HS-SPME-GC × GC/MS combined with multivariate statistics analysis to investigate the flavor formation mechanism of tank-fermented broad bean paste

Exploring the influence and mechanism of different frying methods on the flavor quality of low-salt sour meat

To obtain nutritious, healthy, and flavor-enriched sour meat products, the effects of different frying methods (microwave, air-frying, and traditional frying) on the flavor quality of low-salt sour meat were evaluated using metabolomics and other flavor analysis techniques. The pH value of the sour meat rose dramatically, while the TBARS value dropped significantly after frying. E-nose and E-tongue results showed that air-frying could reduce acidity and improve umami. The comprehensive analysis of all samples revealed the identification of 107 volatile flavor compounds, including 10 unique aroma compounds that were specifically detected in the AF group. Additionally, the air frying process notably increased the free amino acid and nucleotide concentrations in sour meat by 53.58% and 159.29%, respectively, while causing a significant reduction in both fatty acid and lactic acid content by 22.84% and 49.29%, respectively. All three frying methods altered the flavor of the samples, but air frying performed better in terms of flavor and texture.

Investigation into the potential mechanism of Bacillus amyloliquefaciens in the fermentation of broad bean paste by metabolomics and transcriptomics

Pixian broad bean paste is a renowned fermented seasoning. The fermentation of broad bean is the most important process of Pixian broad bean paste. To enhance the flavor of tank-fermented broad bean paste, salt-tolerant Bacillus amyloliquefaciens strain was inoculated, resulting in an increase in total amount of volatile compounds, potentially leading to different flavor characteristics. To investigate the fermentation mechanism, monoculture simulated fermentation systems were designed. Metabolomics and transcriptomics were used to explore Bacillus amyloliquefaciens' transcriptional response to salt stress and potential aroma production mechanisms. The results highlighted different metabolite profiles under salt stress, and the crucial roles of energy metabolism, amino acid metabolism, reaction system, transportation system in Bacillus amyloliquefaciens' hypersaline stress response. This study provides a scientific basis for the industrial application of Bacillus amyloliquefaciens and new insights into addressing the challenges of poor flavor quality in tank fermentation products.

Solid-phase microextraction coupled to comprehensive multidimensional gas chromatography for food analysis

Solid-phase microextraction and comprehensive multidimensional gas chromatography represent two milestone innovations that occurred in the field of separation science in the 1990s. They have a common root in their introduction and have found a perfect coupling in their evolution and applications. This review will focus on food analysis, where the paradigm has changed significantly over time, moving from a targeted analysis, focusing on a limited number of analytes at the time, to a more holistic approach for assessing quality in a larger sense. Indeed, not only some major markers or contaminants are considered, but a large variety of compounds and their possible interaction, giving rise to the field of foodomics. In order to obtain such detailed information and to answer more sophisticated questions related to food quality and authenticity, the use of SPME-GC × GC-MS has become essential for the comprehensive analysis of volatile and semi-volatile analytes. This article provides a critical review of the various applications of SPME-GC × GC in food analysis, emphasizing the crucial role this coupling plays in this field. Additionally, this review dwells on the importance of appropriate data treatment to fully harness the results obtained to draw accurate and meaningful conclusions.

Influence of lactic acid fermentation on the phenolic profile, antioxidant activities, and volatile compounds of black chokeberry (Aronia melanocarpa) juice

Lactic acid fermentation is an effective method for improving the quality of black chokeberry. This study aimed to investigate the influence of lactic acid bacteria on the phenolic profile, antioxidant activities, and volatiles of black chokeberry juice. Initially, 107  cfu/mL of Lactiplantibacillus plantarum, Lactobacillus acidophilus, and Lacticaseibacillus rhamnosus were inoculated into pasteurized black chokeberry juice and fermented for 48 h at 37°C. All these strains enhanced the total phenolic and total flavonoid contents, with La. acidophilus showing the highest total phenolic (1683.64 mg/L) and total flavonoid (659.27 mg/L) contents. Phenolic acids, flavonoids, and anthocyanins were identified using ultrahigh-performance liquid chromatography-tandem mass spectrometry. The prevalent phenolic acid, flavonoid, and anthocyanin in the lactic-acid-fermented black chokeberry juice were cinnamic acid, rutin, and cyanidin-3-O-rutinoside, respectively. Furthermore, following fermentation, the DPPH and ABTS scavenging capacity, as well as the reducing power capacity, increased from 59.98% to 92.70%, 83.06% to 94.95%, and 1.24 to 1.82, respectively. Pearson's correlation analysis revealed that the transformation of phenolic acids, flavonoids, and anthocyanins probably contributed to enhancing antioxidant activities and color conversation in black chokeberry juice. A total of 40 volatiles were detected in the fermented black chokeberry juice by gas chromatography-ion mobility spectrometry. The off-flavor odors, such as 1-penten-3-one and propanal in the black chokeberry juice, were weakened after fermentation. The content of 2-pentanone significantly increased in all fermented juice, imparting an ethereal flavor. Hence, lactic acid fermentation can effectively enhance black chokeberry products' flavor and prebiotic value, offering valuable insights into their production. PRACTICAL APPLICATION: The application of lactic acid bacteria in black chokeberry juice not only enhances its flavor but also improves its health benefits. This study has expanded the range of black chokeberry products and offers a new perspective for the development of the black chokeberry industry.

