Effects of different cooking methods on free fatty acid profile, water-soluble compounds and flavor compounds in Chinese Piao chicken meat

Effect of Stewing Time on the Small Molecular Metabolites, Free Fatty Acids, and Volatile Flavor Compounds in Chicken Broth

Chicken broth has a taste of umami, and the stewing time has an important effect on the quality of chicken broth, but there are fewer studies on the control of the stewing time. Based on this, the study was conducted to analyze the effects of different stewing times on the sensory, small molecular metabolites, free fatty acids, and volatile flavor compounds contents in chicken broths by liquid chromatography-quadrupole/time-of-flight mass spectrometry, gas chromatography-mass spectrometry, headspace solid-phase microextraction, and gas chromatography-mass spectrometry. Eighty-nine small molecular metabolites, 15 free fatty acids, and 86 volatile flavor compounds were detected. Palmitic and stearic acids were the more abundant fatty acids, and aldehydes were the main volatile flavor compounds. The study found that chicken broth had the best sensory evaluation, the highest content of taste components, and the richest content of volatile flavor components when the stewing time was 2.5 h. This study investigated the effect of stewing time on the quality of chicken broth to provide scientific and theoretical guidance for developing and utilizing local chicken.

Characterization of key aroma compounds in roasted chicken using SPME, SAFE, GC-O, GC-MS, AEDA, OAV, recombination-omission tests, and sensory evaluation

Aroma compounds in the roasted breasts, thighs and skins of chicken were isolated by solvent-assisted flavor evaporation (SAFE), quantitated by gas chromatography-olfactometry-mass (GC-O-MS), analyzed by aroma extract dilution analysis (AEDA), and determined by recombination-omission tests and sensory evaluation. Forty-seven aroma compounds in total, including aldehydes, ketones, furans, pyrazines, and furanones, were selected by AEDA. Twenty-five compounds were selected as pivotal odorants (Odor Activity Value, OAV ≥ 1). Twenty aroma compounds significantly were identified by recombination and omission experiments. Anethole (fennel odor) was the highest OAV (＞ 1843). Hexanal (grassy) and (E, E)-2,4-decadienal (meaty) were the most abundant aldehydes identified in roasted chicken. 1-octen-3-ol (mushroom), methanethiol (cabbage) and dimethyl trisulfide (areca, sulfur) were considered the key compounds of the breast and thighs of roasted chicken. Notably, furanone and pyrazines, 4-hydroxy-5-methyl-3(2H)-furanone (caramel, sweet and burning odor), 3-ethyl-2,5-dimethylpyrazine (nutty, toasty) and 2,3-dimethyl-5-ethylpyrazine (nutty, toasty) had the most significant effect on roasted chicken odor, especially in the skin.

Unraveling the Formation Mechanism of Egg's Unique Flavor via Flavoromics and Lipidomics

Egg products after thermal treatment possess a unique flavor and are favored by consumers. In this study, the key aroma-active compounds of egg yolk products and their formation mechanism during thermal treatment were investigated. The volatile aroma compounds in egg yolks were monitored using an electronic nose, gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry-mass spectrometry (GC-O-MS), and the lipid molecular species were explored using ultra-high-performance liquid chromatography- mass spectrometry with a Q-Exactive HF-X Orbitrap (UPLC-Q-Exactive HF-X). A total of 68 volatile compounds were identified. Boiled eggs mainly derived their flavor from hexanal, 2-pentyl-furan, 2-butanone, 3-methyl-butanal and heptane. Meanwhile, fried eggs relied mainly on 14 compounds, the most important of which were 2-ethyl-3-methyl-pyrazine, 3-ethyl-2,5-dimethyl-pyrazine, 2-ethyl-3,5-dimethyl-pyrazine, nonanal and 2,3-diethyl-5-methyl-pyrazine, providing a baked and burnt sugar flavor. A total of 201 lipid molecules, belonging to 21 lipid subclasses, were identified in egg yolks, and 13 oxidized lipids were characterized using a molecular network. Phosphoethanolamines (PEs) containing polyunsaturated fatty acids were the primary flavor precursors contributing to the development of egg yolks' flavor, participating in lipid oxidation reactions and the Maillard reaction and regulating the production of aldehydes and pyrazine compounds. This study provides reference and guidance for the development of egg yolk flavor products.

