Quality Of Vinegar Research Articles

Onion Vinegar Quality Evaluation and its Alleviate Oxidative Stress Mechanism in Caenorhabditis elegans Via SKN-1

Recently, there has been renewed interest in biorefining of agricultural onion into functional products. In this study, onion vinegar (OV) are prepared by a two-stage semi-continuous fermentation method, and its content of total flavonoids (3.01 mg/mL) and polyphenols (976.76 μg/mL) is superior to other commercial vinegars. OV possesses a high radical scavenging activity and enhances the antioxidant enzyme activities in vivo, alleviating intracellular oxidative stress in Caenorhabditis elegans. Treated by OV, the 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH·), diammonium 2,2′-azino-bis (3-ethylbenzo thiazoline-6-sulfonic acid) (ABTS+·) and 2-phenyl-4,4,5,5- tetramethylimidazoline-1-oxyl 3-Oxide (PTIO·) free radicals clearance rates are 88.76, 98.76 and 90.54%, respectively in vitro. Whereas the glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) enzyme activities in C. elegans reach 271.57, 129.26, and 314.68%, respectively. Using RNAi and RT-PCR, it has been further confirmed that OV modulates transcription factor SKN-1, the nuclear factor erythroid 2-related factor 2 (Nrf2) homologous, in C. elegans, enhancing the resistance of C. elegans against sodium arsenite stress. Lifespan analysis reveals that 1 mL OV extends the maximum lifespan of the nematode to 26 days. Evidence is presented which shows that OV increases the lifespan of C. elegans by activating the SKN-1 signaling pathway. Overall, the OV is a well functional condiment, enhancing the value-added of onion.

Co‐fermentation metabolism characteristics of apple vinegar with Acetobacter pasteurianus and Lactobacillus plantarum

In this study, the growth and metabolic characteristics of Acetobacter pasteurianus and Lactobacillus plantarum used in the co-fermentation of apple vinegar were investigated. The results revealed that L. plantarum had little effect on the growth of A. pasteurianus during the co-fermentation process. The carbon sources used by L. plantarum and A. pasteurianus for growth were glucose and ethanol, respectively. Free amino acids, organic acids, and acetoin were analyzed using an amino acid analyzer, high-performance liquid chromatography, and gas chromatography, respectively. The results indicated that L. plantarum contributed to the accumulation of free amino acids during co-fermentation. Lactic acid, a key flavor substance, was accumulated mainly by L. plantarum during co-fermentation and was partly transformed into acetoin by A. pasteurianus. The acetoin content was 0.77 mg/ml, which is about twice that observed during pure fermentation with A. pasteurianus. Therefore, L. plantarum can improve the quality of apple vinegar during co-fermentation. Novelty impact statement L. plantarum had little effect on A. pasteurianus growth during co-fermentation of apple vinegar. The free amino acid and organic acid content in apple vinegar increased considerably because of the growth and metabolism of L. plantarum. The metabolites from L. plantarum could also be used by A. pasteurianus to improve the production of flavor substances during co-fermentation.

Fates of the components in cotton stalk during the hydrothermal oxidative pretreatment and its relationship with the upgrading of biochar pellets and wood vinegar

In the present study, biochar pellets and wood vinegar are prepared from the cotton stalk (CS) through the densification and pyrolysis, and hydrothermal oxidative (HO) pretreatment (160–260 °C) is conducted to CS to upgrade the quality of biochar pellet and wood vinegar (WV). The results show that HO pretreatment can decompose the hemicellulose, amorphous cellulose, crystalline cellulose, and lignin at 160–230 °C, 160–200 °C, 200–260 °C, and < 200 °C, respectively. Therefore, the hemicellulose and cellulose (especially the crystalline cellulose) in CS are enriched at 160–180 °C and 160–200 °C respectively. Due to the enrichment of hemicellulose and cellulose, the organic compounds in WV increase dramatically after HO pretreatment, resulting in a significant increase in the density and acidity of WV. Furthermore, due to the enrichment of hemicellulose and cellulose, the biochar pellets exhibit more densified internal structures after HO pretreatment, contributing to a higher relaxation density, energy density, and compressive strength. Moreover, the biochar pellets exhibit better combustion performance and lower ash content after HO pretreatment at 160–180 °C. The CS sample pretreated at 180 °C is the best material for the production of biochar pellets and WV.

