Identification of volatile compounds and metabolic pathway during ultrasound-assisted kombucha fermentation by HS-SPME-GC/MS combined with metabolomic analysis

Exploiting agri-food residues for kombucha tea and bacterial cellulose production

Bio-valorization of agri-food wastes lies in their possible conversion into fermented foodstuffs/beverages and/or biodegradable polymers such as bacterial cellulose. In this study, three different kombucha cultures were formulated using agri-food waste materials, citrus fruit residues and used coffee grounds, as alternative carbon and nitrogen sources, respectively. Over 21 days of fermentation, the kinetic profile was followed by monitoring cell density, pH variation, minerals, trace elements and production of bacterial cellulose. Moreover, the total phenolic and radical scavenging capacity was measured by spectrophotometric tests on the beverage and bacterial cellulose. Several classes of compounds were detected by gas chromatography coupled with mass spectrometry performing extractions on the headspace above fresh kombucha beverages and their lyophilized fractions, using solid phase micro extraction and liquid phase extraction, respectively. The obtained results allowed assessing molecular profiles of each kombucha beverages. A chemometric meta-analysis of the data revealed the individual impacts of the single ingredients and the effects of the fermentation process.

Thai Cannabis sativa Leaves as a Functional Ingredient for Quality Improvement and Lactic Acid Bacterial Growth Enhancement in Kombucha

Kombucha is a well-known fermented drink that gained interest due to its gut health benefits. However, it has a harsh taste of acetic acid and is hard to consume. Thai Cannabis leaves (Cannabis sativa sp. Hang Kra Rog Phu phan ST1) contain high protein and phytochemicals which can improve the growth of lactic acid bacteria (LAB) and enhance the organoleptic quality of the Kombucha. This study revealed the effect of infusing assam green tea leaves with cannabis leaves on the fermentation rate, microbial communities, volatile compounds, and overall quality and taste of the kombucha. The high protein content (23.10%) of Cannabis leaves was found. Phytonutrients and phytochemicals found in the leaves promotes LAB growth, which resulted in the higher number of LAB in the treatment with cannabis leaves. At the end of fermentation (day 7), the highest LAB count (5.53 log CFU mL-1) was presented in kombucha infused with 30% cannabis leaves. Kombucha with better quality, higher pH, and less acidity was obtained in a dose manner. The change in microbial communities was detected using metagenomic analysis. The prominence of Dekkera and Komagataeibacter, with low abundance of Zygosaccharomyces and Weissella were identified. These microorganisms improved flavor by lessening strong fermented odor and harsh acidic taste. From volatile compounds, HS-SPME-GCMS revealed that kombucha infused with 30% cannabis leaves possessed less acetic acid, ethanol, and carbon dioxide and gave a better odor and taste. Hence, cannabis leaves was the novel substrate for kombucha fermentation by enhancing LAB growth and improving the overall qualities.

Revealing differences in flavor compounds during plum wine fermentation using single and mixed yeast strains through metabolomic analysis

Mixed fermentation can enhance the flavor and aroma of fruit wine, but the mechanisms driving this enhancement remain unclear. This study used non-targeted metabolomics to analyze the effects of mixed versus single fermentation on plum wine flavor. The results showed that compared with single fermentation, mixed fermentation reduced ethanol content and the ability to consume reducing sugars. In single fermentation, volatile compounds increased over time, while in mixed fermentation, they first increased and then declined. Mixed fermentation notably increased esters and reduced higher alcohols, with key differentiators including phenethyl acetate, hexyl acetate, isoamyl acetate, ethyl acetate, isoamyl alcohol, phenethyl alcohol, ethyl caproate, and isobutanol. Furthermore, 40 differential non-volatile flavor compounds were identified, with amino acids emerging as the predominant differentiators. The annotation analysis of these compounds revealed 11 important metabolic pathways for proline, aspartate, glutamate, and β-alanine metabolism. These findings provide insight about producing plum wines with distinct flavor profiles.