Changes in Meat of Hu Sheep during Postmortem Aging Based on ACQUITY UPLC I-Class Plus/VION IMS QTof

Meat and meat products have a critical role in the human diet as important high-nutrient foods that are widely consumed worldwide. This study evaluated the effects of postmortem aging on Hu sheep's meat quality in the longissimus dorsi (LD) muscle during postmortem aging. The samples were stored at 4 ± 1 °C; the meat quality was measured at 6 h, 12 h, 24 h, 36 h, 48 h, 72 h, 96 h, 120 h, 144 h, and 168 h of postmortem aging. The results showed that, during the postmortem aging process, the pH of the muscles first decreased and then increased, and the shear force first increased and then decreased. The muscle fiber skeleton began to degrade, and the overall meat quality was improved to some extent. In addition, through ACQUITY UPLC I-Class Plus IMS Qtof identification of the muscle samples at different time points during the postmortem maturation process of the meat of Hu sheep, a total of 2168 metabolites were identified, and 470 metabolites were screened based on the VIP, P, and FC values, of which 79 were involved in KEGG pathways. In addition, pathways such as sphingolipid metabolism, glycerophospholipid metabolism, phenylalanine metabolism, and fatty acid elongation and degradation play an important role in the metabolic product changes in the meat of Hu sheep throughout the entire maturation process. These findings provide some insights into the changes in meat quality during the post-slaughter maturation process of lake lamb.

Identification of characteristic aroma compounds in chicken meat and their metabolic mechanisms using gas chromatography-olfactometry, odor activity values, and metabolomics

Aroma has an important influence on the aroma quality of chicken meat. This study aimed to identify the characteristic aroma substances in chicken meat and elucidate their metabolic mechanisms. Using gas chromatography-olfactometry and odor activity values, we identified nonanal, octanal, and dimethyl tetrasulfide as the basic characteristic aroma compounds in chicken meat, present in several breeds. Hexanal, 1-octen-3-ol, (E)-2-nonenal, heptanal, and (E,E)-2,4-decadienal were breed-specific aroma compounds found in native Chinese chickens but not in the meat of white-feathered broilers. Metabolomics analysis showed that L-glutamine was an important metabolic marker of nonanal, hexanal, heptanal, octanal, and 1-octen-3-ol. Exogenous supplementation experiments found that L-glutamine increased the content of D-glucosamine-6-P and induced the degradation of L-proline, L-arginine, and L-lysine to enhance the Maillard reaction and promote the formation of nonanal, hexanal, heptanal, octanal, and 1-octen-3-ol, thus improving the aroma profile of chicken meat.

Changes provoked by altitudes and cooking methods in physicochemical properties, volatile profile, and sensory characteristics of yak meat

The present study aimed to shed light on the effects of altitudes and three cooking methods (boiling, steaming, and roasting) on the physicochemical quality, volatile profile, and sensorial characteristics of yak meat. Composite meat samples were prepared to represent each cooking method and altitude level from the longissimus thoracis et lumborum (LTL) muscle of nine yaks. The techniques employed were gas chromatography-mass spectrometry (GC-MS) and electronic nose (E-nose) along with chemometrics analysis to study the changes occurring in yak volatile profile, and TBARS measurement in lipid oxidation during cooking. Among the cooking methods, boiling and steaming exhibited higher protein and fat content while lower volatile compound contents. Additionally, roasted yak meat received the highest sensory scores, along with decreased L*-values, while elevated a*- and b*-values, and tenderness. A total of 138 volatile compounds were detected, and among them, 36 odorants were identified as odor-active compounds in cooked yak meat. It is evidenced that low-altitude yak presented more complex and richer flavor profiles than high-altitude ones. Moreover, yak meat from low- and high-altitude was classified into two groups by an electronic nose (E-nose) owing to distinct flavor characteristics. Overall, roasted yak meat originating from low altitudes tends to be more popular from a sensory perspective.