Comparison of Phenolic Profile of Balsamic Vinegars Determined Using Liquid and Gas Chromatography Coupled with Mass Spectrometry.

Balsamic vinegar is one of the best known and most popular types of vinegar, and it is a rich source of polyphenolic compounds. The quality of balsamic vinegar as well as the content of phenolic substances vary depending on the production method. In the present work, we have developed a method for comprehensive characterization of the content of phenolic compounds in balsamic vinegars based on the combination of gas chromatography (GC) and high-performance liquid chromatography (HPLC) coupled with mass spectrometric detection in single mode (MS) and tandem mode (MS/MS). In total, 14 samples of different types of balsamic vinegar were analyzed without difficulty in sample preparation. The separation conditions and detection parameters of HPLC-MS/MS were optimized and used for the determination of 29 phenolic compounds and 6 phenolic acids. The profile of phenolic compounds was completed by semi-quantitative analysis of volatile organic compounds using GC-MS after optimized headspace solid-phase microextraction. Gallic acid, protocatechuic acid, caffeic acid, and p-coumaric acid have been identified as the major phenolic compounds in balsamic vinegars.

The composition, physicochemical properties, antimicrobial and antioxidant activity of wood vinegar prepared by pyrolysis of Eucommia ulmoides Oliver branches under different refining methods and storage conditions

To enhance the quality of wood vinegar (WV), the WV prepared by pyrolyzing Eucommia ulmoides Oliver (EUO) branches at the temperature of 650 °C were refined by using different physicochemical methods. The crude WV was refined by ultra-low freezing and thawing (WVFT), charcoal adsorption (WVCA), and activated carbon adsorption (WVACA), respectively. Meanwhile, the chemical compositions, antimicrobial and antioxidant activity of the crude WV (WVC), the WV (WVS) prepared two years ago, and the photolysis WV (WVP) were investigated. The results showed that the WVFT obtained by ultra-low freezing and thawing method possessed better quality with pH of 3.45, density of 1.045 g/cm³ , refractive index of 26.85% and total organic acid of 11.00%. It was also found that WVFT had better inhibition rate of 83.33% against Bacterium prodigiosum, indication the excellent antibacterial activity. Moreover, WVFT had significant effect on scavenging rate (98.72%) for hydroxyl radicals. This research could offer some references for the refining methods of WV, and the WV was expected to be a potential candidate for materials of antioxidant and antimicrobial.

​Optimization of Fermentation Factors for Vinegar Preparation from Sugarcane Jaggery using Response Surface Methodology

Background: Vinegar, an acidic functional fermentation product and known for its diverse health benefits was developed using liquid jaggery. A study was conducted to standardize the method of vinegar production from liquid jaggery using two different sugarcane varieties viz., CoH160 and Co89003. Methods: The submerged fermentation of liquid jaggery was carried out using yeast Saccharomyces cerevisiae and vinegar was produced using Acetobacter aceti. For the computation analysis of an optimized solution, a central composite rotatable design was applied which constituted three variables temperature (°C), inoculum concentration (%) and incubation time (days) and its influence on acetic acid percent as an important response was studied using Response Surface Methodology. Overall, twenty experimental trials were conducted as well as assessed on the vinegar quality indexes. Result: Vinegar prepared with 7.5 per cent inoculum concentration, incubated for a fermentation period of 12.5 days at 28.5°C was selected due to maximum acetic acid concentration achieved ( greater than 3.5% (w/v). The optimized vinegar contained total soluble solids (4.55-4.75 °Brix), reducing sugar (0.26-0.29%), total sugars (2.7-2.8%), titratable acidity (4.72-5.10%), pH (4.28-4.52), ascorbic acid (17.64-19.97%), alcohol content (0.68-0.79%), acetic acid (3.52-3.83%) and total phenols (36.69-38.22 mg/100 ml). The liquid jaggery vinegar had a bright yellow- brown color, cane flavor and vinegar aroma. It was found organoleptically acceptable.

