rich in polar phospholipids and polyunsaturated fatty acids such as docosahexaenoic acid, important for neural structure and function. Porcine milk also contains specifically high levels of immunoglobulins, including IgM and IgG. In contrast, ruminant milks like bovine and caprine milk show a distinct composition, with high levels of certain functional proteins and active metabolites, such as xanthine dehydrogenase, osteopontin, and allantoin. These findings provide new insights for the precise development of better bovine milk based infant formula and animal milk replacers.

Pukeng tea (PKT), a traditional Chinese dark tea, has been consumed for centuries, yet its volatile and microbial dynamics remain unclear. This study integrated metabolomics, chemometrics, and microbiome analysis to explore PKTs with 3-20 years of storage. HS-SPME-GC-MS identified 189 volatiles, mainly alcohols, aldehydes, and ketones. PCA and PLS-DA revealed distinct metabolite patterns, with 46 differential volatiles, such as 1-butanol and 1-penten-3-ol, characterized as potential discriminants among PKT samples. Microbiota analysis showed 11 dominant bacterial genera, shifting from Firmicutes in early storage to Actinobacteriota in later stages, while Aspergillus dominated fungal communities. Correlation analysis revealed significant associations between dominant microbes such as Staphylococcus and Saccharopolyspora and aroma-active volatiles, suggesting microbial contributions to PKT's evolving flavor. This study provides the first integrated characterization of volatile and microbial diversity in PKT, offering insights into quality control, product authentication, and functional microbe discovery for the sustainable development of traditional dark teas.

Frozen storage is commonly used for preservation of meat products, but it may cause some quality deterioration, due to the repeatedly forming of ice crystals in meat. Effects and action mechanism of tea polyphenols (TP, from 0 to 0.30 g/kg) on the quality of beef meatballs during freeze-thaw cycles were investigated in present study. TP significantly reduced thaw loss of beef meatballs by 36.62% and improved texture (hardness increased by 21.13%, chewiness increased by 18.88%). Low-field nuclear magnetic resonance analysis revealed that TP restricted the conversion of immobilized to free water, decreasing free water by 7.42% and increasing immobilized water by 7.43%. Freezing temperature curve and microstructure image results demonstrated that TP facilitated the rapid formation of uniformly distributed, smaller ice crystals in beef meatballs. After freeze-thaw cycles, TP significantly decreased the content of free sulfhydryl and carbonyl groups of myofibrillar protein, enhanced its surface hydrophobicity and decreased its solubility. Furthermore, multispectral (including fluorescence and infrared spectroscopy) analysis combined with molecular docking indicated that TP could significantly caused a more unfolded secondary structure of myofibrillar protein and expose its hydrophobic centers due to their molecular interaction through hydrogen bonds and hydrophobic interactions. All results suggest that TP show the potential to ameliorate the quality of frozen meat products.

Sulforaphane (SF) is generated from glucoraphanin hydrolysis catalyzed by endogenous myrosinase in Brassicaceae vegetables such as broccoli, with blanching critical to maximize SF formation. However, the effect of magnetic field (MF) treatment on glucoraphanin hydrolysis remains unclear. This study investigated MF-assisted blanching of broccoli florets under 0-10 mT, monitoring myrosinase activity and quantifying SF, sulforaphane nitrile (SFN), and precursor glucosinolates using UPLC-ESI-QTRAP-MS/MS. MF-assisted blanching significantly enhanced myrosinase activity and SF formation, with the greatest effect at 1.0 mT, where myrosinase activity increased 3.11-fold and SF content reached 61.14 ± 1.21 μmol/100 g fresh weight, a 1.89-fold increase relative to the control (blanching only). SFN increased but remained at trace levels, reaching 3.10 ± 0.10 μmol/100 g fresh weight at 1.0 mT versus 0.24 ± 0.09 μmol/100 g in the control. Enhanced hydrolysis was supported by residual glucosinolate levels. These findings suggest a promising strategy to improve SF content in broccoli.

