Preparation and aroma analysis of Chinese traditional fermented flour paste

Research on microbial diversity and nutritional flavor formation of Xianju wheat paste

BACKGROUND

Xianju wheat paste, a traditional condiment in Hubei Province, China, possesses nutritional value and a distinctive taste profile. Nevertheless, there remains a dearth of comprehensive comprehension regarding the intricate interplay between the microbial population and its nutritional profile in Xianju wheat paste.

RESULTS

It was determined that Xianju wheat paste harbors predominant microbial genera such as Bacillus, Staphylococcus and Aspergillus. The findings from high-throughput sequencing analysis revealed the presence of 11 bacterial genera in Xianju wheat paste, with relative abundances exceeding 1%. These genera included Bacillus, Staphylococcus, Brevibacterium, Lactobacillus, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Enterobacteriaceae, Pantoea, Brachybacterium, Klebsiella, Escherichia-Shigella and Ochrobactrum. Furthermore, six fungal genera were identified with relative abundances greater than 1%, specifically Aspergillus, Zygosaccharomyces, Cutaneotrichosporon, Candida, Millerozyma and Rhizopus. The correlation analysis indicated a significant impact of the microbial community and nutritional flavor on the second phase of fermentation in Xianju wheat paste. The predominant bacterium Bacillus in Xianju wheat paste facilitated the production of free amino acids, whereas Staphylococcus exhibited a negative correlation with free amino acid levels. The quantity of volatile compounds in Xianju wheat paste progressively increased during fermentation, with the presence of typical aroma compounds 4-vinyl-2-methoxyphenol significantly associated with Bacillus. This indicated Bacillus notably enhanced the production of aromatic substances. Furthermore, a strong correlation was observed between Staphylococcus and the 18 volatile organic compounds, highlighting their substantial contribution to these aroma compounds.

CONCLUSION

This research indicates that the presence of microbial communities significantly contributes to the development of the nutritional flavor profile in Xianju wheat paste. © 2024 Society of Chemical Industry.

Effect of Peony (Paeonia ostii) Seed Meal Supplement on Enzyme Activities and Flavor Compounds of Chinese Traditional Soybean Paste during Fermentation

Peony seed meal (PSM) is the by-product obtained from peony seeds after oil extraction. In this study, PSM was incorporated into traditional koji-making, and its impacts on koji enzyme activities and flavor compounds in final products were investigated. In the process of koji fermentation, the optimal addition ratio of PSM to soybean was determined as 7:3. Under this ratio, the maximum enzyme activities of neutral protease, amylase, and glucoamylase were 1177.85, 686.58, and 1564.36 U/g, respectively, and the koji obtained was subjected to maturation. During post-fermentation, changes in the fermentation characteristics of the paste samples were monitored, and it was found that compared to the soybean paste without PSM, the enzyme activities maintained at a relatively good level. The PSM soybean paste contained a total of 80 flavor compounds and 11 key flavor compounds (OAV ≥ 1), including ethyl isovalerate, isovaleric acid, hexanal, phenylacetaldehyde, 3-Methyl-1-butanol 4-heptanone, 2-pentylfuran, methanethiol ester caproate, isoamyl acetate, 3-methyl-4-heptanone, and isovaleraldehyde. These findings could be used to improve the quality of traditional fermented paste, enrich its flavor, and simultaneously promote PSM as a valuable resource for fermented foods.

Study on volatile compounds formed from the thermal interaction of hydrolyzed vegetable proteins with reducing sugars

Hydrolyzed vegetable proteins (HVPs) are widely used food flavorings. This study investigated the volatiles formed in thermally reacted model systems containing HVPs (made from defatted soy, corn gluten, and wheat gluten) and reducing sugars (glucose and fructose). Three types of HVPs, which had different free amino acid compositions, generated qualitatively and quantitatively different volatile compounds. In the results of principal component analysis, each thermally reacted system could be distributed according to type of HVPs and sugars. Aldehydes and pyrazines highly correlated with glucose- and fructose-containing model systems, respectively. In particular, model systems containing soy HVPs showed higher contents of sugar-degraded compounds, such as maltol, furfuryl alcohol, and cyclotene. However, some Strecker aldehydes and nitrogen-containing heterocyclic compounds, whose formation required amino acids, were more abundant in model systems containing corn and wheat HVP.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01194-w.

