Analysis of the changes of volatile flavor compounds in a traditional Chinese shrimp paste during fermentation based on electronic nose, SPME-GC-MS and HS-GC-IMS

Characterization and exploration of dynamic variation of volatile compounds in vine tea during processing by GC-IMS and HS-SPME/GC-MS combined with machine learning algorithm

It is imperative to unravel the dynamic variation of volatile components of vine tea during processing to provide guidance for tea quality evaluation. In this study, the dynamic changes of volatile compounds of vine tea during processing were characterized by GC-IMS and HS-SPME/GC-MS. As a result, 103 volatile compounds were characterized by the two technologies with three overlapped ones. The random forest approach was employed to develop the models and explore key volatile compounds. 23 key compounds were explored, among which 13 were derived from GC-IMS and ten were from HS-SPME/GC-MS. Moreover, the area under the receiver operating characteristics curve with 100 cross validations by the pair-wised models were all 1 for the established models. Furthermore, the primary aroma formation mechanism for the key volatile compounds were mainly involved in fatty acid and amino acid metabolism. Besides, this study provides a theoretical support for directed processing and quality control of vine tea.

Volatile flavor profiles of douchis from different origins and varieties based on GC-IMS and GC-O-QTOF/MS analysis

The present study comprehensively characterized the flavor differences between different varieties of douchis from different origins using headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) coupled with gas chromatography-olfactometry-quadrupole time-of-flight mass spectrometry (GC-O-QTOF/MS). A total of 91 volatile organic compounds (VOCs) were identified using HS-GC-IMS and 70 VOCs were identified using GC-O-QTOF/MS, mainly including acids, aldehydes, esters and alcohols. Additionally, 23 key aroma-presenting compounds were screened in five douchi species using relative odor activity value (ROAV) and the aroma compounds that contributed the most to the aroma varied among the five douchi species. Comparative analysis of the GC-IMS and GC-O-QTOF/ MS results yielded 13 VOCs that were detected by both techniques. Nonanal, hexanal, eucalyptol, 1-octen-3-ol, isoamyl acetate, and 2-pentylfuran were identified as key VOCs in the douchi species using both methods. These findings will provide deeper insights for exploring flavor differences in douchi from different geographic sources.

Recent advances in signal processing algorithms for electronic noses

Electronic nose (e-nose) technology has emerged as a pivotal tool in various domains, which has been widely utilized for odor identification, concentration evaluation, and prediction tasks. This review provides a comprehensive survey on the most recent advances in the development of e-nose systems and their algorithmic applications, emphasizing the roles of various methodologies and deep learning technologies in odor classification and concentration forecasting. Additionally, we delve into model evaluation methods, including multidimensional performance assessment and cross-validation. Future trends encompass broader application domains, advanced drift correction techniques, comprehensive multifactorial analysis, and enhanced capabilities for dealing with unknown interferents. These trends are set to propel significant breakthroughs in e-nose technology within scientific research and practical applications, solidifying the e-nose system as a crucial tool in many areas such as environmental monitoring, biomedicine, and public safety.

The dynamic changes of flavor characteristics of sea cucumber (Apostichopus japonicus) during puffing revealed by GC-MS combined with HS-GC-IMS

To improve the ease of eating sea cucumbers, we investigated the impact of puffing temperature (190 °C - 250 °C) and time (1-5 min) on their quality and flavor. As temperature and time increased, sea cucumber puffing significantly enhanced. The microstructure of the puffed sea cucumber exhibited a uniform porous structure at 230 °C for 4 min. However, further puffing treatment caused the void to collapse. A total of 81 volatile organic compounds (VOCs) were identified using HS-GC-IMS, and 18 VOCs with Relative odor activity value (ROAV) ≥1 were identified. The content of fishy compounds, such as dimethyl sulfide, 1-octanal, and 1-nonanal in sea cucumbers gradually decreased with increasing temperature and time. Combined with GC-MS analysis indicating that the flavor of sea cucumbers puffed at 250 °C for 5 min was superior. Our findings suggest new avenues for sea cucumber processing and address the limited research on puffing techniques for protein-based raw materials.

Correlation between physicochemical properties, flavor characteristics and microbial community structure in Dushan shrimp sour paste

Dushan shrimp sour paste (DSSP), a traditional Guizhou condiment, and its unique flavor is determined by the fermentation microbiota. However, the relationship between the microbiota structure and its flavor remains unclear. This study identified 116 volatile flavor compounds using electronic nose and headspace solid-phase microextraction-gas chromatography mass spectrometry (HS-SPME-GC-MS) techniques, of which 19 were considered as key flavor compounds, mainly consisting of 13 esters and 1 alcohol. High-throughput sequencing technique, the bacterial community structure of nine groups of DSSPs was determined. Further analysis revealed Vagococcus, Lactococcus, and Tepidimicrobium as key bacteria involved in flavor formation. This study contributes to our understanding of the relationship between bacterial communities and the flavor formation, and provides guidance for screening starter culture that enhance the flavor of DSSP in industrial production.

Integrated characterization of arabica coffee husk tea using flavoromics, targeted screening, and in silico approaches

This study aimed to identify the key volatile compounds in two types of processed arabica coffee husk tea, elucidate their olfactory characteristics, and investigate their antioxidant and anti-inflammatory activities. Sensory evaluation indicated differences between the two groups. A total of 64 and 99 compounds were identified in the C and FC groups, respectively, with 5 identified as key aroma compounds (ROAV≥1). Molecular simulations indicated that four common key aroma compounds were successfully docked with OR1A1 and OR5M3 receptors, forming stable complexes. Furthermore, 14 volatile compounds interacted with 140 targets associated with oxidation and inflammation, linking to 919 gene ontology (GO) terms and 135 kyoto encyclopedia of genes and genomes (KEGG) pathways. Molecular simulations revealed that these volatile components showed antioxidant and anti-inflammatory effects by interacting with core receptors through several forces, including van der Waals, Pi-alkyl, and Pi-cation interactions and hydrogen bonds.

Dynamic changes in quality and flavor compounds of pork tendons during puffing process

To improve the portability of dried pork tendons for consumption, this study investigated the effects of different puffing temperatures (190 °C - 250 °C) and times (1-7 min) on the quality and flavor of pork tendons. As the temperature and time increased, the expansion ratio of pork tendons exhibited a gradual increase. The microstructure of the puffed pork tendons exhibited a uniform porous structure at 230 °C and 250 °C for 6 min. However, further puffing treatment destroyed the spatial structure. GC-IMS identified 68 volatile organic compounds (VOCs), and a total of 16 key VOCs including 2-trans-4-trans-decadienal were screened by GC-MS. Nonanal, 1-octen-3-ol, 2-amylfuran and 2-ethylfuran proved to have a significant effect on the flavor of the puffed pork tendon. The combined puffing performance and flavor analysis revealed that puffing at 230 °C for 6 min was the preferred parameter for puffed pork tendons.

