Seasonal variation in non-volatile flavor substances of fresh tea leaves (Camellia sinensis) by integrated lipidomics and metabolomics using UHPLC-Q-Exactive mass spectrometry.

Harvest season exerts great influence on tea quality. Herein, the variations in non-volatile flavor substances in spring and summer fresh tea leaves of four varieties were comprehensively investigated by integrating UHPLC-Q-Exactive based lipidomics and metabolomics. A total of 327 lipids and 99 metabolites were detected, among which, 221 and 58 molecules were significantly differential. The molecular species of phospholipids, glycolipids and acylglycerolipids showed most prominent and structure-dependent seasonal changes, relating to polar head, unsaturation and total acyl length. Particularly, spring tea contained higher amount in aroma precursors of highly unsaturated glycolipids and phosphatidic acids. The contents of umami-enhancing amino acids and phenolic acids, e.g., theanine, theogallin and gallotannins, were increased in spring. Besides, catechins, theaflavins, theasinensins and flavone/flavonol glycosides showed diverse changes. These phytochemical differences covered key aroma precursors, tastants and colorants, and may confer superior flavor of black tea processed using spring leaves, which was verified by sensory evaluation.

Development of Methodology for molecular crystallization of Menthol.

Menthol, terpene alcohol with a strong minty, cooling odor and taste is highly popular in food, flavor, cosmetic and pharmaceutical industries. Crystallization of menthol from mint oil is a tedious process involving high cost and a much longer period. The present study has been undertaken to devise a new method with low input and with higher production rates. The crystallization of menthol was performed by the methods including Temperature programmed cooling process (TPCP); Short-path molecular fractional distillation (SPMFD) and Stripping crystallization (SC). About 99 % menthol contained in the mint oil was recovered during the crystallization process. The characterization techniques such as scanning electron microscopy (SEM) for surface morphology, x-ray diffraction (XRD) for crystal structure and crystallite size evaluation, and FTIR and Raman spectroscopy for analyzing the chemical nature of the crystals.

Unveiling the potential applications of buds of Lonicera japonica Thunb. var. chinensis (Wats.) Bak based on in vitro biological activities, bio-active components, and potential applications coupled to targeted metabolomics.

Introduction: The buds of Lonicera japonica Thunb. var. chinensis (Wats.) Bak, commonly named red honeysuckle, have attracted attention because of their bright colors. However, owing to the lack of systematic studies, the potential applications of red honeysuckle are not clear, and its development and utilization have not been well known. Methods: In this study, compared with the buds of L. japonica Thunb. (honeysuckle), the potential applications of red honeysuckle were explored based on biological activities, bio-active components, and sensory flavor combined with widely targeted metabolomics. Results: As a result, in vitro tests showed that it had a stronger antioxidant and a stronger inhibitory effect on the growth of Escherichia coli and Staphylococcus aureus. There was no cytotoxicity on LPS-induced RAW264.7 cells in its aqueous extract using the CCK-8 method. Moreover, it also had a stronger effect on inhibiting the expression of inflammatory factors such as interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interleukin-1ß (IL-1ß). The content of its bio-active components chlorogenic acid and cynaroside was significantly higher (p ≤ 0.001) than that of green honeysuckle. Widely targeted metabolomics analysis revealed that 4 volatile metabolites, such as (E)-4-hexene-1-ol and pyrazole, and 21 non-volatile metabolites, such as macranthoside B and oleanolic acid-3-O-glc(1-2)-(ara)-28-O-glucoside ester, were specific in red honeysuckle. Interestingly, 14 specific terpenoid metabolites were triterpenoid saponins, indicating a stronger biological activity in red honeysuckle. The sensory flavor analysis showed that the red honeysuckle had a stronger herbal and lighter floral flavor. Discussion: In conclusion, red honeysuckle had great development value with potential applications in medicines, foods, beverages, pigment additives, and health products.

Characterization and discrimination of volatile organic compounds and α-glucosidase inhibitory activity of soybeans (Glycine max L.) during solid-state fermentation with Eurotium cristatum YL-1.

