Flavor improvement of fermented soy sauce by extrusion as soybean meal pretreatment

Partial substitution of wheat flour with soybean and gluten powder: impact on flavor characteristics of Pixian Douban-Meju and its quality

BACKGROUND

In this study, different proportions of soybean flour and gluten flour were used as partial replacements for wheat flour for the fermentation of Pixian Douban-Meju (PXDB). The aim was to study the effects of soybean flour/gluten flour on the quality improvement of PXDB.

RESULTS

In comparison with the control group (CT) (0% substitution of wheat flour), substitution of wheat flower with 12.5% soybean flour (the H2 group), 7.5% gluten flour (G2), and 10% gluten flour (G3) improved the amino acid nitrogen content by 3.8%, 5.6%, and 9.4% respectively. The mixtures of wheat flour and gluten flour (G2 or G3) increased the organic acid and free amino acid content. The results of two-dimensional gas chromatography mass spectrometry (GC × GC-MS) showed that the amount of key aroma substances increased about sixfold in comparison with the CT group (194.61 g.kg-1 ), achieving 1283.67, 1113.883, and 1160.19 g.kg-1 in the H2, G2, and G3 groups, respectively. There were also more aldehydes and pyrazines in all the substitution groups. Quantitative descriptive analysis indicated that the G3 sample presented the best organoleptic quality with a reddish-brown color and a more mellow aroma than the control sample.

CONCLUSION

In conclusion, the fermentation of G3 resulted in higher quality PXDB-meju, showing that partial substitution of wheat flour with gluten improved the quality of PXDB. © 2023 Society of Chemical Industry.

Pyrazines in food samples: Recent update on occurrence, formation, sampling, pretreatment and analysis methods

Pyrazines are a class of active aromatic substances existing in various foods. The accumulation of pyrazines has an impact on flavor and quality of food products. This review encompasses the formation mechanisms and control strategies of pyrazines via Maillard reaction (MR), including the new reactants and emerging techniques. Pyrazines characteristics are better understood through the developed sample pretreatments and detection methods. Herein, an in-depth review of pretreatments and analysis methods since 2010 is presented to explore the simple, fast, green, and effective strategies. Sample preparation methods include liquid phase extraction, solid phase extraction, supercritical fluid extraction, and microextraction methods such as liquid phase microextraction, and solid phase microextraction, etc. Detections are made by chromatographic methods, and sensors, etc. Advantages and limitations are discussed and compared for providing insights to further studies.

Comparison of Flavor Profile Relationship of Soy Sauce under Different Storage Conditions

To elucidate the relation of flavor in soy sauce (SS) kept at room temperature (SSAT) and SS kept under accelerated aging condition (SSAA), four analytical instruments, including electronic nose (E-nose), electronic tongue (E-tongue), gas chromatography-mass spectrometry-olfactory combined with solvent assisted flavor evaporation, and amino acid analyzer, were applied for analyzing the overall flavor profiles and flavor constituents in SSAT and SSAA. The results of E-nose and E-tongue showed overall flavor profile in SSAT for 3 weeks was similar to that of SSAA for 1 week, and 6 weeks (SSAT) was similar to 2 weeks (SSAA). In SS, a total of 35 odor-active compounds were identified and quantitated, and 22 compounds with odor activity value ≥1 were determined as key odorants. The compounds with the highest concentration were 4-hydroxy-2,5-dimethyl-3(2H)-furanone (28,756 μg/mL), followed by acetic acid (8838 μg/mL) and maltol (7984 μg/mL). The heatmap and hierarchical cluster analysis indicated that the concentrations of key odorants and amino acids in SSAT for 3 weeks was close to those of SSAA for 1 week, and 6 weeks (SSAT) was similar to 2 weeks (SSAA). Based on the results obtained above, it was concluded that the flavor changes in SSAA for 1 week were equivalent to those in SSAT for 3 weeks.

Assessment the flavor of soybean meal hydrolyzed with Alcalase enzyme under different hydrolysis conditions by E-nose, E-tongue and HS-SPME-GC-MS

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Enzymatic hydrolysis with Alcalase reduced soybean odor substance 1-octene-3-ol.

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Excessive enzymatic hydrolysis resulted in the deterioration of the hydrolysate flavor.

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The flavour of soybean meal hydrolysates with different hydrolysis conditions could be distinguished by E-tongue.