Analysis of volatile flavor compounds in Antarctic krill paste with different processing methods based on GC-IMS

In this study, shrimp paste was prepared using Antarctic krill and fermented Antarctic krill shrimp paste as raw materials. Two commonly used heating methods, stir-fried and steaming, were analyzed, the main difference between the two methods being that stir-frying involves putting the shrimp paste into a wok and stir-frying it for different periods of time, while steaming involves putting the shrimp paste into a steamer and steaming it for different periods of time. The effects of different salt concentrations and processing techniques on the volatile flavor compounds of shrimp paste were also observed. Electronic nose and gas chromatography-ion mobility spectrometry (GC-IMS) were employed to analyze the volatile flavor compounds. A total of 52 volatile flavor compounds were detected by GC-IMS, of which 38 were identified (including monomers, dimers, and polymers). The identified compounds included 11 aldehydes, 6 ketones, 14 alcohols, 2 esters, 2 acids, 1 pyridine compound, and 2 sulfur compounds. In addition, 14 compounds were identifiable. Using the results of the electronic nose analysis, we were also able to differentiate between the volatile flavor compounds in shrimp pastes produced by different processing methods.

Advantages of UHT in retaining coconut milk aroma and insights into thermal changes of aroma compounds

Coconut milk products are susceptible to bacterial damage, necessitating sterilization methods that often compromise nutrient and aroma integrity. This study investigates the effects of different thermal sterilisation methods on coconut milk aroma using headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). We assessed the impact of pasteurisation (PAS, 70 °C, 25 min), high-temperature sterilisation (HTS, 121.1 °C, 15 min), and ultra-high temperature sterilisation (UHT, 130 °C, 5 s) through clustered heat maps and correlation analyses. Significant differences were observed (p < 0.05), with 37 and 52 substances detected by HS-GC-IMS and HS-SPME-GC-MS, respectively, identifying 12 key aroma compounds. UHT treatment primarily reduced 8 acids, maintaining a compositional structure and sensory profile similar to raw coconut milk. PAS and HTS treatments decreased the sensory intensity of overall coconut milk aroma, creamy, and floral notes, correlating with the presence of 2-heptanol, nonanal, 4-methylvaleric acid, and 2-tridecanone. These methods increased cooked notes, associated with 5-methyl-3-heptanone, 3-butyn-1-ol, hydroxyacetone, and acetoin. Rancidity was linked to acids such as isobutyric acid, isovaleric acid, and heptanoic acid, with high temperatures effectively reducing these compounds. Prolonged temperature changes in PAS and HTS accelerated lipid oxidative degradation and the Maillard reaction, involving free fatty acids in the formation of alcohols, aldehydes, esters, and lactones. These findings provide a theoretical basis for studying coconut milk flavour deterioration.

Change in volatile profiles of wheat flour during maturation

The volatile profiles of wheat flour during maturation were examined through headspace solid-phase micro-extraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) combined with electronic nose (E-nose) and electronic tongue (E-tongue) analyses. The wheat flour underwent maturation under three distinct conditions for predetermined durations. While GC/MS coupled with E-tongue exhibited discernment capability among wheat flour samples subjected to varying maturation conditions, E-nose analysis solely relying on principal component analysis failed to achieve discrimination. 83 volatile compounds were identified in wheat flour, with the highest abundance observed in samples matured for 50 d at 25 °C. Notably, trans-2-Nonenal, decanal, and nonanal were the main contributors to the characteristic flavor profile of wheat flour. Integration of HS-SPME-GC/MS with E-tongue indicated superior flavor development and practical viability in wheat flour matured for 50 d at 25 °C. This study furnishes a theoretical groundwork for enhancing the flavor profiles of wheat flour and its derivative products.

Effects of 'bask in sunlight and dewed at night' on the formation of fermented flavor in shrimp paste after maturation

The purpose of the study was to illustrate the roles of three primary indexes, namely sunlight, ventilation and stirring, in the 'bask in sunlight and dewed at night' technique on the quality of shrimp paste, through a laboratory-scale design. The results showed that changes in the post-ripening fermentation conditions, especially sunlight, was instrumental in the physicochemical properties of the shrimp paste. E-nose and SPME-GC-MS were employed to assess the volatile flavor of post-ripening fermentation. A total of 29 key volatile aroma components played a crucial role in the development of post-ripening flavor in shrimp paste with or without sunlight. Lipidomic analysis revealed that sunlight promoted the oxidative degradation of FA, resulting in the production of a diverse range of flavor compounds that imparted the unique aroma of shrimp paste. The findings of this study will establish a theoretical basic for better control of the post-ripening fermentation of traditional shrimp paste.

Characterization of volatile organic compounds in walnut oil with various oxidation levels using olfactory analysis and HS-SPME-GC/MS

Walnut oil oxidizes and becomes rancid during storage, that could be significantly affecting flavor and quality. This study aimed to monitor the volatile compounds present in walnut oil during storage, identify the characteristic markers of walnut oil at different oxidation levels, and establish a correlation network analysis based on the relationship between the olfactory analyzer and the characteristic markers to understand their correlation. The results indicated that the oxidation level of walnut oil had a positive correlation with the response of the olfactory analyzer. 219 volatile compounds were identified in walnut oil, with 89 identified as key volatile compounds (VIP >1). Among these, compounds such as (E, E)-2,4-decadienal (6.10%-23.04%)，(E, E)-2,4-heptadienal (2.23%-13.61%)，(E)-2-octenal (0.95%-11.71%)， hexanoic acid (1.63%-4.30%)，1-octen-3-ol (2.53%-19.01%)，(Z)-2-heptenal (5.95%-25.01%)，2,3-dihydro-furan (1.08%-3.20%)，2-pentyl-furan (0.13%-0.54%), pyrazine (0.33%-1.32%), hexanal (24.52%-1.33%)，3-hethylbutylacetate (12.44%-1.29%)， 2-methyl butyl acetate (7.74%-1.56%) and ethenyl hexanoate (4.39%-0.41%) were found to be characteristic volatile compounds in the oxidation process of walnut oil. Furthermore, the correlation network analysis revealed a strong correlation between the olfactory analyzer sensors and the characteristic volatile compounds. The findings of this study can provide valuable data for the development of rapid determination of the oxidation level of walnut oil.

Characterization of the flavor profile and dynamic changes in Chinese traditional fish sauce (Yu-lu) based on electronic nose, SPME-GC-MS and HS-GC-IMS

In this study, flavor characteristics and dynamic change of Chinese traditional fermented fish sauce (Yu-lu) with different fermentation time (2, 4, 6, 8, and 12 months) were analyzed. The electronic nose analyses confirmed a notable flavor change in fish sauce samples from different stages. During the 12-months fermentation, the total volatile compounds in fish sauce increased from 3.9 mg/L to 13.53 mg/L. Acids, aldehydes, esters and phenols were the main aroma substances and their contents gradually increased during the fermentation process. The PCA of GC-MS and GC-IMS showed that fish sauce samples from different fermentation periods can be well distinguished. A total of 110 volatile compounds identified by GC-MS, and 102 volatile compounds were detected by GC-IMS. Among them, 13 compounds were identified by both GC-MS and GC-IMS. The most varieties (49) of volatiles appeared after 8 months of fermentation. The odor activity value (OAV) analysis showed that 10 volatile compounds were considered as characteristic flavor in traditional fish sauce. The variable influence on projections (VIPs) in PLS-DA models constructed by GC-MS and GC-IMS identified 5 and 10 volatile compounds as biomarkers, respectively. Our results revealed the dynamic changes of characteristic flavor in fish sauce in combination of GC-MS and GC-IMS, which provides theoretical basis for the production and flavor regulation of fish sauce.