In this study, the influence of solid-state fermentation (SSF) using probiotic Eurotium cristatum on the change of volatile organic compounds (VOCs) and α-glucosidase inhibition activity of soybeans was investigated. A total of 46 VOCs were characterized via headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS), the majority of which were aldehydes (17), alcohols (10), and ketones (7). SSF by E. cristatum drastically affected the flavor characteristics of soybeans, and the levels of unpleasant beany flavor components, such as hexanal-D, 1-octen-3-ol, 1-hexanol-D, 1-hexanol-M, heptanal-M, 1-pentanol, heptanal-D, and 2-pentyl furan were all substantially decreased by 50% after 15 days of SSF, while volatiles with floral, caramel, and desirable flavors such as pentanal-D, methylpropanal, 2-propanol, and propyl acetate drastically (p < 0.05) increased by 1.1-, 19.2-, 3.6-, and 2.6-fold, respectively. Key aroma-active compounds analysis revealed that 18 VOCs (ROAV, relative odor activity value ≥ 1) play a great role in shaping the flavor characteristics of the soybean samples. After 15 days of SSF, the ROAV values of methylpropanal, 2-propanol, and propyl acetate drastically (p < 0.05) increased to 8.48, 63.88, and 11.29, respectively, which greatly contributed to the desirable flavor characteristics of fermented soybeans. Furthermore, E. cristatum greatly improved the α-glucosidase inhibitory activity of soybean by 22.4% after 15 days fermentation, which was closely correlated with the accumulated phenolic compounds during SSF. Molecular docking showed that genistein and daidzein have high binding affinity for α-glucosidase active sites, primarily driven by hydrogen bonds and hydrophobic interactions. These results demonstrated that soybeans fermented with E. cristatum substantially improved the flavor characteristics and α-glucosidase inhibitory effect, and were greatly helpful to promote the application of soybeans in food products.

Characterization of fine-flavor cocoa in parent-hybrid combinations using metabolomics approach.

Fine-flavored cocoa is generally characterized by fresh bean color and sensory characteristics. However, these methods cannot be applied to progenies/hybrids because their colors may vary depending on their parents. Additionally, sensory evaluation lacks universal quality standards, necessitating robust complementary characterization methods. This study aimed to characterize the fine-flavor cacao in parent-hybrid combinations using widely targeted Gas Chromatography-Mass Spectrometry (GC-MS) and bean phenotype analysis. Fine-flavored cacao exhibits white-bean characteristics and a lighter color than forastero. Conversely, the hybrids displayed varying percentages of fresh bean color. Caffeine and organic acids (malic acid, fumaric acid, citric acid, lactic acid, and tartaric acid) were found to correspond to the characteristics of fine-flavored cacao. Each parent-hybrid combination demonstrated distinct flavor characteristics, with the ICCRI03-hybrid emerging as a promising clone, exhibiting flavor characteristics similar to those of its female parent (fine-flavor cacao). This information on flavor characteristics will be beneficial for further fine-flavored cacao selection.

Harnessing nature's catalysts: Advances in enzymatic alkene cleavage.

Double bonds are prevalent in various substrates and renewable feedstocks, and their cleavage typically necessitates harsh reaction conditions involving high temperatures, organic solvents, and hazardous catalysts such as heavy metals or ozone. This review explores the sustainable enzymatic alternatives developed by nature for alkene cleavage. It provides a comprehensive overview of alkene-cleaving enzymes, detailing their mechanisms, substrate specificities, and applications. The enzymes discussed include those acting on aliphatic, cyclic, and activated aromatic systems. Emphasizing the significance of these biocatalysts in green chemistry and biocatalysis, this review highlights their potential to replace traditional chemical oxidants with safer, cost-effective, and environmentally friendly options. Future research directions include expanding enzyme substrate scopes, enhancing their operational stability and activity, and integrating them into scalable processes for broader application in the pharmaceutical, flavor, and fragrance industries.

Dynamic changes in aromas and precursors of edible fungi juice: mixed lactic acid bacteria fermentation enhances flavor characteristics.

