Yong-Jin Jeong

Effect of Nuruk and Fermentation Method on Organic Acid and Volatile Compounds in Brown Rice Vinegar

The effects of different nuruk contents and fermentation methods (AV, vinegar fermented in an agitated culture; SV, vinegar fermented in a static culture) on organic acids and volatile compounds in brown rice vinegars were investigated. In the SV, the contents of acetic, oxalic, tartaric, and malic acids increased with hipher contents of nuruk. Acetic, tartaric, and malic acid contents were higher in the SV than those in the AV. Volatile compounds that can affect vinegar quality, including acetic acid, isoamyl acetate, phenethyl acetate, and phenethyl alcohol were present at high concentrations in the AV. With the increase in nuruk contents in the AV, acetic acid content decreased and isoamyl acetate and phenethyl acetate content increased. No significant differences in sensory scores were observed regarding the amount of nuruk and the type of fermentation. However, electronic-nose analysis showed its potential to effectively differentiate different samples.

Quality Comparison of Commercial Cider Vinegars by Their Acidity Levels

The quality of commercial cider vinegars was compared according to their acidity levels (low, general, double strength and triple strength). The pH, reducing sugar content and brown color intensity decreased, while the total acidity increased with the increasing acidity levels, which may be resulted from difference in formulation and manufacturing procedures. The free sugars were mainly composed of fructose and glucose, which were the highest in low acidity vinegar, followed by double strength, general, and triple strength acidity vinegars. Acetic acids and malic acids were identified as the major organic acids. The citric acid concentration was the highest in triple strength vinegars. The contents of total phenolics and flavonoids were the highest in low acidity vinegars, which indicated their dependence on the apple juice content. DPPH and ABTS radical scavenging abilities were the highest in low acidity vinegars, that showed high amounts of antioxidants.

Effect of Nuruks and Crude Amylolytic Enzyme on Free Amino Acid and Volatile Components of Brown Rice Vinegar Prepared by Static Culture

The effect of nuruks and crude amylolytic enzyme on free amino acid and volatile components of brown rice vinegar prepared by static cultures was investigated. Five groups consisted of AV (100% nuruk without crude amylolytic enzyme), BV (75% nuruk; 25% crude amylolytic enzyme), CV (50% nuruk; 50% crude amylolytic enzyme), DV (25% nuruk; 75% crude amylolytic enzyme) and EV (100% crude amylolytic enzyme without nuruk). Free amino acid content in AV vinegar (132.06 mg%) was lower than the others (184.56-191.22 mg%). Acetic acid, 3-methyl butyl acetate, acetoin and isoamyl alcohol were major volatile components as analyzed using gas chromatography-mass spectrometry after headspace solid-phase microextraction. Acetic acid in AV and EV samples represented 67.56% and 55.53% of total GC peak area, respectively. E-nose provided different patterns in each case showing variation in sensory properties.The effect of nuruks and crude amylolytic enzyme on free amino acid and volatile components of brown rice vinegar prepared by static cultures was investigated. Five groups consisted of AV (100% nuruk without crude amylolytic enzyme), BV (75% nuruk; 25% crude amylolytic enzyme), CV (50% nuruk; 50% crude amylolytic enzyme), DV (25% nuruk; 75% crude amylolytic enzyme) and EV (100% crude amylolytic enzyme without nuruk). Free amino acid content in AV vinegar (132.06 mg%) was lower than the others (184.56-191.22 mg%). Acetic acid, 3-methyl butyl acetate, acetoin and isoamyl alcohol were major volatile components as analyzed using gas chromatography-mass spectrometry after headspace solid-phase microextraction. Acetic acid in AV and EV samples represented 67.56% and 55.53% of total GC peak area, respectively. E-nose provided different patterns in each case showing variation in sensory properties.