Effect of Corynebacterium glutamicum Fermentation on the Volatile Flavors of the Enzymatic Hydrolysate of Soybean Protein Isolate

This study focused on improving the flavor quality of seasonings, and enzymatic hydrolysis of soybean protein isolate (SPI) seasoning via traditional technology may lead to undesirable flavors. Herein, we aimed to develop a new type of SPI seasoning through microbial fermentation to improve its flavor quality. The effect of Corynebacterium glutamicum fermentation on the flavoring compounds of seasonings in SPI enzymatic hydrolysate was examined. Sensory evaluation showed that the SPI seasoning had mainly aromatic and roasted flavor, and the response signals of S18 (aromatic compounds), S24 (alcohols and aldehydes), and S25 (esters and ketones) sensors of the electronic nose differed significantly. Overall, 91 volatile compounds were identified via gas chromatography-mass spectrometry. SPI seasonings contained a higher number of alcohols, ketones, aromatics, and heterocyclic compounds than traditional seasonings, which had stronger cheese, fatty, and roasted aromas. According to the relative odor activity value (ROAV) analysis, n-pentylpyrzine, 2,6-dimethylpyrazine, and tetramethylpyrazine are the key flavoring compounds (ROAV ≥ 1) of SPI seasoning, which may impart a unique roasted and meaty aroma. Therefore, the fermentation of SPI enzymatic hydrolysate with C. glutamicum may improve the flavor quality of its products, providing a new method for the development and production of new seasoning products.

The difference analysis of physicochemical indexes and volatile flavor compounds of chili oil prepared from different varieties of chili pepper

Because of its peculiar flavor, chili oil is widely used in all kinds of food and is welcomed by people. Chili pepper is an important raw material affecting its quality, and commercial chili oil needs to meet various production needs, so it needs to be made with different chili peppers. However, the current compounding method mainly relies on the experience of professionals and lacks the basis of objective numerical analysis. In this study, the chroma and capsaicinoids of different chili oils were analyzed, and then the volatile components were determined by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-ion migration spectrometer (GC-IMS) and electronic nose (E-nose). The results showed that Zidantou chili oil had the highest L*, b*, and color intensity (ΔE) (52.76 ± 0.52, 88.72 ± 0.89, and 118.84 ± 1.14), but the color was tended to be greenyellow. Xinyidai chili oil had the highest a* (65.04 ± 0.2). But its b* and L* were relatively low (76.17 ± 0.29 and 45.41 ± 0.16), and the oil was dark red. For capsaicinoids, Xiaomila chili oil had the highest content of capsaicinoids was 2.68 ± 0.07 g/kg, Tianjiao chili oil had the lowest content of capsaicinoids was 0.0044 ± 0.0044 g/kg. Besides, 96 and 54 volatile flavor substances were identified by GC-MS and GC-IMS respectively. And the main volatile flavor substances of chili oil were aldehydes, alcohols, ketones, and esters. A total of 11 key flavor compounds were screened by the relative odor activity value (ROAV). Moguijiao chili oil and Zidantou chili oil had a prominent grass aroma because of hexanal, while Shizhuhong chili oil, Denglongjiao chili oil, Erjingtiao chili oil, and Zhoujiao chili oil had a prominent floral aroma because of 2, 3-butanediol. Chili oils could be well divided into 3 groups by the partial least squares discriminant analysis (PLS-DA). According to the above results, the 10 kinds of chili oil had their own characteristics in color, capsaicinoids and flavor. Based on quantitative physicochemical indicators and flavor substances, the theoretical basis for the compounding of chili oil could be provided to meet the production demand more scientifically and accurately.

Determination of key volatile fishy substances of sea cucumber powder during the processing and their removal by supercritical fluid extraction

More than 40 volatile compounds were detected in sea cucumber powder during the processing (through freeze-dried, desalination, supercritical fluid extraction and ultra-micro grinding) by multiple methods including e-nose, GC-IMS and GC-MS. It has been determined that aldehydes are the predominant volatile substances in the original freeze-dried sample, accounting for about 30 % of the total volatile substances. In addition, we established a supercritical fluid extraction strategy that could efficiently remove the aldehydes from the sea cucumber powder. GC-IMS and GC-MS showed that the relative content of aldehydes significantly decreased by 14 % and 28 %, respectively. Quantification of aldehydes using GC-MS showed a significant decrease in octanal from 927 µg/kg to 159 µg/kg. Further investigation combined with OAV analysis showed that 17 volatile substances in the freeze-dried sea cucumber powder were considered to be the predominant volatile compounds (OAV > 1).The primary fishy compounds found in sea cucumber powder were identified as hexanal, octanal, and an unidentified compound using GC-O, which can be effectively removed (OAV can't been estimated) by the supercritical fluid extraction strategy we established.

Multiple analyses of main flavor components in reconstituted tobacco and transfer behavior of their key substances during heating

Reconstituted tobacco (RT) is a product made by reprocessing tobacco waste, experiencing a growing demand for heat-not-burn products. The purpose of this study is to analyze the main flavor ingredients in RT aerosol, as well as the transfer behavior of key flavor substances from substrates to aerosol and the concentrations of these compounds in the substrate after heating. First, we demonstrated that the odor of four RT aerosol samples could be distinguished using an electronic nose. Through non-targeted analysis, 93 volatile compounds were detected by gas chromatography-mass spectrometry, and 286 non/semi-volatile compounds were identified by ultra-high-performance liquid electrophoresis chromatography-mass spectrometry in aerosol. Furthermore, we found that the formation of RT aerosol involves primarily evaporation and distillation, however, the total content delivered from unheated RT samples to aerosol remains relatively low due to compound volatility and cigarette filtration. Thermal reactions during heating indicated the pyrolysis of chlorogenic acid to generate catechol and resorcinol, while Maillard reactions involving glucose and proline produced 2,3-dihydro-3,5-dihydroxy-6-methyl-4h-pyran-4-one. The study highlighted that heating RT at approximately 300°C could mitigate the production of harmful substances while still providing a familiar sensory experience with combusted tobacco.

Comparative Analysis of Texture Characteristics, Sensory Properties, and Volatile Components in Four Types of Marinated Tofu

In this study, three different brands of commercially available marinated tofu were analyzed and compared with homemade products to explore the effect of key flavor substances on their sensory quality, sensory properties, texture characteristics, and volatile components. The texture characteristics and flavor substances of the three brands of commercially available marinated tofu were significantly different from those of homemade products. A total of 64 volatile components were identified by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), mainly including 11 hydrocarbons, 11 alcohols, 10 ketones, 15 aldehydes, 4 esters, 1 acid, and 12 other volatile substances. Among these, nine key flavor compounds (ROAV > 1, VIP > 1) were identified using the relative odor activity value (ROAV) combined with a partial least squares discriminant analysis (PLS-DA) and variable importance in projection, including α-Pinene, β-Myrcene, α-Phellandrene, 1-Penten-3-one, Butanal, 3-Methyl butanal, acetic acid ethyl ester, 1,8-Cineol, and 2-Pentyl furan. The correlation heatmap showed that sensory evaluation was positively correlated with hardness, gumminess, chewiness, and springiness while negatively correlated with 2-Pentyl furan, α-Pinene, resilience, α-Phellandrene, 1-Penten-3-one, acetic acid ethyl ester, and 1,8-Cineol. Overall, this study provides a theoretical reference for developing new instant marinated tofu snacks.