BACKGROUND: Lactic acid bacteria (LAB) fermentation technology has been increasingly used in the deep processing of edible fungi. However, the flavor profiles of edible fungi products after mixed LAB fermentation have received less attention and how aromas changes during the mixed LAB fermentation are still open questions. In the present study, fermented Hericium erinaceus and Tremella fuciformis compound juice (FHTJ) was prepared by mixed LAB strains. We aimed to systematically monitor the dynamic changes of aromas and precursors throughout the fermentation process and a data-driven association network analysis was used to tentatively illustrate the mechanisms of formation between aromas and their precursors. RESULTS: Mixed LAB fermentation could enrich the aroma profile of FHTJ, reducing the unpleasant flavors such as nonanal and 1-octen-3-ol, as well as increasing the floral flavors such as ethyl acetate and α-pinene. Partial least squares-discriminant analysis and relative odor activity values revealed that 11 volatile chemicals were recognized as aroma-active markers. Volcano plot analysis showed that 3-octen-2-one (green flavor) was the key aroma-active marker in each stage, which was down-regulated in fermentation stages I, II and IV, whereas it was up-regulated in stage III. 3-Octen-2-one was significantly negatively correlated with organic acids, particularly pyruvate (r2 = -0.89). Ethyl caprylate (floral flavor) was up-regulated in the late fermentation stage, and showed a negative correlation with sugar alcohols and a positive correlation with organic acids, especially tartaric acid (r2 = 0.96). CONCLUSION: The present study demonstrates the beneficial effect of mixed LAB fermentation on flavor characteristics, providing guidance for fermented edible fungi juice flavor quality monitoring and control. © 2024 Society of Chemical Industry.

Effects of yeast cultures on meat quality, flavor composition and rumen microbiota in lambs.

Since the banning of antibiotics, the use of feed additives to improve meat quality to satisfy people's pursuit of high quality has become a research hotspot. Yeast culture (YC) is rich in proteins, mannan oligosaccharides, peptides, and yeast cell metabolites, etc., and its use as a feed additive has a positive impact on improving meat quality. So the study aimed to provide a theoretical basis for YC improving mutton flavor and quality by detecting and analyzing the effects of YC on muscle physicochemical properties, amino acids, fatty acids, flavor composition, expression of related genes, and rumen microbiota of lambs. A total of 20 crossbred F1 weaned lambs (Australian white sheep♂ × Hu sheep♀; average 23.38 ± 1.17 kg) were randomly assigned to 2 groups, the control group (CON) and the 1.0% YC supplemented group (YC) (n = 10), and were reared in separate pens. The experiment had a pre-feeding period of 10 d and a treatment period of 60 d. After the experiment, 6 lambs in each group were randomly selected for slaughtering. The results showed that dietary YC supplementation increased rumen total VFA and acetate concentrations (p < 0.05), and muscle carcass fat (GR), a∗ value, intramuscular fat (IMF), lysine (Lys), arginine (Arg), nonessential amino acid (NEAA), oleic acid (C18:1n9c), and eicosanoic acid (C20:1) contents were significantly increased (p < 0.05), while cooking loss and γ-linolenic acid (C18: 3n6) were decreased (p < 0.05). Furthermore, we found that dietary YC improved the types of flavor compounds, and the key flavor substances such as hexanal, nonanal, styrene, benzaldehyde, p-xylene, and 1-octen-3-ol contents were changed (p < 0.05). Additionally, the expression of fat metabolism related genes PPARγ, FASN, and FABP4 were increased. Adding 1% YC to lamb diets increased profits by 47.70 CNY per sheep after 60 d of fattening. All of which indicated that YC could improve meat quality, especially flavor, which may be related to the regulation of the relative abundance of rumen microorganisms Bacteroidota, Prevotella_7, Succiniclasticum and Lachnospiraceae_NK3A20_group.

Formulation of a novel hot pot dipping sauce enriched with pepper seed press cake: Physical properties and flavor characteristics.

Novel hot pot dipping sauces enriched with pepper seed press cake (PSPC) in five proportions were prepared and evaluated in terms of their physical properties and flavor characteristics. The findings indicated that enriching the sauce increased the content of palmitic and linoleic acids, enhanced storage stability, and improved the rheological behavior and textural properties. The maximum concentration of N-heterocyclic compounds was detected when PSPC was added at 5 g/100 g and 10 g/100 g. A suitable amount of PSPC could improve the mouthfeel and intensify the flavors of umami and saltiness. In comparing sauces with different amounts of PSPC added (0-20 g/100 g), the quality, aroma, and taste were better and overall acceptance was highest when PSPC was added in the range of 5 g/100 g to 10 g/100 g. This study provides a possible application of PSPC for improving the flavor, texture, nutritional quality, and storage stability of hot pot dipping sauce.