Correlation Analysis between Volatile Compounds and Quality Attributes in Pork Tenderloin in Response to Different Stir-Frying Processes

Volatile compounds and physicochemical properties of meat are significantly changed by cooking processes. This study explored the influence of different stir-frying temperatures and times on the dynamic changes of the physicochemical characteristics and volatiles of pork tenderloin and determined the correlation between them. Results showed that time played more of a role than temperature. At the same temperature, the water content decreased (p < 0.05) and the cooking loss increased (p < 0.05) with stir-frying time extending. The L* value and the b* value showed first an increasing and then decreasing trend (p < 0.05), while the a* value significantly increased (p < 0.05). The higher the cooking temperature of sample, the faster the indexes changed. In stir-fried samples, 50 volatiles were identified. Correlation analysis showed that among the quality attributes, b* value and water content had the strongest impact on volatiles. The water content was negatively correlated with most of the compounds attributed to the desired aroma of stir-fried samples, while the correlation between the b* value and these volatiles was positive. Hence, changes in the types and contents of volatiles in stir-fried pork tenderloin could be predicted by detection of b* value and water content.

Effects of Age on Compounds, Metabolites and Meat Quality in Beijing-You Chicken Breast Meat

The physical properties, free amino acids, and metabolites of Beijing-You chicken (BYC) breast meat aged 90, 120, and 150 days were analyzed to investigate the flavor changes with age. The shear force and intramuscular fat increased from 90 to 120 days significantly. The contents of total free amino acids and essential amino acids decreased from 90 to 120 days significantly. No significant differences were detected between 120 and 150 days. The contents of sweet amino acids, bitter amino acids, and umami amino acids showed no significant differences between different ages. In addition, GC-MS and LC-MS were integrated for metabolite detection in breast meat. A total of 128, 142, and 88 differential metabolites were identified in the comparison groups of 120 d vs. 90 d, 150 d vs. 90 d, and 150 d vs. 120 d. Amino acids and lipids were the main differential metabolites. The pathway analysis showed that arginine biosynthesis, histidine metabolism, purine metabolism, and cysteine and methionine metabolism were the main pathways involved in flavor formation during BYC development. It was also found that the metabolites associated with flavor, such as methionine, cysteine, glucose, anserine, arachidonic acid, and glycerol 1-phosphate, were significantly affected by age.

Comparison of the Fatty Acid Composition and Small Molecular Metabolites between Yanjin Blackbone Chicken and Piao Chicken Meat

The fatty acid composition and small molecular metabolites in breast and leg meat of Yanjin blackbone chickens (YBC) and Piao chickens (PC) were detected by gas chromatography-mass spectrometry and liquid chromatography-quadrupole static field orbital trap mass spectrometry. Thirty-two fatty acids were detected, and the total fatty acid content of PC was significantly higher than that of YBC (p<0.05). Oleic acid, linoleic acid, palmitic acid, stearic acid, and arachidonic acid were the main fatty acids in the two chicken varieties, and the composition of fatty acids in the two varieties were mainly unsaturated fatty acids, being more than 61.10% of the total fatty acids. Meanwhile, 12 and 16 compounds were screened out from chicken legs and chicken breasts of YBC and PC, respectively, which had important contributions to the differences between groups.

Understanding the role of lipids in aroma formation of circulating non-fried roasted chicken using UHPLC-HRMS-based lipidomics and heat transfer analysis

The role of lipids in aroma formation of circulating non-fried roasted (CNR) chicken with different roasting times was studied using ultra-high performance liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS)-based lipidomics and heat transfer analysis. Thirteen odorants were confirmed as important aroma compounds of CNR chicken, including dimethyl trisulfide, 3,5-dimethyl-2-ethylpyrazine, nonanal, and 1-octen-3-ol. A comprehensive lipidomics analysis identified 1254 lipids in roasted chickens, classified into 23 distinct lipid categories that included 281 phosphatidylcholines (PC), 223 phosphatidylethanolamines (PE), and 202 triglycerides (TG). Using OPLS-DA analysis, the lipid PG (18:1_18:1) showed promise as a potential biomarker for distinguishing between chickens subjected to CNR treatments with varying roasting times. The lipids PC, PE, and their derivatives are likely to play a crucial role in the formation of aroma compounds. In addition, TGs that contributed to the retention of key odorants in roasted chicken included TG (16:0_16:0_18:1), TG (16:0_16:0_18:0), and TG (16:0_18:1_18:1). Findings further showed that lower water activity and specific heat capacity promoted the formation and retention of aroma compounds during the CNR process. This study contributed to a better understanding of the formation of aroma compounds through lipid oxidation in roasted chicken.