Characterization of the key aroma compounds of a sweet rice alcoholic beverage fermented with Saccharomycopsis fibuligera

This study aims to examine the effect of the non-Saccharomyces yeast Saccharomycopsis fibuligera on the sensory quality and flavour characteristics of a sweet rice alcoholic beverage. The strain S. fibuligera was isolated from a traditional Chinese hand-made starter with the purpose to improving sweet rice wine fragrance. Here, sweet rice wines were produced by six combinations of three species of fermentation strains, including S. fibuligera, Rhizopus and Saccharomyces cerevisiae, for evaluation. The study results showed significant diversities within these rice wines based on indicators including the score of quantitative descriptive analysis and volatile variety and content as well as odour activity value (OAV). Quantitative results showed that 43 volatile compounds were identified by headspace-solid phase microextraction with gas chromatography-mass spectrometry among samples. Based on the principal component analysis and OAV calculation, the two samples (S-2 and S-3) fermented with S. fibuligera and Rhizopus possessed high scores and were distinguished from the others, and ethyl butanoate, ethyl hexanoate, β-phenylethyl alcohol and 1-octen-3-one with high OAVs were responsible for the key aroma of sweet rice wine fermented with S. fibuligera. Co-inoculating S. fibuligera, Rhizopus or/and S. cerevisiae generated more pleasant aroma compounds in a sweet rice alcoholic beverage than when inoculated individually.

Correlation between the Characteristic Flavour of Youtiao and Trans Fatty Acids Assessed via Gas Chromatography Mass Spectrometry and Partial Least Squares Regression Analyses

This study aimed to analyse trans fatty acid (TFA) levels and key volatile flavour substances in fried youtiao prepared using five common edible oils and the relationship between TFAs and key volatile flavour substances via partial least squares regression (PLSR) analysis. Total TFA levels were the highest on using rapeseed oil during frying (approximately 1.061 mg/g), probably owing to the high content of unsaturated fatty acids in rapeseed oil and their instability. In total, 22 key flavour substances were detected. Although the flavours differed with different oils, flavour compounds including 3-(methyl sulphide) propionic aldehyde, (E,E)-2,4-sebacedienal, nonaldehyde, and 3-hydroxy-2-butanone contributed to overall flavour. PLSR analysis revealed that C18:2, 9t12t is produced with (E)-2-hexenaldehyde and nonaldehyde. (E,E)-2,4-sebacedienal levels were positively correlated with those of C18:2, 9c12t and C18:2, 9t12c. Most aliphatic aldehydes and pyrazines yield C18:3, 9t12t15c TFAs. These results indicate the characteristic flavour profile of youtiao and promote the preparation of healthy fried food.

Influence of Lactobacillus brevis on metabolite changes in bacteria-fermented sufu

Sufu is a form of food derived from traditional Chinese fermented soybean. It has a unique flavor and contains abundant nutrients. With demands for healthy food on the rise, a higher level of sufu functionality is required. In fermentation of soybean-derived products, lactic acid bacteria (LAB) are widely used as an adjunct culture, which provides health benefits and enhances flavor of food. Among LAB, Lactobacillus brevis has the potential to generate γ-aminobutyric acid (GABA), which is well-known for its physiological functions. In this study, L. brevis was added to bacteria-fermented sufu to evaluate its impacts on sufu quality. Sufu was produced via co-inoculation with Bacillus subtilis and L. brevis (group A sufu) or a single inoculation with B. subtilis (group B sufu). Metabolite changes in the two groups during fermentation were investigated and physicochemical changes were observed. The results indicated that the addition of L. brevis increased the concentration of GABA and decreased the concentrations of histamine and serotonin. The concentrations of volatile compounds, such as esters and acids, especially 2-methyl-butanoic acid ethyl ester, as well as the concentrations of phenylethyl alcohol and 3-methyl-butanol were significantly higher in group A. Inoculation of L. brevis changed the metabolite profile of sufu and improved its functionality and safety of edibility. The current study explored the potential of applying L. brevis to the manufacture of bacteria-fermented sufu.

Correlation of Volatile Compounds and Sensory Attributes of Chinese Traditional Sweet Fermented Flour Pastes Using Hierarchical Cluster Analysis and Partial Least Squares-Discriminant Analysis

The aroma compositions, sensory attributes, and their correlations of various traditional Chinese sweet fermented flour pastes (SFFPs) were investigated. SFFPs, including LEEJ, LEEH, and XH6, showed high overall acceptance scores of 8.00, 8.21, and 7.50, respectively. Ninety-six volatile compounds were detected using solid-phase microextraction gas chromatography mass spectrometry. Hierarchical cluster analysis grouped SFFPs into three clusters according to their concentrations and compositions of volatile components. Partial least squares-discriminant analysis showed that volatile compounds, including ethyl phenylacetate, 5-methyl furfural, amyl cinnamal, ethyl myristate, decyl aldehyde, 1-phenylethyl acetate, 1-octen-3-ol, 3-buten-2-ol, butanoic acid, and caproaldehyde, were highly negatively correlated with saltiness, sourness, and bitterness, while they were positively correlated with sweetness, umami, richness, and acceptance. The obvious correlation between flavor profiles and sensory attributes could help online monitoring of SFFPs’ flavor quality during production.