Optimization of a headspace solid-phase micro-extraction method to quantify volatile compounds in plain sufu, and application of the method in sample discrimination

Elucidation of the Impact of Steaming on the Key Odorants of Jinhua Dry-Cured Ham Using the Sensomics Approach

Jinhua dry-cured ham (JDH) is a traditional fermented meat product favored by Chinese consumers. In this paper, the impact of steaming on the key odorants of JDH was investigated using the sensomics approach. Compounds with odor activity values (OAV) ≥1 were re-engineered in a triglyceride matrix to imitate the odor profiles of both raw and steamed JDHs. The aroma-active compounds were then confirmed by recombination and omission tests using triangle tests. The odor profiles of raw and steamed JDHs were obtained by quantitative descriptive analysis to compare the differences between the original and recombined models. The results showed that pentanal, hexanal, dimethyl trisulfide, (E,E)-2,4-decadienal, (E)-2-heptenal, furaneol, 3-methylbutanoic acid, 1-octen-3-one, and methional influenced the overall raw JDH odor significantly. Furaneol was first reported as a key compound that provides a caramel smell to the raw JDH. Apart from (E)-2-heptenal, dimethyl trisulfide, furaneol, 3-methylbutanoic acid, and methional, the remaining three compounds including 2-furfurylthiol, benzeneacetaldehyde, and phenylethyl alcohol showed a significant influence on the odor profile of steamed JDH. The statistical analysis of the odor profiles showed an 80.0% similarity between the recombination raw JDH and the real raw JDH, and a 76.3% similarity between the model and the real steamed JDH.

Microbiology, flavor formation, and bioactivity of fermented soybean curd (furu): A review

Soybeans are an important plant-based food but its beany flavor and anti-nutritional factors limit its consumption. Fermentation is an effective way to improve its flavor and nutrition. Furu is a popular fermented soybean curd and mainly manufactured in Asia, which has been consumed for thousands of years as an appetizer because of its attractive flavors. This review first classifies furu products on the basis of various factors; then, the microorganisms involved in its fermentation and their various functions are discussed. The mechanisms for the formation of aroma and taste compounds during fermentation are also discussed; and the microbial metabolites and their bioactivities are analyzed. Finally, future prospects and challenges are introduced and further research is proposed. This information is needed to protect the regional characteristics of furu and to regulate its consistent quality. The current information suggests that more in vivo experiments and further clinical trials are needed to confirm its safety and the microbial community needs to be optimized and standardized for each type of furu to improve the production process.

Exploring Core Microbiota Based on Characteristic Flavor Compounds in Different Fermentation Phases of Sufu

Sufu, a Chinese traditional fermented soybean product, has a characteristic foul smell but a pleasant taste. We determined the core functional microbiota and their metabolic mechanisms during sufu fermentation by examining relationships among bacteria, characteristic flavor compounds, and physicochemical factors. Flavor compounds in sufu were detected through headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry, and the microbial community structure was determined through high-throughput 16S rRNA sequencing. The results showed that the fermentation process of sufu could be divided into early and late stages. The early stage was critical for flavor development. Seven microbiota were screened based on their abundance, microbial relevance, and flavor production capacity. Five microbes were screened in the early stage: Pseudomonas, Tetragenococcus, Lysinibacillus, Pantoea, and Burkholderia–Caballeronia–Paraburkholderia. Three microbes were screened in the late stage: Exiguobacterium, Bacillus, and Pseudomonas. Their metabolic profiles were predicted. The results provided a reference for the selection of enriched bacterial genera in the fermentation process and controlling applicable process conditions to improve the flavor of sufu.

Dynamic correlations between major enzymatic activities, physicochemical properties and targeted volatile compounds in naturally fermented plain sufu during production

Dynamic changes and correlations between physicochemical properties, 14 targeted volatile compounds (TVCs) and six groups of enzyme activities during eight production stages of naturally fermented plain sufu were explored. Multiple factor analysis was used to discriminate between and group the samples into three clusters: cluster I comprised tofu and pehtze; cluster II comprised dried pehtze and salted pehtze; cluster III involved the aging stages. Clusters I and II were characterised by higher enzyme activities, while cluster III was characterised by the presence of diverse TVCs. Protease and esterase were strongly correlated with most of the TVCs. Esterase, in particular, contributed to the formation of three high molecular weight esters, namely, ethyl dodecanoate, ethyl (Z)-9-octadecenoate and ethyl (Z, Z)-9,12-octadecadienoate. The enzymes found contributed to the texture and flavour of naturally fermented sufu and will provide a good guide and control for using the enzymes directly to ripen sufu products.