Mechanisms of cooking methods on flavor formation of Tibetan pork

To obtain flavor-enriched Tibetan pork products, the impact of oxidation degree on the flavor of Tibetan pork with different cooking methods (microwaving, frying, boiling, and air frying) was evaluated using an E-nose, an E-tongue, GC-MS, and LC-MS. The level of oxidation was lower in M and F and higher in B and AF groups. Hexanal, pentanal, benzaldehyde, 1-octen-3-ol, and 3-hydroxy-2-butanone were identified as significant contributors to cooked samples. The volatile abundance of microwaved, fried, boiled, and air-fried pork was 1.61, 1.22, 1.47, and 1.69 times higher than raw, respectively. Leucine and threonine were detected to be the highest in the AF group, which were 1.30 and 3.60 times greater than RAW, respectively. In summary, oxidation of lipids and proteins caused by cooking treatments was the main source of flavor in cooked Tibetan pork. Air-frying treatment could greatly promote the production of flavor compounds and give unique flavor to Tibetan pork.

Multivariate Statistical Techniques: A New Approach to Identify the Commercial Properties of Mixtures of Flours of Lentinula edodes and Cocoa Pod Husk

Lentinula edodes is known to show high nutritional and organoleptic properties and can be mixed with different by-products in the production of new foods with important functional characteristics. Cocoa pod husk (CPH) is the main by-product in the cocoa industry and presents important bioactivities. In this research, two mixtures were applied based on Lentinula edodes mushroom flour from fifty different strains (strain 1 to strain 50) and cocoa pod husk flour (CPHF): 60% Lentinula edodes mushroom flour from each strain mixed with 40% CPHF (Mixture 1), and 80% Lentinula edodes mushroom flour from each strain mixed with 20% CPHF (Mixture 2). The parameters evaluated were moisture, proteins, fat, total dietary fiber (TDF), ash, carbohydrates, antioxidant capacity, antimicrobial activity, pH and water activity (aw). The multivariate statistical techniques evaluated those samples that exhibited the highest degree of correlation with the distinct chemical and commercial parameters, showing that sample 13 of both mixture flours (M1 and M2) obtained by the mushrooms of L. edodes (strain 13) with CPH indicated the higher significant of the parameters. In addition, the sensory test of the best flour (sample 13) was applied to 50 panelists, presenting the best sensory characteristics, such as color, aroma, texture and general acceptability.

Dynamic changes in the water distribution and key aroma compounds of roasted chicken during roasting

The effects of roasting times (0, 2, 4, 6, 8, 10, 12, and 14 min) on the dynamic changes of the water distribution and key aroma compounds in roasted chicken during the electric roasting process were studied. In total, 36 volatile compounds were further determined by GC-MS and 11 compounds, including 1-octen-3-ol, 1-heptanol, hexanal, decanal, (E)-2-octenal, acetic acid hexyl ester, nonanal, 2-pentylfuran, heptanal, (E, E)-2,4-decadienal and octanal, were confirmed as key aroma compounds. The relaxation time of T22 and T23 was increased first and then decreased, while the M22 and M23 in roasted chicken were decreased and increased with increasing roasting time, respectively. The fluidity of the water in the chicken during the roasting process was decreased, and the water with a high degree of freedom migrated to the water with a low degree of freedom. In addition, the L*, a*, b*, M23 and all amino acids were positively correlated with all the key aroma compounds, while T22, M22 and moisture content were negatively correlated with all the key aroma compounds.