A strategy of Q-markers identification based on effect, property flavour material basis and rapid quantitative evaluation via near-infrared spectroscopy and chemometric methods for the quality control of Flos Trollii (FT).

ETHNOPHARMACOLOGICAL RELEVANCE: Flos Trollii (FT) is the dried flower of Trollius Chinensis Bunge of Ranunculaceae with the pharmacological properties of anti-inflammatory, antibacterial, antiviral, anti-oxidative. The herb FT is not only a traditional Chinese medicine (TCM) but also an extensively utilized ethnic medicine, employed by diverse ethnic groups including Mongolian, Tibetan, and Kazakh. AIM OF STUDY: FT was taken as an example to construct a strategy of quality markers (Q-markers) identification based on effect, property flavor material basis, and rapid quantitative evaluation using near-infrared (NIR) spectroscopy and chemometric methods of TCM. MATERIALS AND METHODS: Initially, the anti-inflammatory efficacy of FT from three places of origin was evaluated using the RAW264.7-cell inflammatory model, and the bitter property flavor was characterized using an electronic tongue. The high-performance liquid chromatography(HPLC) fingerprint of FT was generated, and the quality of FT from different origins was evaluated employing chemometrics. Next, potential anti-inflammatory and bitter property flavor compounds were screened utilizing a fingerprinting-effect relationship and fingerprinting-property flavor relationship model using partial least squares regression (PLSR). The Q-markers of the FT were confirmed based on the testability principle. Then, a swift, uncomplicated, and precise Q-marker content of the FT prediction model was developed by adopting NIR. RESULTS: The main common fingerprinting peaks affecting FT's efficacy and property flavor were screened. Five of these compounds, 2"-O-beta-L-galactopyranosylorientin, orientin, vitexin, veratric acid, and isoquercitrin, characterized using HPLC and ultra-high performance liquid chromatography(UPLC-QTOF-MS), could be regarded as Q-markers of FT. Q-marker content of the FT prediction model developed adopting NIR spectroscopy was rapid and effective. CONCLUSION: According to the strategy proposed in this study, a quantitative NIR spectroscopic method to identify Q-markers could be a tool to improve the QC efficiency of TCM.

Interaction and dynamic changes of microbial communities and volatile flavor compounds during the fermentation process of coffee flower rice wine.

To develop a unique flavor of rice wine, coffee flowers (by-products of the coffee industry) were added because of their biologically active compounds that are conducive to health, and the fermentation parameters were optimized. In addition, the dynamic changes of microbial communities and volatile flavor compounds (VFCs) during the different fermentation stages were investigated. After the optimization of the fermentation parameters, a novel product, i.e., the coffee flower rice wine (CFRW), was obtained with a bright yellow transparent, fragrant, and harmonious aroma and mellow and refreshing taste by sensory evaluation, when 4.62% of the coffee flowers and 1.93% koji were added and fermented at 24.10°C for 3.88 days. The results showed that Lactococcus was the dominant bacteria, accounting for 87.0-95.7%, while Rhizopus and Cladosporium were the main fungi, accounting for 68.2% and 11.3% on average, respectively, in the fermentation process of the CFRW. Meanwhile, twenty-three VFCs were detected in the CFRW, which included three alcohols, six terpenes, ten esters, three aromatics, and one furan. The correlation analysis revealed that there were 16 significant positive correlations and 23 significant negative correlations between the bacterium and VFCs (|ρ| > 0.6, p < 0.05), while there were 12 significant positive correlations and one significant negative correlation between the fungi and VFCs (|ρ| > 0.6, p < 0.05). Furthermore, five VFCs, including linalool, geraniol, ethyl acetate, 1-hexanol, and 3-methyl-1-butanol, contributed vital flavors to the CFRW, and they were all significantly negatively correlated with the changes of Massilia and Acinetobacter (|ρ| > 0.6, p < 0.05). Moreover a significant positive correlation was found between the relative abundance of Lactococcus and the contents of 3-methyl-1-butanol and ethyl acetate (|ρ| > 0.6, p < 0.05). Therefore, this study provides a valuable theoretical basis for further improving the quality and production technology of CFRW.

Study on the differentiation of sensory quality of mainstream Jiang-flavor baijiu in the Chinese market based on Pivot Profile.