Fruits Vinegar: Quality Characteristics, Phytochemistry, and Functionality.

The popularity of fruits vinegar (FsV) has been increased recently as a healthy drink wealthy in bioactive compounds that provide several beneficial properties. This review was designed in the frame of valorization of fruits vinegar as a by-product with high value added by providing overall information on its biochemical constituents and beneficial potencies. It contains a cocktail of bioactive ingredients including polyphenolic acids, organic acids, tetramethylperazine, and melanoidins. Acetic acid is the most abundant organic acid and chlorogenic acid is the major phenol in apple vinegar. The administration of fruits vinegar could prevent diabetes, hypercholesterolemia, oxidative stress, cancer, and boost immunity as well as provide a remarkable antioxidant ability. The production techniques influence the quality of vinegar, and consequently, its health benefits.

Physicochemical parameters combined flash GC e-nose and artificial neural network for quality and volatile characterization of vinegar with different brewing techniques

Vinegar is a kind of traditional fermented food, there are significant variances in quality and flavor due to differences in raw ingredients and processes. The quality assessment and flavor characteristics of 69 vinegar samples with 5 brewing processes were analyzed by physicochemical parameters combined with flash gas chromatography (GC) e-nose. The evaluation system of quality and the detection method of flavor profile were established. 17 volatile flavor compounds and potential flavor differential compounds of each brewing process were identified. The artificial neural network (ANN) analysis model was established based on the physicochemical parameters and the analysis of flash GC e-nose. Although the physicochemical parameters were more intuitive in quality evaluating, the flash GC e-nose could better reflect the flavor characteristics of vinegar samples and had better fitting, prediction and discrimination ability, the correct rates of training and prediction of flash GC e-nose trained ANN model were 98.6% and 96.7%, respectively.

The Impact of Apple Variety and the Production Methods on the Antibacterial Activity of Vinegar Samples.

Apple vinegar is a natural product widely used in food and traditional medicine as it contains many bioactive compounds. The apple variety and production methods are two factors that play a major role in determining the quality of vinegar. Therefore, this study aims to determine the quality of apple vinegar samples from different varieties (Red Delicious, Gala, Golden Delicious, and Starking Delicious) prepared by three methods using small apple pieces, apple juice, and crushed apple, through determining the physicochemical properties and antibacterial activity of these samples. The antibacterial activity was studied against five pathogenic bacteria: Staphylococcus aureus, Klebsiella pneumonia, Escherichia coli (ATB: 57), Escherichia coli (ATB: 97), and Pseudomonas aeruginosa, using two methods, disk diffusion and microdilution, for determining the minimum inhibitory concentrations and the minimum bactericidal concentrations. The results of this study showed that the lowest pH value was 3.6 for Stark Delicious, obtained by liquid fermentation, and the highest acetic acid values were 4.7 and 4% for the vinegar of Red Delicious and Golden Delicious, prepared by solid fermentation, respectively. The results of the antibacterial activity showed considerable activity of apple vinegar on the tested strains. Generally, the Staphylococcus aureus strain appears less sensitive and Pseudomonas aeruginosa seems to be very sensitive against all samples, while the other strains have distinct sensitivities depending on the variety studied and the method used. A higher antibacterial activity was found in vinegar obtained by the apple pieces method and the Red Delicious variety, with a low MIC and MBC recorded, at 1.95 and 3.90 µL/mL, respectively. This study has shown that the choice of both apple variety and production method is therefore an essential step in determining and aiming for the desired quality of apple vinegar.