Study on the quality of soybean proteins fermented by Bacillus subtilis BSNK-5: Insights into nutritional, functional, safety, and flavor properties

Microbial fermentation emerges as a promising strategy to elevate the quality of soybean proteins in food industry. This study conducted a comprehensive assessment of the biotransformation of four types of soybean proteins by Bacillus subtilis BSNK-5, a proteinase-rich bacterium. BSNK-5 had good adaptability to each protein. Soluble protein, peptides and free amino acids increased in fermented soybean proteins (FSPs) and dominant after 48-84 h fermentation, enhancing nutritional value. Extensive proteolysis of BSNK-5 also improved antioxidant and antihypertensive activities, reaching peak level after 48 h fermentation. Furthermore, excessive proteolysis effectively enhanced the generation of beneficial spermidine without producing toxic histamine after fermentation, and formed the flavor profile with 56 volatiles in 48 h FSPs. Further degradation of amino acids showed a positive correlation with off-flavors, particularly the enrichment of 3-methylbutanoic acid. These findings establish a theoretical foundation for regulating moderate fermentation by BSNK-5 to enabling the high-value utilization of soybean protein.

Solid-phase microextraction - a future technique in pharmacology and coating trends

Traditional sample preparation techniques based on liquid-liquid extraction (LLE) or solid-phase extraction (SPE) often suffer from a major error due to the matrix effects caused by significant co-extraction of matrix components. The implementation of a modern extraction technique such as solid-phase microextraction (SPME) was aimed at reducing analysis time and the use of organic solvents, as well as eliminating pre-analytical and analytical errors. Solid-phase microextraction (SPME) is an innovative technique for extracting low molecular weight compounds (less than 1500 Da) from highly complex matrices, including biological matrices. It has a wide range of applications in various types of analysis including pharmaceutical, clinical, metabolomics and proteomics. SPME has a number of advantages over other extraction techniques. Among the most important are low environmental impact, the ability to sample and preconcentrate analytes in one step, simple automation, and the ability to extract multiple analytes simultaneously. It is expected to become, in the future, another method for cell cycle research. Numerous available literature sources prove that solid-phase microextraction can be a future technique in many scientific fields, including pharmaceutical sciences. This paper provides a literature review of trends in SPME coatings and pharmacological applications.

Characterization of the key flavor compounds in cream cheese by GC-MS, GC-IMS, sensory analysis and multivariable statistics

The aroma types of cream cheese affect its commercial value and consumer acceptability. However, the types of volatile substances and sensory characteristics of cream cheese at different fermentation stages are still unclear. Therefore, in this study, headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) were used to analyze the volatile substances in cream cheese fermentation. Orthogonal partial least squares discriminant analysis (OPLS-DA), odor activity value (OAV), relative odor activity value (ROAV) and variable projection importance (VIP) were used to identify the characteristic flavor substances in cream cheese fermentation. Finally, the relationship between key flavor substances and sensory characteristics was determined by partial least squares (PLS) analysis. A total of 34 and 36 volatile organic compounds were identified by HS-SPME-GC-MS and HS-GC-MS, respectively, and 14 characteristic flavor substances were found, based on VIP, ROAV and OAV models. Combined with sensory analysis and flavor substance changes, it was found that the cream cheese fermented for 15 d had the best flavor and taste. This study reveals the characteristics and contribution of volatile substances in cream cheese at different fermentation stages, which provides new insights into improving flavor and quality control.

Impact of aroma-enhancing microorganisms on aroma attributes of industrial Douchi: An integrated analysis using E-nose, GC-IMS, GC-MS, and descriptive sensory evaluation

In order to enhance the aromatic profile of industrial Douchi, a comprehensive investigation was undertaken to assess the impact of aroma-enhancing microorganisms on the sensory attributes of Douchi. This evaluation utilized a combination of analytical techniques, including electronic nose analysis, gas chromatography-ion mobility spectrometry (GC-IMS), gas chromatography-mass spectrometry (GC-MS), and descriptive sensory analysis (DA). Both GC-IMS and GC-MS revealed significant changes in the volatile composition of Douchi following the addition of aroma-enhancing microorganisms (p < 0.05). Partial least squares-discriminant analysis (PLS-DA) identified benzaldehyde, benzene acetaldehyde, 3-octanone, and ethyl 2-methylbutyrate as significant differentiating volatile compounds. Additionally, compared to the control group, the sensory attributes of sourness in Douchi were significantly reduced (p < 0.001), while the attributes of wine-like and sweetness were notably enhanced (p < 0.05) when the ratio of G. candidum to C. versatilis was 1:1 (GCC group). By calculating the odor-activity values (OAVs) of key volatiles, it can be hypothesized that this aroma improvement of Douchi may be attributed to an increase in the typical volatiles (3-methyl-1-butanol, 1-octen-3-ol, 3-octanol, and 3-octanone) and ethyl 2-methylbutanoate with high OAVs (2340849.64 ∼ 16695327.86), as well as to decreases in the musty acetophenone. In conclusion, the aroma profile of Douchi was significantly enhanced when G. candidum and C. versatilis were added at a ratio of 1:1. This study provides valuable insights into the development of aroma enhancers for improving the sensory profile of Douchi.

Analysis of changes in volatile compounds and evolution in free fatty acids, free amino acids, nucleotides, and microbial diversity in tilapia (Oreochromis mossambicus) fillets during cold storage

BACKGROUND

Aquatic products are rich in nutrients and unique in flavor, and are popular among the public. However, aquatic products are extremely susceptible to quality degradation during storage, of which odor deterioration is the most obvious and influential aspect. Odor deterioration in aquatic products is widespread and severely affects overall flavor and quality. In this study, odor deterioration and flavor-related quality degradation of tilapia during cold storage are discussed, focusing on the changes in volatile compounds and the evolution of free fatty acids (FFAs), free amino acids (FAAs), nucleotides, and microbial diversity.

RESULTS

A total of 63 volatile compounds were detected by gas chromatography-mass spectrometry, including 11 hydrocarbons, 10 alcohols, 6 aldehydes, 8 ketones, 6 esters, 9 aromatics, 3 phenols, and 10 other compounds. Microbial diversity analysis revealed that Acinetobacter, Psychrobacter, Vagococcus, and Myroides were the main dominant species of tilapia at the end of cold storage and predicted that microorganisms could influence the flavor of tilapia by participating in important metabolic pathways. Meanwhile, the evolution of FFAs, FAAs, and nucleotides also had a significant impact on odor deterioration, as evidenced by the contribution of unsaturated fatty acids (such as oleic acid and linoleic acid), Lys, and off-flavor nucleotides (HxR and Hx) to the undesirable flavor. Oxidation of oleic acid and linoleic acid resulted in changes in aldehydes, with Lys, HxR, and Hx being key flavor precursors and off-flavor contributors.

CONCLUSION

This study contributes to a comprehensive overview of odor deterioration and the evolution of flavor-related quality in tilapia during cold storage, providing new insights into the regulation of overall flavor and quality. © 2023 Society of Chemical Industry.