Jiang-flavor baijiu (JFB) is a prominent type of Chinese baijiu, known for its unique flavor attributes, sensory experience, and high tasting value. Previous research has mainly focused on the detection and identification of its flavor substances, but in-depth studies on the precise sensory description and differentiation of its flavor qualities are still lacking. In this study, a rapid sensory analysis method, Pivot Profile (PP), was applied to 30 mainstream JFBs in the Chinese market, generating 91 sensory attributes with independent definitions, from which 29 main sensory attributes were established that were easy to perceive and descriptive, as well as convenient for transmitting their sensory qualities and distinguishing differences in price and production region, including color (one descriptor), aroma (21 descriptors), taste, and mouthfeel (seven descriptors). The nine key sensory attributes that distinguish JFB quality are as follows: Jiang, Grain, Chen, Qu, Rancid, Acid, Sweet, Fullness, and Harmony. It was found that price was positively correlated with sensory quality, with greater variation in the quality of samples within the medium price range (RMB 500-1000). All samples from MTCQ1 (the core production area of Maotai Town) performed better in sensory quality. In addition, salted vegetable showed a high degree of regional characteristics, concentrated in most of the production regions of Guizhou Province. Aroma attributes were more suitable than taste and mouthfeel as sensory indicators for distinguishing production regions. This study has opened the direction of systematic construction of sensory description of JFB and provided a successful case for the evaluation of Chinese baijiu using novel sensory analysis techniques.

Establishment, characterization, and sensory characteristics (taste and flavor) of an immortalized muscle cell line from the seven-band grouper Epinephelus septemfasciatus: implications for cultured seafood applications.

Grouper muscle satellite cells (GMSCs) from the seven-band grouper (Epinephelus septemfasciatus) were isolated, and their growth conditions were optimized (10% fetal bovine serum, 24°C, 10 ng/mL bFGF). The cells were immortalized at passage 14 and designated as grouper immortalized muscle satellite cells (GIMSCs). DNA barcoding confirmed the grouper origin of both GMSC and GIMSC lines. GIMSCs exhibited enhanced proliferation, accelerated differentiation, and robust myotube formation compared to pre-crisis GMSCs. Western blot analysis showed upregulation of key myogenic factors (Pax7, MyoD, MyoG) and structural proteins (Desmin) in GIMSC, indicating the differentiation potential. The immortalized GIMSC line maintained consistent morphology, growth rates, and viability across multiple passages. Biocompatibility studies showed GIMSCs were compatible with bio-inks (sodium alginate, gelatin, κ-carrageenan) at 250 to 10,000 µg/mL, retaining ~ 80% viability at the highest concentration. Taste sensory analysis revealed GMSCs had the highest umami and lowest saltiness and sourness, contrasting with the muscle of the seven-band grouper, which had higher saltiness and sourness. Flavor analysis identified pronounced fishy, hot fat, and ethereal flavors in the cells at higher level than in the muscle. These findings suggest GMSCs and GIMSCs are promising for producing cultured meat with enhanced umami taste and flavors, advancing cellular agriculture and sustainable food production.

The application of untargeted metabolomics coupled with chemometrics for the analysis of agitation effects on the sensory profiles of matcha tea.

In the study, the effects of agitating parameters (different agitating rates and time) on the aroma and taste profiles of matcha tea were systematically investigated by the combination of untargeted metabolomics and chemometrics. The aroma profiles of matcha tea agitated at low rates (500 rpm) and for 30 s were more richness than that agitated with other parameters by sensory analysis and gas chromatography-ion mobility spectrometry. The key aroma compounds contributed to the sensory differences of matcha tea agitated at different rates and time were analyzed by gas chromatography-mass spectrometry and partial least square-discriminate analysis (PLS-DA), which were further verified by the triangle test. Thereinto, 2,4-decadienal associated with the sweet, brown and seaweed aroma significantly affected the aroma profiles of matcha tea with different agitating rates and time. The levels of bitterness and astringency were also higher in matcha tea with low agitating rates and time by sensory evaluation, which were attributed to the variations of phenolic compounds. Flavonol glycosides, gallic acid and (-)-gallocatechin were determined the key compound to the taste differences of matcha tea with different agitating parameters by the analysis of PLS-DA based on the results of high performance liquid chromatography and the sensory verification. And flavonol glycosides were mainly contributed to the bitterness and astringency, and gallic acid and (-)-gallocatechin influenced the umami and sweetness of matcha tea. Consequently, agitation has the potential to affect the sensory profiles of matcha tea by changing aroma and taste substances.