In the present study, E-nose, E-tongue, and headspace-solid phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC–MS) technology combined with Principal Component Analysis (PCA) were employed to evaluate the flavor characteristics of the volatile and the non-volatile substances generated during the enzymatic hydrolysis of the soybean meal by Alcalase. The results showed that the enzymatic hydrolysis effectively reduced the content of soybean odorous substance 1-octene-3-ol and led to better flavor. However, the excessive enzymatic hydrolysis resulted in the deterioration of the enzymatic hydrolysates flavor. In addition, both radar graph and PCA of E-tongue were able to provide the distribution of flavor substances during the enzymatic hydrolysis of the soybean meal. These results provided a theoretical basis for the improvement of the flavors of the soybean meal and its derived products.

Traditional fermented soybean products: processing, flavor formation, nutritional and biological activities

Traditional fermented soybean food has emerged as an important part of people's dietary structure because of the unique flavors and improved health benefit. During fermentation, the nutrients in soybean undergo a series of biochemical reactions catalyzed naturally by microorganism secreted enzymes. Thereafter, many functional and bioactive substances such as bioactive peptides, unsaturated fatty acids, free soy isoflavones, vitamins and minerals are produced, making fermented soy products more advantageous in nutrition and health. This review comprehensively discusses the historical evolution, distribution, traditional fermentation processing, main sources and characteristics of fermented strains, flavor components, nutritional properties, and biological activities of four traditional fermented soybean foods including douchi, sufu, dajiang, and soy sauce. In the end, we introduce four major challenges encountered by traditional fermented soybean foods including high salt content, formation of biogenic amine, the presence of pathogenic microorganisms and mycotoxins, and quality inconsistency. We conclude that the establishment of scientific quality standard and innovated fermentation processing is the potential solutions to combat the issues and improve the safety of traditional fermented soybean products.

The volatile flavor compounds of Shanghai smoked fish as a special delicacy

In this work, the effects of substrates on volatile flavor compounds of Shanghai smoked fish (SSF) from grass carp was investigated by head space-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) by changing the ratios of soy sauce (15%-25%) to white sugar (10%-20%) and replacing white sugar with reducing sugar (glucose, fructose, and ribose). The results showed the key volatile flavor compounds (ROAV ≥ 1) of SSF were 2,4-decadienal, p-xylene, nonanal, and 1-octen-3-ol with the relative contents of 10.33, 1.14, 4.84, and 1.76%, respectively. Furthermore, the existence of soy sauce had an enhancing role in the production of pyrazines, but no significant difference in white sugar. The contents of isovaleraldehyde and benzeneacetaldehyde were increased when white sugar was replaced with glucose, octanol, and 2-pentyl furan for fructose, no obvious difference in ribose. Moreover, the optimal ratios of soaking solutions were 20% soy sauce and 15% white sugar based on the scoring method of sensory evaluation. This study will provide a theoretical basis for the formation of volatile flavor compounds of SSF. PRACTICAL APPLICATIONS: Grass carp usually grows in freshwater such as pond or lake, but bacteria with earthy smell are easily attached to plankton such as diatom and cyanobacteria leading to the accumulation of bad odor substances through the food chain. Shanghai smoked fish (SSF) deeply loved by public is a traditional special dish with crispy crust and delicious taste. The attractive flavor of grass carp could be increased with the help of the Maillard reaction (MR) and seasonings. Therefore, the effect of the MR on the volatile flavor compounds of SSF was investigated by HS-SPME-GC/MS in this work. A detailed study on the volatile flavor compounds of Shanghai smoked fish could not only enrich the theoretical knowledge of flavor chemistry of freshwater fish, but have a profound contribution to the development of freshwater fish processing techniques.

Black rice addition prompted the beer quality by the extrusion as pretreatment

Flavor compounds, including total polyphenols, amino acids, and protein, in beer with extruded black rice as adjunct were detected and analyzed. Beer brewing technique has been intensively investigated in the past century. The chase of beer quality, including the color, flavor, foam, nutrition, and functionality, attracted considerable attention. Hence, headspace solid-phase microextraction in combination with a gas chromatography coupled to mass spectrometry (HS-SPME-GC-MS) was used to analyze flavor compounds qualitatively and quantitatively. A total of one organic acid, one aromatic, ten alcohols and 23 esters were present in extruded black rice adjunct beer. Protein components and molecular weight were analyzed, and the results were consistent with those of traditional beer in terms of content of foam-stabilizing protein. The contents of essential amino acid which is an important nutritive index were higher than those in traditional rice adjunct beer, especially valine (70.9 mg/L) and threonine (42.8 mg/L). The representative ingredients of extruded black rice adjunct beer were polyphenols, nerolidol, geraniol, and geranylgeraniol which affected the functionality and antioxidant ability.