A Methodology Based on FT-IR Data Combined with Random Forest Model to Generate Spectralprints for the Characterization of High-Quality Vinegars.

Sherry wine vinegar is a Spanish gourmet product under Protected Designation of Origin (PDO). Before a vinegar can be labeled as Sherry vinegar, the product must meet certain requirements as established by its PDO, which, in this case, means that it has been produced following the traditional solera and criadera ageing system. The quality of the vinegar is determined by many factors such as the raw material, the acetification process or the aging system. For this reason, mainly producers, but also consumers, would benefit from the employment of effective analytical tools that allow precisely determining the origin and quality of vinegar. In the present study, a total of 48 Sherry vinegar samples manufactured from three different starting wines (Palomino Fino, Moscatel, and Pedro Ximénez wine) were analyzed by Fourier-transform infrared (FT-IR) spectroscopy. The spectroscopic data were combined with unsupervised exploratory techniques such as hierarchical cluster analysis (HCA) and principal component analysis (PCA), as well as other nonparametric supervised techniques, namely, support vector machine (SVM) and random forest (RF), for the characterization of the samples. The HCA and PCA results present a clear grouping trend of the vinegar samples according to their raw materials. SVM in combination with leave-one-out cross-validation (LOOCV) successfully classified 100% of the samples, according to the type of wine used for their production. The RF method allowed selecting the most important variables to develop the characteristic fingerprint (“spectralprint”) of the vinegar samples according to their starting wine. Furthermore, the RF model reached 100% accuracy for both LOOCV and out-of-bag (OOB) sets.

Evaluation of quality the pumpkin, wild plum, pear, cabbage traditional homemade vinegars using the spectroscopy and rheology methods

In this study, the quality evaluation of homemade pumpkin, pear, wild plum and cabbage vinegar produced by traditional methods was carried out using the ultraviolet (UV) spectroscopy, rheology technique and Fourier transform infrared (FTIR) spectroscopy method. The measurement of UV spectra, flow behaviours and infrared spectral fingerprints of all the vinegars were performed in the wavelength range of 190 nm to 600 nm, shear rate of 10−3 s−1 to 102 s−1 and wavenumber of 4200 c−1 to 400 cm−1 at room temperature, respectively. The quality of homemade vinegars was correlated with the UV spectra peaks, which took values with acetic acid and phenolic compound concentrations. It was determined that the absorption coefficient and optical energy gaps (Eg) which were caused by the release time, depends on the organic acids content. It was observed that the UV spectra and forbidden energy gaps of all the vinegars compatible with the Lambert-Beer-Bouguer and Tauc laws, respectively. The flow behaviour of homemade vinegars was consistent with the non-Newtonian flow, which is the signature behaviour of the dilatant (thickening) and pseudo-plastic (thinning) liquids. Moreover, it was determined that the spectral fingerprint peaks obtained from FTIR spectroscopy were caused by the mixture of acetic acid and water forming the structure of the vinegar. As a result of spectroscopy and rheological analyses, which yields compatible results with commercial tests, it is predicted that it can be safely used as health test.