Effects of blackberry polysaccharide on the quality improvement of boiled chicken breast

Blackberry polysaccharide was isolated from blackberry powder with 70% ethanol. The crude polysaccharide was composed of 95.44% glucose, 2.01% arabinose, 1.81% galactose and 0.74% glucuronic acid. Chicken breast meat was only marinated with different concentrations of the isolated blackberry polysaccharide (1 g/kg, 3 g/kg) for 24 h at a ratio of material to liquid of 1:3, and boiled at 80℃ for 1 h. The differences in texture, water distribution and volatile flavor components among different groups （adding 0,1,3 g/kg blackberry polysaccharide) were investigated. The results showed that the addition of blackberry polysaccharide could significantly improve the hardness of chicken breast, the transformation of free water to bound water, the overall flavor characteristics of the control group and the addition of different concentrations of blackberry polysaccharide were significantly different, and the concentration of volatile flavor substances in boiled chicken breast was reduced.

Effect of Cooking Method and Doneness Degree on Volatile Compounds and Taste Substance of Pingliang Red Beef

This study used gas chromatography-ion mobility spectrometry (GC-IMS) and high-performance liquid chromatography (HPLC) methods to examine the impact of cooking methods and doneness on volatile aroma compounds and non-volatile substances (fatty acids, nucleotides, and amino acids) in Pingliang red beef. The flavor substances' topographic fingerprints were established, and 45 compounds were traced to 71 distinct signal peaks. Pingliang red beef's fruity flavor was enhanced thanks to the increased concentration of hexanal, styrene, and 2-butanone that resulted from instant boiling. The levels of 3-methylbutanal, which contributes to the characteristic caramel-chocolate-cheese aroma, peaked at 90 min of boiling and 40 min of roasting. The FFA content was reduced by 28.34% and 27.42%, respectively, after the beef was roasted for 40 min and instantly boiled for 10 s (p > 0.05). The most distinctive feature after 30 min of boiling was the umami, as the highest levels of glutamate (Glu) (p < 0.05) and the highest equivalent umami concentration (EUC) values were obtained through this cooking method. Additionally, adenosine-5'-monophosphate (AMP) and inosine-5'-monophosphate (IMP) decreased with increasing doneness compared to higher doneness, indicating that lower doneness was favorable in enhancing the umami of the beef. In summary, different cooking methods and doneness levels can affect the flavor and taste of Pingliang red beef, but it is not suitable for high-doneness cooking.

Effect of Different Heat Treatments on the Quality and Flavor Compounds of Black Tibetan Sheep Meat by HS-GC-IMS Coupled with Multivariate Analysis

There are limited reports about the effect of different heat treatments on the quality and flavor of Black Tibetan sheep meat. The current study examined the effect of pan-frying, deep-frying, baking, and boiling treatment on the quality of Black Tibetan sheep meat; the amino acid, fatty acid, and volatile flavor compounds (VFCs) were investigated by a texture analyzer, ultra-high-performance liquid chromatography (UHPLC), gas chromatography (GC), and headspace-gas chromatography-ion mobility (HS-GC-IMS). The key VFCs were identified through orthogonal partial least squares discrimination analysis (OPLS-DA), and variable importance projection (VIP) values. In addition, Pearson’s correlations between meat quality parameters and key VFCs were examined. The sensory scores, including texture, color, and appearance, of baked and pan-fried meat were higher than those of deep-fried and boiled meat. The protein (40.47%) and amino acid (62.93 µmol/g) contents were the highest in pan-fried meat (p < 0.05). Additionally, it contained the highest amounts of monounsaturated and polyunsaturated fatty acids, such as oleic, linoleic, and α-linolenic acids (p < 0.05). Meanwhile, pan-fried and deep-fried meat had higher amounts of VFCs than baked meat. The OPLS-DA similarity and fingerprinting analyses revealed significant differences between the three heat treatment methods. Aldehydes were the key aroma compounds in pan-fried meat. Importantly, 3-methylbutyraldehyde and 2-heptanone contents were positively correlated with eicosenoic, oleic, isooleic, linoleic, α-Linolenic, and eicosadiene acids (p < 0.05). To sum up, pan-fried Black Tibetan sheep meat had the best edible, nutritional, and flavor quality.