Effect of Isolated Scenting Process on the Aroma Quality of Osmanthus Longjing Tea.

Scenting is an important process for the formation of aroma quality in floral Longjing tea. There are differences in the aroma quality of osmanthus Longjing teas processed by different scenting processes. The efficient isolated scenting method was employed to process a new product of osmanthus Longjing tea in this study, and this was compared with the traditional scenting method. The volatile compounds of osmanthus Longjing tea were analyzed by a GC-MS instrument. In addition, the effects of scenting time and osmanthus consumption on the aroma quality of Longjing tea were studied. The results indicated that there were 67 kinds of volatile compounds in the osmanthus Longjing tea produced by the isolated scenting process (O-ISP), osmanthus Longjing tea produced by the traditional scenting process (O-TSP), and raw Longjing tea embryo (R), including alcohols, ketones, esters, aldehydes, olefins, acids, furans, and other aroma compounds. The proportions of alcohol compounds, ester compounds, aldehyde compounds, and ketone compounds in O-ISP were higher than in O-TSP and R. When the osmanthus consumption was increased, the relative contents of volatile aroma compounds gradually increased, which included the contents of trans-3,7-linalool oxide II, dehydrolinalool, linalool oxide III (furan type), linalool oxide IV (furan type), 2,6-Dimethyl cyclohexanol, isophytol, geraniol, 1-octene-3-alcohol, cis-2-pentenol, trans-3-hexenol, ß-violet alcohol, 1-pentanol, benzyl alcohol, trans-p-2-menthene-1-alcohol, nerol, hexanol, terpineol, 6-epoxy-ß-ionone, 4,2-butanone, 2,3-octanedione, methyl stearate, cis-3-hexenyl wasobutyrate, and dihydroanemone lactone. When the scenting time was increased, the relative contents of aroma compounds gradually increased, which included the contents of 2-phenylethanol, trans-3,7-linalool oxide I, trans-3,7-linalool oxide II, dehydrolinalool, isophytol, geraniol, trans-3-hexenol, ß-ionol, benzyl alcohol, trans-p-2-menthene-1-ol, nerol, hexanol, terpineol, dihydroß-ionone, α-ionone, and ß-ionone,6,10. The isolated scenting process could achieve better aroma quality in terms of the floral fragrance, refreshing fragrance, and tender fragrance than the traditional scenting process. The isolated scenting process was suitable for processing osmanthus Longjing tea with high aroma quality. This study was hoped to provide a theoretical base for the formation mechanism and control of quality of osmanthus Longjing tea.

Effect of High-Pressure Processing Treatment on the Physicochemical Properties and Volatile Flavor of Mercenaria mercenaria Meat.

High-pressure processing (HPP) technology can significantly improve the texture and flavor of Mercenaria mercenaria. This study aimed to investigate the effect of HPP treatment with varying levels of pressure (100, 200, 300, 400, 500, and 600 MPa) and a holding time of 8 min at 20 °C on the physicochemical properties and volatile flavors of M. mercenaria. The significant changes in hardness, resilience, and water holding capacity occurred with increasing pressure (p < 0.05), resulting in improved meat quality. Scanning electron microscopy (SEM) was utilized to observe the decomposition of muscle fibers in M. mercenaria due to varying pressures, which explains the differences in texture of M. mercenaria. Different pressure treatments also had an influence on the volatile flavor of M. mercenaria, and the quantities of low-molecular-weight aldehydes (hexanal, heptanal, and nonanal) with a fishy taste decreased dramatically following 400 and 500 MPa HPP treatments. Furthermore, the level of 2-Methylbutyraldehyde, which is related to sweetness, increased significantly following 400 MPa HPP treatment. The study found that 400 MPa HPP treatment resulted in minor nutrient losses and enhanced sensory quality. The results of this study provide a theoretical basis for the application of HPP treatment to M. mercenaria.

Insight into konjac glucomannan-retarding deterioration of steamed bread during frozen storage: Quality characteristics, water status, multi-scale structure, and flavor compounds.