Changes in Flavor-Related Biomarkers in Pacific Oysters (Crassostrea gigas) Following Microplastic Exposure

Microplastics have been an emerging threat to filtering species and the ingestion and impacts of microplastics on oysters are a cause for concern. However, much remains unknown about the effects of microplastics on flavor-related biomarkers in oysters. Herein, a laboratory microplastic exposure with concentrations of 1, 10, and 100 mg/L for 15 days was performed to investigate the impacts of microplastics on the flavor parameters of oysters. Exposure to microplastics changed the odor characteristics of oysters. Microplastic exposure had minor effects on the fatty acid composition; however, significant alterations in free amino acids and nucleotides were observed under the 1 and 10 mg/L exposure groups, respectively. The overall results indicated 10 mg/L of microplastic exposure significantly increased the equivalent umami value of oysters. These findings stressed the effects of microplastics on oysters and would be an important reference for the assessment of the potential risks associated with microplastics in marine edible species.

Airborne microorganisms and key environmental factors shaping their community patterns in the core production area of the Maotai-flavor Baijiu

Airborne microorganisms are important parts of the Moutai-flavor Baijiu brewing microbial community, which directly affects the quality of Baijiu. However, environmental factors usually shape airborne microbiomes in different distilleries, even in the different production areas of the same distillery. Unfortunately, current understanding of environmental factors shaping airborne microbiomes in distilleries is very limited. To bridge this gap, we compared airborne microbiomes in the Moutai-flavor Baijiu core production areas of different distilleries in the Chishui River Basin and systematically investigated the key environmental factors that shape the airborne microbiomes. The top abundant bacterial communities are mainly affiliated to the phyla Actinobacteriota, Firmicutes, and Proteobacteri, whereas Ascomycota and Basidiomycota are the predominant fungal communities. The Random Forest analysis indicated that the biomarkers in three distilleries are Saccharomonospora and Bacillus, Thermoactinomyces, Oceanobacillus, and Methylobacterium, which are the core functional flora contributing to the production of Daqu. The correlation and network analyses showed that the distillery age and environmental temperature have a strong regulatory effect on airborne microbiomes, suggesting that the fermentation environment has a domesticating effect on air microbiomes. Our findings will greatly help us understand the relationship between airborne microbiomes and environmental factors in distilleries and support the production of the high-quality Moutai-flavor Baijiu.

Effects of freezing methods on physicochemical properties, protein/fat oxidation and odor characteristics of surimi gels with different cross-linking degrees

This work investigated the effects of liquid nitrogen immersion freezing (LNF), -35 °C air freezing (AF-35℃) and -18 °C air freezing (AF-18℃) on the physical and chemical characteristics and flavor quality of surimi gels with different cross-linking degrees. Compared to AF-35 °C and AF-18 °C, LNF was shown to considerably delay the texture deterioration and water migration of frozen gels, as well as the accumulation of thiobarbituric acid reactive substance values and carbonyl contents. Additionally, an appropriate increase of cross-linking degree (45.83 to 62.99%) was found able to improve gel properties and inhibit quality deterioration during freezing. Moreover, LNF-treated gels were closer to fresh gels in the amount of volatile compounds, in contrast to most significant negative aroma changes in AF-18℃-treated gels. Furthermore, 29, 29 and 31 key differential volatile compounds were screened for gels with a cross-linking degree of 29.66, 45.83 and 62.99%, respectively, mainly including aldehydes, alcohols and esters.

A Systematic Comparative Study on the Physicochemical Properties, Volatile Compounds, and Biological Activity of Typical Fermented Soy Foods

Fermented soy foods can effectively improve the unpleasant odor of soybean and reduce its anti-nutritional factors while forming aromatic and bioactive compounds. However, a differential analysis of characteristic flavor and function among different fermented soy foods has yet to be conducted. In this study, a systematic comparison of different fermented soy foods was performed using E-nose, HS-SMPE-GC×GC-MS, bioactivity validation, and correlation analysis. The results showed that soy sauce and natto flavor profiles significantly differed from other products. Esters and alcohols were the main volatile substances in furu, broad bean paste, douchi, doujiang, and soy sauce, while pyrazine substances were mainly present in natto. Phenylacetaldehyde contributed to the sweet aroma of furu, while 1-octene-3-ol played a crucial role in the flavor formation of broad bean paste. 2,3-Butanediol and ethyl phenylacetate contributed fruity and honey-like aromas to douchi, doujiang, and soy sauce, respectively, while benzaldehyde played a vital role in the flavor synthesis of douchi. All six fermented soy foods demonstrated favorable antioxidative and antibacterial activities, although their efficacy varied significantly. This study lays the foundation for elucidating the mechanisms of flavor and functionality formation in fermented soy foods, which will help in the targeted development and optimization of these products.

Effect of Freeze-Thaw Cycles on the Freshness of Prepackaged Penaeus vannamei

The effect of temperature fluctuations on the freshness of shrimp in simulated trays was investigated by setting a freeze-thaw (F-T) cycle of 12 h after freezing at -20 °C and thawing at 1 °C under refrigeration. The results showed that the shrimp's physicochemical properties deteriorated to different extents with the increase in F-T cycles. The total colony count of shrimp was 6.07 lg CFU/g after 21 cycles, and the volatile saline nitrogen content reached 30.36 mg/100 g, which exceeded the edible standard. In addition, the sensory quality and textural properties (hardness, elasticity, chewiness, and adhesion) declined to different degrees with increased F-T cycles. LF-NMR and protein property measurements showed that F-T cycles resulted in reduced water holding capacity and protein denaturation, which were the main factors leading to the deterioration of shrimp quality. Furthermore, flavor changes were analyzed using an electronic nose sensor to establish a freshness model. The W1W, W1S, W2S, and W5S sensors were correlated with the quality changes in shrimp and used as the main sensors for detecting the freshness of Penaeus vannamei. As a result, to better maintain the overall freshness, temperature fluctuations should be minimized in sales and storage, and fewer than 8 F-T cycles should be performed.

Integrated characterization of filler tobacco leaves: HS-SPME-GC-MS, E-nose, and microbiome analysis across different origins

This study delves into the aroma characteristics and microbial composition of filler tobacco leaves (FTLs) sourced from six distinct cigar-growing regions within Yunnan, China, following standardized fermentation. An integrated approach using gas chromatography-mass spectrometry (GC-MS), electronic nose (E-nose), and microbiome analysis was employed for comprehensive profiling. Results derived from Linear Discriminant Analysis (LDA) using E-nose data confirmed the presence of notable variability in flavor substance profiles among the FTLs from six regions. Additionally, GC-MS was used to discern disparities in volatile organic compound (VOC) distribution across FTLs from these regions, identifying 92, 81, 79, 58, 69, and 92 VOCs within each respective sample set. Significantly, 24 VOCs emerged as pivotal determinants contributing to the heterogeneity of flavor profiles among FTLs from diverse origins, as indicated by Variable Importance for the Projection (VIP) analysis. Furthermore, distinctions in free amino acid content and chemical constituents were observed across FTLs. Of noteworthy significance, solanone, isophorone, durene, (-)-alpha-terpineol, and 2,3'-bipyridine exhibited the strongest correlations with microbiome data, with fungal microorganisms exerting a more pronounced influence on metabolites, as elucidated through two-way orthogonal partial least-squares (O2PLS) modeling. These findings provide a theoretical and technical basis for accurately evaluating the synchronization of FTLs in aromas and fermentation processes, and they will enhance the quality of fermented FTLs and foster the growth of the domestic cigar tobacco industry ultimately.