Effect of cooking modes on quality and flavor characteristic in Clitocybe squamulose chicken soup

The effects of cooking modes [cooking in stainless-steel pot (SS), ceramic pot (CP), and electrical ceramic stewpot (EC) with different stewing time] on chemical compositions, whiteness, 5'-nucleotides, fatty acids (FAs), sensory quality and flavor substances in chicken soup added Clitocybe squamulose (Pers.) Kumm (a natural edible fungus) were investigated. The results showed that CP chicken soup had higher soluble solid matter (5.83 g/100 mL), total sugar (2.38 mg/mL), crude protein (7.58 g/100 g), and 5'-nucleotides (325.53 mg/mL) than EC and SS chicken soups. 48 volatile flavor compounds, mainly aldehydes and alkanes, were found by gas chromatography-mass spectrometry (GC-MS), and the characteristic flavor substances were identified by Principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA). Hexanal, (E,E)-2,4-decadienal and 3-methyl-hexadecane were the most abundant differential volatile compounds in the CP chicken soup. Additionally, the results of sensory evaluation showed that the chicken soup cooked in CP had the higher values of aroma, taste, and overall acceptability. Our results indicate that CP mode might be the best option for cooking chicken soup. This study provides a new perspective in the improvement of the quality and flavor of chicken soup by using an appropriate cooking mode. Theoretical support for the use of various cooking modes is also discussed to improve the quality of chicken soup at home and in the industry.

Effects of four cooking methods on flavor and sensory characteristics of scallop muscle

This work aimed to explore the influence of four different cooking methods (Boiling, roasting, frying, and microwaving) on the sensory characteristics of scallop muscles. Headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and electronic nose (e-nose) were combined to analyze the aroma of scallops. Combined with the results of free amino acids and electronic tongue (e-tongue), the taste changes of different samples were analyzed. Furthermore, texture profile and microstructure analysis jointly showed the influence of cooking methods on texture. The results showed that frying was the most suitable cooking method for scallop muscle because it resulted the best tasted products, boiled scallops retain the highest similarity to fresh scallops. Besides, a higher level of lipid oxidation and Maillard reaction resulted in significant increase in aldehydes, ketones, furans, umami, and sweet amino acid. For the boiled sample, the loss of water-soluble compounds and less fat oxidation resulted in fewer flavor substances and free amino acids, along with looser organizational structure and poorer sensory quality. The research showed that besides the texture of scallop muscle, volatile organic compounds and free amino acids as well as their mutual roles in taste and smell were also important to sensory receptivity.

Effect of Different Cooking Methods on Nutrients, Antioxidant Activities and Flavors of Three Varieties of Lentinus edodes

This work evaluated the effect of different cooking methods (boiling, steaming, microwaving, frying and pressure cooking) on the nutrients, antioxidant activities, volatile and nonvolatile taste-active components of three varieties of Lentinus edodes (808, 0912 and LM) from Guizhou Province. The results showed that LM had the most polysaccharides, 0912 had the most minerals, but LM, 808 and 0912 had low amounts of polyphenols, dietary fiber and proteins, respectively. The dietary fiber and protein were decreased by 4.1~38.7% and 4.1~44.0% during cooking, while microwaving improved the nutritional value of the Lentinus edodes by increasing the polysaccharide (88~103 mg/g to 93~105 mg/g) and polyphenol content (6.4~8.1 mg/g to 7.5~11.2 mg/g), thereby strengthening the antioxidant activity. The nucleotides were all destroyed after cooking, especially frying or boiling. The glutamate content was the highest in LM and 808, and the methionine content appeared to be the highest in 0912. Pressure cooking and frying increased the proportions of sweet and umami amino acids and decreased the proportion of bitter amino acids, creating more aroma-active compounds. In summary, microwaving increased the content of bioactive compounds and antioxidant activities, and it preserved nonvolatile taste-active components, while pressure cooking and frying were the best methods for increasing the flavor compounds.