“도초방” 의 제조 공정 개선을 통한 고산도 복숭아 식초 제조

According to the method described in the ancient literature “Imwonsipyukji”, ‘Dochobang’ was mainly composed of lactic acid (756.81 mg/100 mL) and acetic acid (473.66 mg/100 mL) as the main organic acids on the 14th day of fermentation. The acidity of ‘Dochobang’ was 1.09%, resulting in low marketability. Therefore, this study aimed to improve the manufacturing process of peach vinegar and optimize the conditions, including temperature and initial pH, for producing high-acidity vinegar using fermented seeds. We first selected yeasts (Saccharomyces cerevisiae YM27) with excellent alcohol fermentation ability and acetic acid bacteria (Acetobacter oryzifermentans (KACC19301)) with remarkable acid-producing ability and used these in the process-improved two-stage fermentation. The experiment was conducted by 3 treatments of tepmerature(20°C, 30°C and 35°C) and initial pH(3, 4 and 5) for acetic acid fermentation. ‘Dochobang’ fermented alcohol and acetic acid at the same time by natural fermentation. on the other hand, peach wine starter and seed vinegar were added before each fermentation step to increase acetic acid production. Wines fermented at 25°C and 30°C were found to be 9% alcoholic on days sixth and nine days, respectively. Organic acid analysis revealed that the level of acetic acid in vinegar fermented at pH 4 and 20°C increased steadily until day 14 (6,171.3 mg/100 mL). The acidity was 7% on the 21st day of fermentation. Furthermore, as the fermentation progressed, the umami and sourness of the peach vinegar increased. We expect that our findings could improve the quality of peach vinegar recorded in the old literature and can be used in small-scale agricultural companies.

Chemical characterization of wood vinegar from acacia barks

The pyrolysis process was conducted into a low heating rate of 400 °C using a pyrolysis reactor. It was made of stainless steel, covered by fire clay bricks, and used electrical heating. Acacia barks were pyrolyzed for six hours. The chemical characteristics of wood vinegar produced from Acacia mangium bark were done by means of titration method, UV - VIS spectrophotometer, gas chromatography-mass spectrometry (GC-MS) analysis. The organic acid and phenol were analyzed to determine the quality of wood vinegar. The chemical components of wood vinegar were identified by GC-MS. The carbonation process produced charcoal, wood vinegar, gas, and tar, i.e., 66.33; 21.45; 12.16, and 0.06%, respectively. Wood vinegar has a brown color, a specific gravity of 1.0064, and a viscosity of 12-49 1 mPa·s at 60 rpm of the spindle. The major components of wood vinegar were acetic acid (47.36%) and phenolic compounds (18.96%), while tar was dominated by pentanoic acid (90.29%).

Metaproteomics of microbiota involved in submerged culture production of alcohol wine vinegar: A first approach

Acetic acid bacteria form a complex microbiota that plays a fundamental role in the industrial production of vinegar through the incomplete oxidation reaction from ethanol to acetic acid. The organoleptic properties and the quality of vinegar are influenced by many factors, especially by the raw material used as acetification substrate, the microbial diversity and the technical methods employed in its production. The metaproteomics has been considered, among the new methods employed for the investigation of microbial communities, since it may provide information about the microbial biodiversity and behaviour by means of a protein content analysis. In this work, alcohol wine vinegar was produced through a submerged culture of acetic acid bacteria using a pilot acetator, operated in a semi-continuous mode, where the main system variables were monitored and the cycle profile throughout the acetification was obtained. Through a first approach, at qualitative level, of a metaproteomic analysis performed at relevant moments of the acetification cycle (end of fast and discontinuous loading phases and just prior to unloading phase), it is aimed to investigate the microbiota existent in alcohol wine vinegar as well as its changes during the cycle; to our knowledge, this is the first metaproteomics report carried out in this way on this system. A total of 1723 proteins from 30 different genera were identified; 1615 out of 1723 proteins (93.73%) belonged to the four most frequent (%) genera: Acetobacter, Gluconacetobacter, Gluconobacter and Komagataeibacter. Around 80% of identified proteins belonged to the species Komagataeibacter europaeus. In addition, GO Term enrichment analysis highlighted the important role of catalytic activity, organic cyclic compound binding, metabolic and biosynthesis processes throughout acetic acid fermentation. These findings provide the first step to obtain an AAB profile at omics level related to the environmental changes produced during the typical semi-continuous cycles used in this process and it would contribute to the optimization of operating conditions and improving the industrial production of vinegar.

Pengaruh Penambahan Ragi Tape dan Waktu Fermentasi Hasil Samping Cairan Pulpa terhadap Karakteristik Mutu Cuka Kakao (Theobroma cacao L.)