Characterization of Volatile Compounds in Donkey Meat by Gas Chromatography-Ion Mobility Spectrometry (GC-IMS) Combined with Chemometrics

Volatile compounds (VOCs) are an important factor affecting meat quality. However, the characteristic VOCs in different parts of donkey meat remain unknown. Accordingly, this study represents a preliminary investigation of VOCs to differentiate between different cuts of donkey meat by using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) combined with chemometrics analysis. The results showed that the 31 VOCs identified in donkey meat, ketones, alcohols, aldehydes, and esters were the predominant categories. A total of 10 VOCs with relative odor activity values ≥1 were found to be characteristic of donkey meat, including pentanone, hexanal, nonanal, octanal, and 3-methylbutanal. The VOC profiles in different parts of donkey meat were well differentiated using three- and two-dimensional fingerprint maps. Nine differential VOCs that represent potential markers to discriminate different parts of donkey meat were identified by chemometrics analysis. These include 2-butanone, 2-pentanone, and 2-heptanone. Thus, the VOC profiles in donkey meat and specific VOCs in different parts of donkey meat were revealed by HS-GC-IMS combined with chemometrics, whcih provided a basis and method of investigating the characteristic VOCs and quality control of donkey meat.

Characterization of key aroma compounds in gray sufu fermented using Leuconostoc mesenteroides subsp. Mesenteroides F24 as a starter culture

Gray sufu is a traditional fermented bean product with strong flavor in China, but traditional fermentation methods often lead to its off-flavor. This study was performed to investigate the flavor quality characteristics of gray sufu fermented using L. mesenteroides F24. Results showed 220 volatile compounds in gray sufu, among which alcohols and esters were the main volatiles. Inoculation with L. mesenteroides F24 considerably affected the contents of flavor substances in gray sufu and substantially increased the main flavor compounds. In addition, 29 kinds of key volatile compounds were identified by analyzing the ROAVs. Four unique key flavor substances were found in gray sufu inoculated with L. mesenteroides F24. This study is the first report on the feasibility of L. mesenteroides F24 as a promising starter culture to improve the flavor quality of gray sufu. The results provide a theoretical basis for improving the processing and quality control of gray sufu.

Correlations between flavor and fermentation days and changes in quality-related physiochemical characteristics of fermented Aurantii Fructus

The effects of different fermentation times (0, 1, 2, 3, 4, and 5 days) on the physicochemical properties and flavor components of fermented Aurantii Fructus (FAF) were evaluated. Component analysis identified 66 compounds in positive ion mode and 32 compounds in negative ion mode. Flash GC e-nose results showed that propanal, (+)-limonene and n-nonanal may be the flavor characteristic components that distinguish FAF with different fermentation days. Furthermore, we found that the change of total flavonoid content was closely related to colony growth vitality. The total flavonoid content of FAF gradually decreased from 3rd day and then increased from 5th day (3rd day: 0.766 ± 0.123 mg/100 g; 4th day: 0.464 ± 0.001 mg/100 g; 5th day: 0.850 ± 0.192 mg/100 g). Finally, according to antioxidant activity correlation analysis, meranzin, (+)-limonene and total flavonoids were found to be the key substances affecting the fermentation days of FAF. Overall, the optimal fermentation time for FAF was 4 days.

Effects of ultrasonic treatment on the structural, functional properties and beany flavor of soy protein isolate: Comparison with traditional thermal treatment

This research explored the influences of ultrasonic and thermal treatments on the structure, functional properties, and beany flavor of soy protein isolate (SPI). In comparison with traditional thermal treatment, ultrasonic treatment effectively induced protein structural unfolding and exposure of hydrophobic groups, which reduced relative content of α-helix, increased relative content of β-turn, β-sheet and random coil, and improved the solubility, emulsifying and foaming properties of SPI. Both treatments significantly decreased the species and contents of flavor compounds, such as hexanal, (E)-2-nonenal, (Z)-2-heptenal and (E)-2-hexenal in SPI. The relative content of hexanal in the major beany flavor compound decreased from 11.69% to 6.13% and 5.99% at 350 W ultrasonic power and 150 s thermal treatment procedure, respectively. After ultrasonic treatment, structural changes in SPI were significantly correlated with functional properties but showed a weak correlation with flavor. Conversely, the opposite trend was observed for thermal treatment. Thus, using ultrasonic treatment to induce and stabilise the denatured state of proteins is feasible to improve the functional properties and beany flavor of SPI.

Suanyu fermentation strains screening, process optimization and the effect of thermal processing methods on its flavor

Suanyu is a famous traditional fermented aquatic food in south China. However, the quality of Suanyu is unstable due to natural fermentation based on the environment. This work screened suitable microbial fermenters (Enterococcus rivorum and Enterococcus lactis) from traditional fermented fish and optimized a suitable fermentation process. Effects of different fermentation (natural and mixed starters fermentation) and thermal treatments (microwave, frying and roasting) on the flavor of Suanyu were investigated. Compared to the natural fermentation group, the TVB-N content (31.5 mg/100 g) was lower, the total acidity (5.12 g/kg) and flavor compounds content were richer in the mixed starters fermentation group (P < 0.05). But there was no significant difference in histamine content (P > 0.05). The roasting treatment group contained higher contents of free amino acids, organic acids, nucleotides and richer key aroma components. The electronic nose was able to distinguish between the differently treated samples. The sensory evaluation result showed that roasted and fried samples had a more acceptable flavor and color. This work will provide a theoretical reference for the standardized production of Suanyu and the development of pre-cooked products.

Uncovering the differences in flavor volatiles of different colored foxtail millets based on gas chromatography-ion migration spectrometry and chemometrics

The differences of volatile organic compounds in commercially available foxtail millets with different colors (black, green, white and yellow) were assayed through gas chromatography-ion migration spectrometry (GC-IMS) to explore their volatile flavor characteristics. Fifty-five volatile components were found in various colored foxtail millets, including 25 kinds of aldehydes (accounting for 39.19-48.69%), 10 ketones (25.36-32.37%), 15 alcohols (20.19-24.11%), 2 ethers (2.29-2.45%), 2 furans (1.49-2.95%) and 1 ester (0.27-0.39%). Aldehydes, alcohols and ketones were the chief volatiles in different colored foxtail millet, followed by furans, esters and ethers. These identified volatile flavor components in various colored foxtail millets obtained by GC-IMS could be well distinguished by principal components and cluster analysis. Meanwhile, a stable prediction model was fitted via partial least squares-discriminant analysis (PLS-DA), in which 17 kinds of differentially volatile components were screened out based on variable importance in projection (VIP>1). These findings might provide certain information for understanding the flavor traits of colored foxtail millets in future.