Jasmine green tea (JGT), a distinctive Chinese tea product, derives its unique aroma via the adsorption of volatiles from jasmine flowers onto green tea-base tea (GBT). To identify the key odor-active volatiles in JGT, sensomics and chemometrics were employed, with GBT as the control. Sensory evaluation showed that GBT possesses a clean, fresh, and tender aroma, whereas JGT is characterized by a jasmine-like and refreshing scent. 35 and 31 candidate key odor-active compounds were identified in GBT and JGT, respectively, using aroma extract dilution analysis (FD > 16), and odor activity value analysis (OAV > 1). Aroma recombination, omission, and addition tests confirmed 13 key odor-active volatiles in JGT. Among these, α-farnesene and methyl salicylate were found to be the primary contributors to the jasmine-like and refreshing aromas, respectively. This study provides a theoretical reference for deeply understanding the molecular basis of JGT's aroma characteristics.

Utilization of commercial pea protein (PP) in food emulsions largely depends on empirical experience due to insufficient knowledge. Emulsions made of seven commercial PP ingredients by high-pressure homogenization (HPH) were studied and uncovered their relationship with physicochemical and interfacial properties of homogenized PP. Results showed that HPH produced PP supernatants of varying size and composition, leading to differences in interfacial adsorption of emulsions. Four emulsions had very small droplets (1.1-2.7 μm), in contrast to one with medium sized droplets (5.8 μm) and two with large droplets (> 10 μm). The oil droplet size was highly correlated with the protein content and size in the soluble phase, suggesting that emulsification was mainly driven by soluble proteins after homogenization. Moreover, small droplet size was not a prerequisite to flocculation and coalescence stability. During storage, emulsions showed different mechanisms of destabilization. Overall, these results provided an accurate assessment of commercial PPs as emulsifiers, aiding the development of predictive models.

Thermal sterilization significantly influences milk aroma, which is a key factor affecting consumer acceptability. This study employed molecular sensory science to characterize aroma profiles and key aroma-active compounds (AACs) of raw and four thermally sterilized milks. High-intensity sterilization enhanced the milky, fatty, and sweet attributes. Eighty volatiles were identified using a self-built milk flavor database, and 45 odorants were sniffed with flavor dilution (FD) factors of 1-64. Twenty-six odorants (FD ≥ 8) were quantified using external standard calibration. To further improve the precision of quantification, eight AACs (FD ≥ 64; odor activity values ≥1) were quantified by stable isotope dilution analysis for the first time. Recombination and omission experiments revealed 16 key AACs, of which 1-octen-3-ol and butyric acid represented key contributors across five milks, octanal, nonanal, γ-nonalactone, and 2(5H)-furanone were key contributors in the sterilized milks. These findings provide a scientific basis for optimizing milk sterilization processes.

Drying is a critical processing step in the production of Camellia nitidissima Chi (CN)-scented tea. We investigated the effects of hot-air drying (HAD) and vacuum freeze-drying (VFD) on non-volatile and volatile compounds in CN flowers and their tea infusions, utilizing mass spectrometry. Both methods reduced CN moisture to below 8% and significantly reduced volatile compound concentrations. VFD-treated flowers exhibited better morphology and higher levels of flavonoids, polyphenols, and lipids, thereby enhancing antioxidant capacity; while HAD promoted the upregulation of stress-related metabolites, such as phenolic acids. Moreover, VFD flower infusion showed greater diversity and significantly higher concentrations of non-volatile metabolites, especially lipids and flavonoids (anthocyanins, isoflavones). 78.3% of differential aroma compounds (VIP > 1) had higher relative odor activity than infusions from fresh and HAD flowers. These results may underscore VFD as the preferred method for retaining both the nutritional and sensory attributes of CN flowers and their tea infusions.

This study investigated the effects of different pretreatment media-NaCl solution (NaCl aq.), sucrose solution (Suc aq.), and deionized water (DW)-on the combined ultrasonic (US)-electrohydrodynamic (EHD) drying of garlic. Comprehensive analysis revealed that the NaCl aq. + US pretreatment demonstrated optimal performance. It markedly improved the effective moisture diffusion coefficient (D _eff ), thereby accelerating the overall drying kinetics, and enhanced the rehydration capacity, indicating better preservation of the garlic's microstructure. This pretreatment also promoted superior retention of allicin-derived compounds and total phenols compared to other methods. Furthermore, it helped preserve protein secondary structure, promoted the release of alliinase, and maximized the content of volatile sulfur compounds. These findings first reveal the synergistic mechanism of medium-regulated ultrasound, where osmotic pressure and cavitation effects jointly enhance bioactive compound retention. The results provide both theoretical and practical support for optimizing combined drying processes in garlic processing.