The aim of this study was to determine the effect of adding ragi tape and the time of natural fermentation of the pulp byproducts of the fermented cocoa beans on the characteristics of the quality of cocoa vinegar and determining the addition of tape yeast and the natural fermentation time of the best pulp fluid for cocoa vinegar production. The experiments in this study used a randomized block design with two factors. The first factor is the addition of yeast tape consisting of 5 levels, namely without the addition of yeast tape (control), the addition of yeast tape 0.05% (w / v), 0.10% (w / v), 0.15% (w / v), 0.20% (w / v), the second factor is the fermentation time consisting of 6 levels, namely 5, 10, 15, 20, 25, 30 days. Treatment The addition of tape yeast has a very significant effect on acetic acid, pH, total dissolved solids, total sugar, has no significant effect on alcohol content in the fermented vinegar from the pulp fluid which is the by-product of cocoa bean fermentation. The length of fermentation treatment has a very significant effect on acetic acid, pH, total dissolved solids, total sugar, alcohol. The interaction between the two treatments had no significant effect on acetic acid, pH, total dissolved solids, alcohol content, and significant effect on total sugar in fermented cocoa vinegar products. The best treatment was obtained from the addition of 0.15% (w / v) yeast tape and 30 days fermentation time which produced cacao vinegar with acetic acid content of 2.40%, pH 3.37, total dissolved solids 4.25 obrix, total sugar 0.03%, and 0.00% alcohol.&#x0D; Keywords : vinegar fermentasion, ragi tape, time of fermentation

Production of coco-vinegar in a bubble biofermentor

The economic value of coconut water can be increased through its conversion into a functional drink of coco vinegar powder having antioxidant and anti-diabetic properties. The fermentation of coconut water into coco-vinegar is more beneficial and cheaper than the chemical routes. Nevertheless, to guarantee product stability and increase the fermentation rate, the fermentation process must be controlled. Bubble bio-fermentation is an applicative technique in upgrading the production scale and in preserve the coco vinegar quality due to its unique characteristics i.e.: simple design, fixed part, controlled flow and agitation, uniform space-time, larger contact area, lower energy input, larger capacity, and higher mass transfer rate. This research objective was to investigate the influence of the parameter process i.e. sugar and alcohol concentration towards the formation of acetic acid in the coconut water fermentation. The research showed that bubble fermentation of coconut water was proven as a potential method for the coco vinegar production process. The bubble bio-fermentation of coconut water conducted by the addition of 8% of sugar, 10% of ethanol and 15% of Acetobacteracetii inoculum and fermentation process for 21 hours was able to give a vinegar having acetic acid concentration up to 1.04%.

Classification of Chinese vinegar varieties using electronic nose and fuzzy Foley-Sammon transformation.

Due to the difference of raw materials and brewing technology, the quality and flavours of vinegar are different. Different kinds of vinegar have different functions and effects. Therefore, it is important to classify the vinegar varieties correctly. This work presented a new fuzzy feature extraction algorithm, called fuzzy Foley-Sammon transformation (FFST), and designed the electronic nose (E-nose) system for classifying vinegar varieties successfully. Principal component analysis (PCA) and standard normal variate (SNV) were used as the data preprocessing algorithms for the E-nose system. FFST, Foley-Sammon transformation (FST) and linear discriminant analysis (LDA) were used to extract discriminant information from E-nose data, respectively. Then, K nearest neighbor (KNN) served as a classifier for the classification of vinegar varieties. The highest identification accuracy rate was 96.92% by using the FFST and KNN. Therefore, the E-nose system combined with the FFST was an effective method to identify Chinese vinegar varieties and this method has wide application prospects.

Changes of Physicochemical, Bioactive Compounds and Antioxidant Capacity during the Brewing Process of Zhenjiang Aromatic Vinegar.