Characterization and discrimination of flavor volatiles of different colored wheat grains after cooking based on GC-IMS and chemometrics

Changes in flavor volatiles of three colored wheat grains (black, green, and yellow) after cooking were detected via gas chromatography-ion migration spectrometry (GC-IMS) to explore corresponding volatile flavor traits. A total of 52 volatile chemicals were spotted among these cooked wheat grains, including 30 aldehydes (accounting for 73.86-83.78%), 11 ketones (9.53-16.98%), 3 alcohols (0.88-1.21%), 4 furans (4.82-7.44%), 2 esters (0.28-0.42%), and 2 pyrazines (0.18-0.32%). Aldehydes, ketones, and furans were the main volatile compounds in three different cooked wheat. For black-colored wheat, the relative contents of benzene acetaldehyde, benzaldehyde, 2-methyl butanal, and 3-methyl butanal were much higher (p < 0.05). For green-colored wheat, the relative contents of nonanal, 2-pentyl furan, (E)-hept-2-enal, 2-butanone, and acetone were significantly higher (p < 0.05). For yellow-colored wheat, the relative amounts of heptanal, hexanal, and pentanal were much higher (p < 0.05). The overall volatile substances of the three cooked wheat grains might be classified by GC-IMS data coupled with principal component analysis and heatmap clustering analysis. A reliable forecast set was established through orthogonal partial least squares-discriminant analysis (OPLS-DA), and 22 differential volatile compounds were screened out based on variable importance in projection (VIP) being higher than 1.0, as flavor markers for distinguishing the three cooked wheat grains. These results suggest that GC-IMS could be used for characterizing the flavor volatiles of different colored wheat, and the findings could contribute certain information for understand the aroma traits in different colored cooked wheat and related products in the future.

Flavor Formation in Dry-Cured Fish: Regulation by Microbial Communities and Endogenous Enzymes

Dried salted fish is a traditional dry-cured fish that is sprinkled with salt before the curing process. With a unique flavor as well as diverse varieties, dry-cured fish is popular among consumers worldwide. The presence of various microbial communities during the curing process leads to numerous metabolic reactions, especially lipid oxidation and protein degradation, which influence the formation of flavor substances. However, during industrial curing, the quality of dry-cured fish is difficult to control, leading to the formation of products with diverse flavors. This review describes the curing process of dried salted fish, the key microorganisms involved in the curing process of typical dried salted fish products at home and abroad, and the correlation between biological metabolism and flavor formation and the underlying mechanism. This review also investigates the prospects of dried salted fish products, proposing methods for the analysis of improved curing processes and the mechanisms of dried salted fish. Through a comprehensive understanding of this review, modern production challenges can be addressed to achieve greater control of microbial growth in the system and improved product safety. In addition to advancing our understanding of the processes by which volatile flavor compounds are formed in conventional dry-cured fish products, we expect that this work will also offer a theoretical framework for enhancing their flavor in food processing.

Applications, challenges and prospects of bionic nose in rapid perception of volatile organic compounds of food

Bionic nose, a technology that mimics the human olfactory system, has been widely used to assess food quality due to their high sensitivity, low cost, portability and simplicity. This review briefly describes that bionic noses with multiple transduction mechanisms are developed based on gas molecules' physical properties: electrical conductivity, visible optical absorption, and mass sensing. To enhance their superior sensing performance and meet the growing demand for applications, a range of strategies have been developed, such as peripheral substitutions, molecular backbones, and ligand metals that can finely tune the properties of sensitive materials. In addition, challenges and prospects coexist are covered. Cross-selective receptors of bionic nose will help and guide the selection of the best array for a particular application scenario. It provides an odour-based monitoring tool for rapid, reliable and online assessment of food safety and quality.

Effects of a Novel Starter Culture on Quality Improvement and Putrescine, Cadaverine, and Histamine Inhibition of Fermented Shrimp Paste

Fermented shrimp paste is a popular food in Asian countries. However, biogenic amines (BAs) are a typically associated hazard commonly found during the fermentation of shrimp paste and pose a food-safety danger. In this work, an autochthonic salt-tolerant Tetragenococcus muriaticus TS (T. muriaticus TS) strain was used as a starter culture for grasshopper sub shrimp paste fermentation. It was found that with the starter culture, putrescine, cadaverine, and histamine concentrations were significantly lower (p < 0.05) with a maximal reduction of 19.20%, 14.01%, and 28.62%, respectively. According to high-throughput sequencing data, T. muriaticus TS could change the interactions between species and reduce the abundance of bacterial genera positively associated with BAs, therefore inhibiting the BA accumulation during shrimp paste fermentation. Moreover, the volatile compounds during the fermentation process were also assessed by HS-SPME-GC-MS. With the starter added, the content of pyrazines increased, while the off-odor amines decreased. The odor of the shrimp paste was successfully improved. These results indicate that T. muriaticus TS can be used as an appropriate starter culture for improving the safety and quality of grasshopper sub shrimp paste.

The odor deterioration of tilapia (Oreochromis mossambicus) fillets during cold storage revealed by LC-MS based metabolomics and HS-SPME-GC-MS analysis

Odor deterioration of tilapia during cold storage is unavoidable and affects flavor and quality severely. Odor is characterized by the abundance of volatile compounds and metabolites. In this study, headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and metabolomic analysis were applied to explore the volatile compounds, differential metabolites, and metabolic pathways related to the odor deterioration of tilapia during cold storage. A total of 29 volatile compounds were detected to be associated with the odor deterioration of tilapia. And 485 differential metabolites were screened, of which 386 differential expressions were up-regulated and 99 differential expressions were down-regulated. Three major metabolic pathways including linoleic acid metabolism, alanine, aspartate, glutamate metabolism, and nucleotide metabolism were obtained. A potential metabolic network map was also proposed. This study contributes to revealing the metabolic mechanisms of odor deterioration in tilapia during cold storage and providing a theoretical reference for the regulation of flavor and quality.

Effect of fat replacement by flaxseed flour on the quality parameters of pork meatballs

To improve the edible qualities of meatballs, various percentages of pork fat in meatballs were replaced by brown flaxseed flour (BFF) to decrease the fat contents and further optimize the fatty acid compositions. Five different meatball formulations that used 0%, 5%, 10%, 15%, and 20% of flaxseed flour additions were used in which the corresponding amounts pork fat were replaced. The proximate compositions, water activity, pH levels, colors, textures, cooking losses, fatty acid compositions, sensory properties, flavors, and oxidation stabilities of these meatballs were analyzed. Increasing the BFF addition amounts improved the protein and dietary fiber contents, pH levels, fatty acid profiles and oxidation stabilities, but decreased the fat contents, moisture levels, cooking losses, n6/n3 ratios, hardness, and lightness. The volatile flavors of meatballs with different BFF replacement levels were significantly different. According to the sensory evaluation, the use of 5% BFF increased the odor of meatballs without significantly affecting the other sensory scores. This work demonstrated that BFF may be a healthier alternative as pork fat replacer for preparing meatballs.

A multi-omics-based investigation into the flavor formation mechanisms during the fermentation of traditional Chinese shrimp paste

The fermentation process of traditional shrimp paste is closely associated with the production of flavor substances, but the formation mechanism of key aroma components is still unclear. In this study, a comprehensively flavor profile analysis of traditional fermented shrimp paste was carried out by E-nose and SPME-GC-MS. A total of 17 key volatile aroma components with OAV > 1 contributed greatly to the overall flavor formation of shrimp paste. In addition, high-throughput sequencing (HTS) analysis revealed that Tetragenococcus was the dominant genera in the whole fermentation process. Moreover, metabolomics analysis showed that the oxidation and degradation of lipids, protein, organic acids and amino acids produced a large number of flavor substances and intermediates, which laid the foundation for the Maillard reaction in term of generating the distinct aroma of the traditional shrimp paste. This work will provide theoretical support for the realization of flavor regulation and quality control in traditional fermented foods.