Chemical, microbial, and functional characterization of a new fruity probiotic kombucha

This study aimed to evaluate the effect of adding Lacticaseibacillus casei as probiotic culture and/or camu-camu (Myrciaria dubia) pulp on the chemical profile, technological, functional, and sensory properties, phenolics concentration and bioaccessibility, and microbiota of kombucha. Adding L. casei decreased some volatile compounds and fruity flavor intensity and increased the Lactobacillus relative abundance (+35.73 %) and lactic acid content (from 1.26 to 1.54 g/L), decreasing flavor and overall impression acceptances. Adding camu-camu pulp resulted in more acidic products (pH of 2.75 vs 3.24), with a higher concentration of some phenolic compounds. The kombucha with L. casei and camu-camu pulp was characterized by a higher concentration of citric and acetic acids, ethanol, ascorbic acid, and most of the phenolic compounds and volatile compounds, higher bioaccessibility of phenolic compounds, increased consistency index, improved functional properties (inhibition of α-glucosidase and antioxidant activity), and better sensory properties. Furthermore, it showed an increased relative abundance of Lactobacillus (+15.11 %) and a decreased relative abundance of Acetobacter (-5.56 %) and Komagataeibacter (-9.12 %) compared to the conventional kombucha. L. casei survived the processing (> 7 log CFU/mL) and simulated gastrointestinal conditions (>5 log CFU/mL). In conclusion, the association of L. casei and camu-camu pulp resulted in potentially probiotic kombuchas with improved chemical profile, functional, technological, and sensory properties, phenolic compounds concentration and bioaccessibility, and bacterial microbial diversity.

Non-Targeted Metabolomics Analysis of γ-Aminobutyric Acid Enrichment in Germinated Maize Induced by Pulsed Light

Pulsed light is an emerging technique in plant physiology recognized for its ability to enhance germination and accumulate γ-aminobutyric acid in maize. Pulsed light involves exposing plants to brief, high-intensity bursts of light, which can enhance photosynthesis, improve growth, and increase resistance to environmental stresses. Despite its promising potential, the specific metabolic changes leading to γ-aminobutyric acid enrichment in maize induced by pulsed light are not fully understood. This study addresses this gap by quantifying key nutrients and γ-aminobutyric acid-related compounds during maize germination and investigating the underlying mechanisms using non-targeted metabolomics. Our findings indicate that pulsed light significantly promotes maize germination and accelerates the hydrolysis of proteins, sugars, and lipids. This acceleration is likely due to the activation of enzymes involved in these metabolic pathways. Additionally, pulsed light markedly increases the content of glutamic acid and the activity of glutamate decarboxylase, which are crucial for γ-aminobutyric acid synthesis. Moreover, pulsed light significantly reduces the activity of γ-aminobutyric transaminase, thereby inhibiting γ-aminobutyric acid decomposition and resulting in a substantial increase in γ-aminobutyric acid content, with a 27.20% increase observed in germinated maize following pulsed light treatment. Metabolomic analysis further revealed enrichment of metabolic pathways associated with γ-aminobutyric acid, including amino acid metabolism, carbohydrate metabolism, plant hormone signal transduction, energy metabolism, pyrimidine metabolism, and ABC transporters. In conclusion, pulsed light is a robust and efficient method for producing sprouted maize with a high γ-aminobutyric acid content. This technique provides a novel approach for developing sprouted cereal foods with enhanced nutritional profiles, leveraging the physiological benefits of γ-aminobutyric acid, which include stress alleviation and potential health benefits for humans.

Detection of Maize Mold Based on a Nanocomposite Colorimetric Sensor Array under Different Substrates