Effects of different drying methods on Rubus chingii Hu fruit during processing

In this study, the dried fruits of Rubus chingii Hu (Chinese name: Fu-Pen-Zi; FPZ) were processed and dried by three methods-in the shade, the sun, and the oven. The composition regarding the standard ingredient, color, and antioxidant capacities were investigated pro- and post-processing. The technique of headspace-solid-phase-microextraction-gas-chromatography-mass spectrometry (HS-SPME-GC-MS) and flavoromics were used to analyze the flavor-conferring metabolites of FPZ. The results obtained revealed that the highest use value and antioxidant capacities were detected in the FPZ fruits processed and dried in the shade. A total of 358 metabolites were detected from them mainly consisting of terpenoids, heterocyclic compounds, and esters. In differential analysis, the down-regulation of the metabolites was much greater than their up-regulation after all three drying methods. In an evaluation of the characteristic compounds and flavors produced after the three methods, there were variations mainly regarding the green and fruity odors. Therefore, considerable insights may be obtained for the development of novel agricultural methods and applications in the pharmaceutical and cosmetic industries by analyzing and comparing the variations in the chemical composition detected pre- and post-processing of the FPZ fruits. This paper provides a scientific basis for quality control in fruits and their clinical applications.

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.

Exploring metabolic dynamics during the fermentation of sea buckthorn beverage: comparative analysis of volatile aroma compounds and non-volatile metabolites using GC-MS and UHPLC-MS

Sea buckthorn has a high nutritional value, but its sour taste and foul odor make it unpalatable for consumers. In this study, we analyzed the metabolite changes occurring during the yeast-assisted fermentation of sea buckthorn juice using the HeadSpace Solid-Phase Microextraction Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS) and Ultra-High Performance Liquid Chromatography-Mass Spectrometry (UHPLC-MS) techniques. A total of 86 volatile aroma compounds were identified during the fermentation process. The content of total volatiles in sea buckthorn juice increased by 3469.16 μg/L after 18 h of fermentation, with 22 compounds showing elevated levels. Notably, the total content of esters with fruity, floral, and sweet aromas increased by 1957.09 μg/L. We identified 379 non-volatile metabolites and observed significant increases in the relative abundance of key active ingredients during fermentation: glycerophosphorylcholine (increased by 1.54), glutathione (increased by 1.49), L-glutamic acid (increased by 2.46), and vanillin (increased by 0.19). KEGG pathway analysis revealed that amino acid metabolism and lipid metabolism were the primary metabolic pathways involved during fermentation by Saccharomyces cerevisiae. Fermentation has been shown to improve the flavor of sea buckthorn juice and increase the relative content of bioactive compounds. This study provides novel insights into the metabolic dynamics of sea buckthorn juice following yeast fermentation through metabolomics analysis. These findings could serve as a theoretical foundation for further studies on the factors influencing differences in yeast fermentation.

Effects of degree of milling on nutritional quality, functional characteristics and volatile compounds of brown rice tea

This study investigated the effects of rice preparation using different degrees of milling (DOM) from 0% to 13% on the nutritional composition, functional properties, major volatile compounds and safety of brown rice tea (BRT). We found that 2% DOM reduced 52.33% of acrylamide and 31.88% of fluorescent AGEs. When DOM was increased from 0% to 13%, the total phenolic content (TPC) of brown rice tea decreased by 48.12%, and the total flavonoid content (TFC) and condensed tannin content (CTC) also decreased significantly, with the smallest decrease at 2% DOM. In addition, the inhibitory activities of α-amylase, α-glucosidase and pancreatic lipase as well as the antioxidant activity also decreased gradually. Analysis by electronic nose and gas chromatography-mass spectrometry (GC-MS) showed that alkanes, furans, aldehydes, pyrazines and alcohols were the major volatiles in BRT, with 2% DOM having the greatest retention of aroma compounds. An orthogonal partial least squares discriminant analysis (OPLS-DA) and VIP score (VIP > 1 and p < 0.05) analysis were used to screen 25 flavor substances that contributed to the differences in BRT aroma of different DOMs. These results suggest that 2% milled BRT can improve safety and palatability while maximizing the retention of flavor compounds and nutrients. The findings of this study contribute to an enhanced understanding of the dynamics of changes and preservation of aroma compounds and nutrients present during the processing of BRT.