Determining the changes in metabolites of Dendrobium officinale juice fermented with starter cultures containing Saccharomycopsis fibuligera FBKL2.8DCJS1 and Lactobacillus paracasei FBKL1.3028 through untargeted metabolomics

BACKGROUND

The present study aimed to investigate the changes in volatile components and metabolites of Dendrobium officinale (D. officinale) juice fermented with starter cultures containing Saccharomycopsis fibuligera and Lactobacillus paracasei at 28 ℃ for 15 days and post-ripened at 4 ℃ for 30 days using untargeted metabolomics of liquid chromatography-mass spectrometry (LC-MS) and headspace solid-phase microextraction-gas chromatography (HS-SPME-GC-MS) before and after fermentation.

RESULTS

The results showed that the alcohol contents in the S. fibuligera group before fermentation and after fermentation were 444.806 ± 10.310 μg/mL and 510.999 ± 38.431 μg/mL, respectively. Furthermore, the alcohol content in the fermentation broth group inoculated with the co-culture of L. paracasei + S. fibuligera was 504.758 ± 77.914 μg/mL, containing a significant amount of 3-Methyl-1-butanol, Linalool, Phenylethyl alcohol, and 2-Methyl-1-propanol. Moreover, the Ethyl L (-)-lactate content was higher in the co-culture of L. paracasei + S. fibuligera group (7.718 ± 6.668 μg/mL) than in the L. paracasei (2.798 ± 0.443 μg/mL) and S. fibuligera monoculture groups (0 μg/mL). The co-culture of L. paracasei + S. fibuligera significantly promoted the metabolic production of ethyl L (-)-lactate in D. officinale juice. The differential metabolites screened after fermentation mainly included alcohols, organic acids, amino acids, nucleic acids, and their derivatives. Twenty-three metabolites, including 11 types of acids, were significantly up-regulated in the ten key metabolic pathways of the co-culture group. Furthermore, the metabolic pathways, such as pentose and glucuronate interconversions, the biosynthesis of alkaloids derived from terpenoid and polyketide, and aminobenzoate degradation were significantly up-regulated in the co-culture group. These three metabolic pathways facilitate the synthesis of bioactive substances, such as terpenoids, polyketides, and phenols, and enrich the flavor composition of D. officinale juice.

CONCLUSIONS

These results demonstrate that the co-culture of L. paracasei + S. fibuligera can promote the flavor harmonization of fermented products. Therefore, this study provides a theoretical basis for analyzing the flavor of D. officinale juice and the functional investigation of fermentation metabolites.

Characterization of physical properties, volatile compounds and aroma profiles of different salted egg yolk lipids

Salted egg yolks (SEY) have a desirable and unique flavor with multiple underlying applications in food processing, and their abundant lipids contribute to a creamy and pleasant aroma. However, it is important to maintain the stability of the SEY flavor, which depends to a large extent on the egg species and the processing method. This study aimed to extract different SEY lipids with conventional solvents, analyze the fatty acid composition, and screen the volatile compounds to elucidate the flavor differences between salted hen eggs and duck eggs. Compared to ethanol extraction, acetone-extracted lipids had lower acid value and viscosity, and almost had no phospholipid content. Fatty acid analysis revealed that the highest content of fatty acid in SEY lipids was oleic acid, followed by palmitic acid and linoleic acid, while there were significant variations of different SEY lipids in the fatty acid profiles. The volatile compounds were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and the overall odor was detected by the electronic nose (E-nose). A total of 27 volatile compounds were analyzed in SEY lipids and divided into 8 chemical classes. The aldehydes, furans and pyrazines were decreased, and the hydrocarbons were increased compared with untreated SEY. The combination of the physical properties and flavor evaluation of SEY lipids could provide a theoretical basis for the extension of the characteristic flavor matrix in SEY.

Characterization of non-volatile and volatile flavor profiles of Coregonus peled meat cooked by different methods

This study investigated the effects of different cooking methods on non-volatile flavor (free amino acids, 5'-nucleotides, and organic acids, etc.) of Coregonus peled meat. The volatile flavor characteristics were also analyzed by electric nose and gas chromatography-ion migration spectrometry (GC-IMS). The results indicated that the content of flavor substances in C. peled meat varied significantly. The electronic tongue results indicated that the richness and umami aftertaste of roasting were significantly greater. The content of sweet free amino acids, 5'-nucleotides, and organic acids was also higher in roasting group. Electronic nose principal component analysis can distinguish C. peled meat cooked (the first two components accounted for 98.50% and 0.97%, respectively). A total of 36 volatile flavor compounds were identified among different groups, including 16 aldehydes, 7 olefine aldehydes, 6 alcohols, 4 ketones, and 3 furans. In general, roasting was recommended and gave more flavor substances in C. peled meat.

Characterization of the Key Aroma Volatile Compounds in Nine Different Grape Varieties Wine by Headspace Gas Chromatography-Ion Mobility Spectrometry (HS-GC-IMS), Odor Activity Values (OAV) and Sensory Analysis

During this study, the physicochemical properties, color, and volatile aroma compounds of the original wines produced from the grape varieties ‘Hassan’, ‘Zuoshaner’, ‘Beibinghong’, ‘Zuoyouhong’, ‘Beta’, ‘Shuanghong’, ‘Zijingganlu’, ‘Cabernet Sauvignon’, and ‘Syrah’ were determined and sensory evaluation was performed. Results indicated that ‘Hassan’ contained the most solids, ‘Zuoshaner’ produced the most total acid, residual sugar, total anthocyanin, and total phenol, and ‘Shuanghong’ produced the most tannin. Calculation of the chroma and hue of the wines according to the CIEL*a*b* parameters revealed that the ‘Cabernet Sauvignon’ wines were the brightest of the nine varieties and that the ‘Zuoshaner’ wines had the greatest red hue and yellow hue and the greatest saturation’. A total of 52 volatile compounds were identified and quantified in nine wine samples by HS-GC-IMS analysis, with the most significant number of species detected being 20 esters, followed by 16 alcohols, 8 aldehydes, four ketones, one terpene, and one furan, with the highest total volatile compound content being ‘Beta’. A total of 14 volatile components with OAV (odor activity value) >1 were calculated using the odor activity value (OAV) of the threshold of the aromatic compound, and the OPLS-DA analysis was performed by orthogonal partial least squares discriminant analysis (OPLS-DA) using the OAV values of the compounds with OAV values >1 as the Y variable. The VIP (Variable Importance in Projection) values of six compounds, ethyl isobutyrate, ethyl hexanoate-D, 2-methylpropanal, ethyl octanoate, ethyl butanoate-D, and Isoamyl acetate-D, were calculated to be higher than one between groups, indicating that these six compounds may influence aroma differences. It is essential to recognize that the results of this study have implications for understanding the quality differences between different varieties of wines and for developing wines that have the characteristics of those varieties.