This study developed a novel nanocomposite colorimetric sensor array (CSA) to distinguish between fresh and moldy maize. First, the headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) method was used to analyze volatile organic compounds (VOCs) in fresh and moldy maize samples. Then, principal component analysis and orthogonal partial least-squares discriminant analysis (OPLS-DA) were used to identify 2-methylbutyric acid and undecane as key VOCs associated with moldy maize. Furthermore, colorimetric sensitive dyes modified with different nanoparticles were employed to enhance the dye properties used in the nanocomposite CSA analysis of key VOCs. This study focused on synthesizing four types of nanoparticles: polystyrene acrylic (PSA), porous silica nanospheres (PSNs), zeolitic imidazolate framework-8 (ZIF-8), and ZIF-8 after etching. Additionally, three types of substrates, qualitative filter paper, polyvinylidene fluoride film, and thin-layer chromatography silica gel, were comparatively used to fabricate nanocomposite CSA combining with linear discriminant analysis (LDA) and K-nearest neighbor (KNN) models for real sample detection. All moldy maize samples were correctly identified and prepared to characterize the properties of the CSA. Through initial testing and nanoenhancement of the chosen dyes, four nanocomposite colorimetric sensitive dyes were confirmed. The accuracy rates for LDA and KNN models in this study reached 100%. This work shows great potential for grain quality control using CSA methods.

Ginger beer derived from back-slopping: Volatile compounds, microbial communities on activation and fermentation, metabolites and sensory characteristics

Physicochemical parameters, microbial diversity using sequencing and amplicon, and metabolite concentrations from Ginger Bug and Ginger Beer were characterized. Furthermore, the sensory aspects of the beverage were determined. The longer ginger bug activation time (96 h) resulted in higher production of organic acids and alcohols, increased phenolic and volatile compounds concentration, greater microbial diversity, and increased lactic acid bacteria and yeasts. In the same way, the longer fermentation time (14 days) of ginger beer resulted in higher ethanol content, volatile compounds, and phenolic compounds, in addition to better sensory characteristics. Our results showed that ginger beer produced with ginger bug and fermented for 14 days showed better volatile and phenolic compound profiles, physicochemical parameters, microbial diversity, and sensory characteristics.

Dynamic Changes in Microbial Communities, Physicochemical Properties, and Flavor of Kombucha Made from Fu-Brick Tea

In this study, Fu-brick tea (FBT) was used for kombucha preparation. The succession of microbial community structures, changes in physicochemical properties, and the volatiles were investigated during the kombucha fermentation. The sequencing analysis showed that Komagataeibacter was the most predominant bacterium. Aspergillus and Zygosaccharomyces were the dominant fungi before fermentation whereas Zygosaccharomyces and Derkella were the dominant fungi after 3 days of fermentation. The physicochemical analysis revealed that acetic acid, glucuronic acid, and polyphenols increased by 10.22 g/L, 0.08 g/L, and 177.40 mg/L, respectively, by the end of fermentation. The GC-MS analysis showed that a total of 49 volatile compounds were detected during the fermentation. Moreover, there were great differences in volatile components among the kombucha samples with different fermentation times. Furthermore, the relevance among microbial community and volatile compounds was evaluated through correlation network analysis. The results suggested that Komagataeibacter, Aspergillus, Zygosaccharomyces, and Dekkera were closely related to the main volatile compounds of FBT kombucha. The results in this study may provide deep understanding for constructing the microbiota and improving the quality of FBT kombucha.

Volatile compound dynamics in oats solid-state fermentation: A comparative study of Saccharomyces cerevisiae A3, Lactococcus lactis 4355, and Lactobacillus plantarum 2329 inoculations

Fermentation is a longstanding method that enhances food quality and finds extensive food processing and preservation applications. This study comprehensively studied the impact of oats fermentation by Saccharomyces cerevisiae A3 and Lactococcus lactis 4355 (T1), Saccharomyces cerevisiae A3, and Lactobacillus plantarum 2329 (T2) on volatile-compounds using UHPLC-MS/MS. A total of 74 volatile compounds were found in control samples (YM), 81 in T1 samples, and 60 in T2 samples. T2 samples showed the highest hydrocarbons, esters, and phenols (25.7%, 2.26%, and 0.32%) compared with T1 (21.6%, 1.29%, and 0.19%) and YM samples (18.6%, 1.86%, and 0), respectively. Moreover, volcano, Z-score scatter plot distributions, and KEGG-path analysis indicated that different metabolic pathways in YM-T1 and YM-T2 models, where glycerophospholipid-metabolic pathways were the dominant in T1, while ABC transporters-pathways were the prominent in T2. These findings offer valuable insights for future advancements of novel oat products with enhanced functionality.