Microwave-Assisted Extraction Coupled with Mass Spectrometry for Determining Five Volatile Compounds from Soy Sauces

As a popular fermented condiment in oriental countries, soy sauce plays a more and more important role in modern food culture due to its unique smell and delicious taste. With the help of microwave extraction and gas chromatography-tandem mass spectrometry, the sample preparation method is aimed to determine the content of cyclohexane, benzene, toluene, chlorobenzene, and styrene in soy sauce. The method was validated by examining the linearity, accuracy, specificity, precision, the limit of detection, and quantitation. Meanwhile, three key factors have an impact on the efficiency and accuracy of the method including extracting solvent, temperature, and time which were optimized. The result shows that the recoveries of spiked analytes ranged from 80.86% to 105.71%, the relative standard deviation of intraday and interday precision was no more than 12.1% and 12.5%, and the limit of detection and quantitation were 0.25-1.00 ng/mL and 0.50-2.00 ng/mL, respectively. The results also indicated that the proposed method was a simple, reliable, and sensitive approach for the determination trace amount of five harmful volatile organic compounds from soy sauce.

Degradation of the mixture of ethyl formate, propionic aldehyde, and acetone by Aeromonas salmonicida: A novel microorganism screened from biomass generated in the citric acid fermentation industry

Microorganisms play important roles in the degradation of volatile organic compounds. Aeromonas salmonicida strain (AEP-3) generated from biomass in the citric acid fermentation industry was screened and subjected to denaturing gradient gel electrophoresis (DGGE) fingerprinting and 16S rDNA gene sequencing. The growth conditions of AEP-3 in Luria-Bertani broth were optimized at 25 °C and approximately pH 7. AEP-3 was used to degrade ethyl formate, propionic aldehyde, or acetone alone and their mixture. The concentrations of ethyl formate, propionic aldehyde, and acetone were below 7500, 600, and 800 mg L^-1, respectively, and their maximum degradation efficiencies were 100%, 92.41%, and 34.75%. AEP-3 first degraded acetone and propionic aldehyde in the mixture, followed by ethyl formate. The degradation pathways of these organic compounds in the mixture and their substrate interactions during degradation were explored. Propionic aldehyde was first converted into propionic acid in the metabolic process and was involved in the subsequent carboxylic acid cycle. By contrast, ethyl formate was first hydrolyzed into formic acid and ethanol. Then, formic acid participated in the cyclic metabolism of carboxylic acid, whereas, ethanol was hydrolyzed into acetaldehyde and acetic acid through alcohol and aldehyde dehydrogenase. Additionally, acetone directly interacted with nitrate in the medium under the action of hydrogen ions and produced carbon dioxide, water, and nitrogen. Overall, this study provides a new degrading bacterium biodegradability toward the exhaust gas of citric acid fermentation.

Optimization of solid phase microextraction combined with gas chromatography-mass spectrometry (GC-MS) to analyze aromatic compounds in fresh tomatoes

In this study, conditions for solid-phase microextraction coupled to gas chromatography-mass spectrometry to extract and analyze volatile compounds from fresh tomatoes (Solanum lycopersicum cv. Fendi) were optimized. Four main experimental parameters were optimized, including internal standard, fiber material coating, extraction temperature, and salt concentration. The optimal extraction conditions were 85 μm Carboxen/Polydimethylsiloxane fiber, 60°C extraction temperature, 1-heptanol as an internal standard, and without adding sodium chloride in the tomato sample. Analysis of tomato fruit samples using these optimized conditions allowed us to identify 37 volatile compounds that could be grouped into seven categories: aldehydes (11), hydrocarbons (7), alcohols (7), ketones (5), oxygen-containing heterocyclic compounds (3), esters (3), sulfur-and nitrogen-containing heterocyclic compounds (1). PRACTICAL APPLICATIONS: In this study, we optimized a method to extract tomato flavor compounds. In recent years, many consumers complained that tomatoes have poor flavor. A method to extract flavor compounds will assist in characterizing the compounds that contribute to tomato flavor and could be used in the development of tomatoes that have enhanced flavor.