Zhenjiang aromatic vinegar (ZAV) is a kind of traditional fermented food worldwide. In this study, the changes of physicochemical properties, total phenolic content (TPC), total flavonoid content (TFC), and total antioxidant activity (TAA) were evaluated during the brewing process of ZAV. In addition, the correlation between phenolic compound contents and antioxidant activities was investigated during the aging process (AP) of ZAV. The results showed that total acids, non-volatile acids, and amino nitrogen increased gradually during the brewing process. Reducing sugar decreased sharply at the early fermentation stage and then increased during the AP. Meanwhile, TPC, TFC, and TAA kept a very low level at the stage of alcohol fermentation (AF), and increased to the highest level at the sixth year of the AP. TAA has a high positive correlation with TPC and TFC during the brewing process of ZAV. In addition, the contents of p-hydroxybenzoic acid, vanillic acid, and catechin were higher than other phenolic compounds and reached the highest level at the sixth year of the AP, and were the main composition of phenolic compounds during the AP. Moreover, gallic acid, ferulic acid, and sinapic acid had the higher contribution at the early stage of the AP, and then declined to a lower level. Catechin, vanillic acid, and syringic acid had a higher contribution during the AP. These findings would be helpful in controlling the quality of vinegar and improving its functional properties.

Effect of α-Amylase and Glucoamylase Enzymes on Chemical Qualities of Vinegar from Banana Peel

The rate of banana consumption in Indonesia is reported to be increased. Abundant banana peels causes environmental problem. Peels of banana still have the potential to be utilized in the making of vinegar. Banana peels have high contents of fiber and carbohydrate, however breakage of polysaccharide bonds with enzyme is necessary. The α-amylase and glucoamylase are suitable enzymes to optimally break the polysaccharide bonds. The objective of this research was to determine the effect of α-amylase and glucoamylase on chemical qualities of banana-peel vinegar. The experimental design used was a Block Randomized Design with two factors and three replications. The ‘A’ factor was concentration of α-amylase at three levels (0.05%; 0.1%; 0.15%). The ‘B’ factor was concentration of glucoamylase at two levels (0.1%; 0.15%). Observation parameters included reducing-sugar, concentration of alcohol and acetic acid, and pH values. The high level of acetic acid was obtained from A2B1 (0.10% α-amylase; 0.10% glucoamylase) with an average value of 4.05% and pH of 3.52 on day-30 of fermentation period. An average value of reducing-sugar level on day-1 was 0.55% (g/ml) accompanied by alcohol content reduction of 0.386%. The best quality of banana-peel vinegar was resulted from the A2B1 treatment (0.10% α-amylase, 0.10% glucoamylase). Good quality vinegar was characterized by its aqueous liquid form, acetic acid odor with level at least 4%, residual alcohol at maximum level of 10%. The study has implications for the utilization of banana peel waste as natural preservatives.

Microbial dynamics and flavor formation during the traditional brewing of Monascus vinegar.

Monascus vinegar is one of the most famous and popular Chinese vinegars. The present study identified 60 volatile compounds, 23 amino acids, and seven organic acids during the traditional brewing of Monascus vinegar. Acetic acid, alanine, alcohols, esters, lactic acid, and valine were the predominant metabolic compounds found during the fermentation process. Komagataeibacter medellinensis, Lactobacillus acetotolerans, Saccharomycopsis fibuligera, Sterigmatomyces halophilus, and Yarrowia lipolytica were the dominant microorganisms during the traditional brewing of Monascus vinegar. Furthermore, based on Spearman's correlation analysis, K. medellinensis showed a positive correlation with acetic acid, acetoin, benzaldehyde, phenethyl acetate, 4-ethylphenol, proline, threonine, and isoleucine. Saccharomyces cerevisiae was positively associated with the production of acetoin, benzeneacetaldehyde, 2,3,5-trimethylpyrazine, proline, threonine, and isoleucine. Bacillus velezensis and Yarrowia lipolytica were positively correlated with esters and alcohols, implying that these microorganisms might make a significant contribution to the flavor of vinegar. These findings demonstrated that some microorganisms may play important roles in improving the aromatic quality of Monascus vinegar.