Konjac glucomannan (KGM), a water-soluble hydrocolloid, holds considerable potential in the food industry, especially for improving the quality and nutritional properties of frozen products. This study explored the alleviative effect of KGM on the quality characteristics, water status, multi-scale structure, and flavor compounds of steamed bread throughout frozen storage. KGM significantly improved the quality of steamed bread by slowing down the decrease in water content and the increase in water migration while maintaining softness and taste during frozen storage. Notably, KGM also delayed amylopectin retrogradation and starch recrystallization, thus preserving the texture and structure of the steamed bread. At week 3, the microstructure of the steamed bread with 1.0 % KGM remained intact, with the lowest free sulfhydryl content. Additionally, heat map analysis revealed that KGM contributed to flavor retention in steamed bread frozen for 3 weeks. These results indicate that KGM holds promise as an effective cryoprotectant for improving the quality of frozen steamed bread.

Improving common vetch protein isolate flavor through glutaminase-mediated deamidation.

Common vetch protein, similar to pea protein, offers valuable qualities like being non-GMO, hypoallergenic, and nutritious. However, its strong beany flavor hinders consumer acceptance. This study explores enzymatic deamidation using glutaminase to address this issue. GC-MS analysis identified 54 volatile compounds in the raw material protein, with 2-pentylfuran, hexanal, and several nonenals contributing the most to the undesirable aroma. Principal component analysis (PCA) confirmed the effectiveness of glutaminase deamidation in removing these off-flavors. The study further reveals that deamidation alters the protein's secondary structure, with an increase in α - helix structure and a decrease in ß - sheet structure. The surface hydrophobicity increased from 587.33 ± 2.63 to 1855.63 ± 3.91 exposing hydrophobic clusters that bind flavor compounds. This disruption weakens the interactions that trap these undesirable flavors, ultimately leading to their release and a more pleasant aroma. These findings provide valuable insights for enzymatic deodorization of not only common vetch protein but also pea protein.

Effect of fatty acid composition on the volatile compounds of pasteurized milk during low-temperature storage.

The change in milk fat during storage greatly influences its flavor. This study investigates the effect of fatty acid composition on milk flavor by analyzing volatile compounds in pasteurized whole milk (PWM) and pasteurized skim milk (PSM) during storage at 4 °C. 33 types of volatile compounds were detected and the content of ketones was highest, followed by esters and aldehydes. Based on variable importance in projection and relative odor activity value, 2-hexenal dimer, acetic acid ethyl ester dimer, acetic acid ethyl ester, and butanal were identified as the key differential volatile compounds. These compounds were found in higher concentrations in PWM than in PSM, indicating a close relationship with the changes in the fatty acid composition of milk fat. Among 11 fatty acids detected in PWM, the content of saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) decreased by 0.69 % and 49.1 %, respectively, while the content of monounsaturated fatty acids increased by 46.8 % during 15 days storage, which suggests that the oxidation of SFA and PUFA contributed more to the volatile compound formation. Correlation analysis between fatty acid composition and volatile compounds found that fatty acid C18:2 and C16:0 were strongly associated for 2-hexenal, acetic acid ethyl ester, and butanal. These fatty acids were mainly derived from neutral lipids or phospholipids. These findings provide a new perspective for the formation pathway of milk flavor.

Metabolomics ravels flavor compound formation and metabolite transformation in rapid fermentation of salt-free fish sauce from catfish frames induced by mixed microbial cultures.

This study demonstrates that the co-inoculation with Lactiplantibacillus plantarum, Pichia fermentans and Staphylococcus saprophyticus accelerates catfish frame fish sauce fermentation. Over a 3-day period, significant changes occurred in physicochemical properties, microbial profiles, flavor compounds, and metabolomic spectra. Notable increases in acidity coupled with decreases in glucose underscored the robust environmental adaptability of the employed microorganisms. A reduction in total amino acids, alongside a rise in umami amino acids, suggested flavor enhancement. GC-MS analysis identified 40 key volatile compounds, with esters and aldehydes crucial for aroma development. UPLC-QTOF-MS-based untargeted analysis identified 934 metabolites, with 377 differential metabolites being vital (VIP > 1.5, P < 0.05), including amino acids, peptides, organic acids, nucleic acids, and fatty acids. Metabolites linked to amino acid metabolism, particularly phenylalanine and arginine, were associated with fermentation duration. These findings offer a theoretical basis for optimizing flavor and quality in fish sauces from fish by-products through accelerated fermentation.