Molecular signatures of organic particulates as tracers of emission sources

Chemical signature of airborne particulates and deposition dusts is subject of study since decades. Usually, three complementary composition markers are investigated, namely, (i) specific organic compounds; (ii) concentration ratios between congeners, and (iii) percent distributions of homologs. Due to its intrinsic limits (e.g., variability depending on decomposition and gas/particle equilibrium), the identification of pollution sources based on molecular signatures results overall restricted to qualitative purposes. Nevertheless, chemical fingerprints allow drawing preliminary information, suitable for successfully approaching multivariate analysis and valuing the relative importance of sources. Here, the state-of-the-art is presented about the molecular fingerprints of non-polar aliphatic, polyaromatic (PAHs, nitro-PAHs), and polar (fatty acids, organic halides, polysaccharides) compounds in emissions. Special concern was addressed to alkenes and alkanes with carbon numbers ranging from 12 to 23 and ≥ 24, which displayed distinct relative abundances in petrol-derived spills and exhausts, emissions from microorganisms, high vegetation, and sediments. Long-chain alkanes associated with tobacco smoke were characterized by a peculiar iso/anteiso/normal homolog fingerprint and by n-hentriacontane percentages higher than elsewhere. Several concentration ratios of PAHs were identified as diagnostic of the type of emission, and the sources of uncertainty were elucidated. Despite extensive investigations conducted so far, the origin of uncommon molecular fingerprints, e.g., alkane/alkene relationships in deposition dusts and airborne particles, remains quite unclear. Polar organics resulted scarcely investigated for pollution apportioning purposes, though they looked as indicative of the nature of sources. Finally, the role of humans and living organisms as actual emitters of chemicals seems to need concern in the future.

Effect of CO2 on the spoilage potential of Shewanella putrefaciens target to flavour compounds

To investigate the regulation mechanism of CO₂ (0% CO₂, 20% CO₂, 60% CO₂, and 100% CO₂) on the spoilage potential of S. putrefaciens target to flavour compounds, the metabolic activity of S. putrefaciens and the changes in flavour compounds extracted from inoculated large yellow croakers were evaluated. Results showed that CO₂ significantly reduced biofilm formation capacity and suppressed synthesis of intracellular adenosine triphosphate (ATP). The production of unpleasant flavour compounds, such as total volatile basic nitrogen (TVB-N), trimethylamine (TMA), inosine (HxR), hypoxanthine (Hx), histidine, lysine, histamine, putrescine, 1-octen-3-ol, hexanal and benzaldehyde, was inhibited by CO₂. The hydrolysis and oxidation of lipid in CO₂-treated samples were alleviated and unsaturated fatty acids (UFAs) were in a higher percentage. In summary, CO₂ efficiently reduced the spoilage potential of S. putrefaciens and contributed to better flavour quality of samples during 4 °C storage. A more effective inhibition by 100% CO₂ was observed.

Multiple Technologies Combined to Analyze the Changes of Odor and Taste in Daokou Braised Chicken during Processing

This study analyzed the changes of odor and taste in Daokou braised chicken during processing by GC-MS, GC-IMS, e-nose and e-tongue. The 75 and 55 volatile compounds identified in Daokou braised chicken by GC-MS and GC-IMS, respectively, included hydrocarbons, aldehydes, alcohols, terpenes, ketones, heterocyclics, esters, acids and phenols; among them, aldehydes, alcohols and ketones were the most abundant. The number and proportion of volatile compounds in Daokou braised chicken changed significantly (p < 0.05) in the process. The proportion of volatile compounds with animal fatty odor, such as aldehydes and alcohols, decreased, while that of esters, ketones and terpenes from spices with fruity fragrance increased, especially in the braising stage. An e-nose showed that the odor intensities of sulfur-containing and nitrogen oxide compounds were higher (p < 0.05) after the braising stage, but weakened after 2 h braising. An e-tongue showed that saltiness and richness increased significantly (p < 0.05) after braising. The results of these four techniques showed that braising promoted the release of flavor compounds, and was beneficial to salt penetration and umami release. However, long braising could lead to weakened flavor intensity and the introduction of bitterness and astringency. This study also found that GC-IMS and e-nose were more sensitive to trace compounds such as sulfur-containing and nitrogen oxide compounds, esters, acids and phenolics in Daokou braised chicken than GC-MS. The use of multiple technologies could provide more comprehensive flavor profiles for Daokou braised chicken during processing. This study provides insights into the control of flavor of Daokou braised chicken, and may be of practical relevance for the poultry industry.