Analysis of aroma compounds of commercial cider vinegars with different acidities using SPME/GC-MS, electronic nose, and sensory evaluation

Aroma compounds of commercial cider vinegars according to their acidity (low, moderate, double-strength, and triple-strength) were comparatively investigated. SPME/GC-MS analysis revealed 8 types of aroma compounds commonly existing in the vinegar including acetic acid. A cider vinegar with moderate acidity showed the most volatile profiles. Electronic nose analysis suggested that the peak at 0.40 s was a component related to total acidity of vinegar. Principal component analysis enabled e-nose to discriminate easily by presenting the separated position depending on total acidity. Significant differences with the acidity were observed in the pungent odor intensity and odor preference. According to the results, the moderate acidity vinegar was revealed to retain most volatile profiles and sensory odor. Compared to sensory evaluation, the analysis using SPME/GC-MS and e-nose provided more distinct patterns on their volatile compounds depending on their acidity, which might be a potential tool in determining the volatile profiles of cider vinegars.

Physicochemical properties and volatile components of wine vinegars with high acidity based on fermentation stage and initial alcohol concentration

High acidity vinegar using grape concentrate was manufactured by fed-batch fermentation without additional chemical nutrients. Physicochemical properties and volatile components were investigated at different wine vinegar fermentation stages (stages 1–4) and at different initial alcohol concentrations (IAC, 6–9%). Acetic acid production showed a high yield and a rapid increase with an IAC=6%. The contents of reducing sugar, free amino acids, total phenolics, and overall volatiles increased during stage 4 (high acidity vinegar) most likely due to addition of a feeding solution. High acidity vinegar produced using a fed-batch culture at an IAC of 6% is a source of functional constituents with improved physicochemical and volatile properties, compared to moderate acidity vinegar.

Characteristics of Alcohol Fermentation of Citrus Fruit Hydrolysates

The present study investigated the alcohol fermentation characteristics of citrus fruit hydrolysates for the development of citrus fruit wine with enhanced functionality. The alcohol content of whole citrus (A) and removed peels citrus fruit (B) was 10.13% and 10.83%, respectively. The sugar content of (A) was 12.98Brix, which was slightly higher than that of (B) (11.38Brix), but no significant difference in the alcohol fermentation characteristics was observed. Although the hesperidin content was not largely affected by removed peels the narirutin content of (A) was increased to 281.31 μM, which was significantly higher than that of (B) (199.05 μM). Thus, the whole citrus was used for fermentation. Investigation of alcohol fermentation characteristics based on yeast type found that the maximum alcohol content was 12.75% when S. bayanus EC-1118 was used. The alcohol content reached 12.40% at an initial acidity of 0.2%, but when the initial acidity was higher than 0.2%, the alcohol content was slightly decreased. At an initial sugar content of 22°Brix, the alcohol content was 11.65%, and the maximum alcohol content of 12.85% was observed when at an initial sugar content of 24 o Brix.

Physicochemical Qualities and Flavor Patterns of Traditional Chinese Vinegars Manufactured by Different Fermentation Methods and Aging Periods

Physicochemical properties of Fujian Yongchun aged vinegar (FYAV) and Shanxi mature vinegar (SMV) were compared in terms of the fermentation methods applied and aging periods (3, 5, 8, and 10 years), and combined E-nose/E-tongue analyses were performed to assess their flavors. Compared with submerged fermentation-derived FYAV, solid-state fermentation-derived SMV showed higher values of pH, brix, soluble solids, total phenolic content, and antioxidant activity, but not total acidity or total organic acids. Aging period resulted in an increase in pH, total phenolic content, and antioxidant activity. Principal component analysis based on E-tongue/E-nose analyses was performed to distinguish between the vinegars produced by different fermentation methods and under aging periods. Solid-state fermentation and an aging process were considered good techniques for vinegar brewing, considering the various organic acids and high levels of total phenolics and antioxidant activity.

Application of E-tongue, E-nose, and MS-E-nose for discriminating aged vinegars based on taste and aroma profiles

The combined approach of E-senses was undertaken to discriminate the taste and aroma profiles of aged vinegars, including Chinese Shanxi extra aged vinegar (EX, 5-8 years), Japanese black vinegar (BL, 1-5 years), and Italian balsamic vinegar (BA, 8-25 years). The principal component analysis plot for E-tongue revealed that EX, BL, and BA formed individual groups with clear distinctions. The volatile compounds detected in E-nose based on Kovats indices represented that a major component in all vinegars was matched to acetic acid, which showed a strong relationship with the aging period (R=0.8186−0.9998). The discriminant function analysis plot accompanied by the MS-E-nose indicated that more volatiles were produced during prolonged aging in cereal vinegar, whereas the aging process degraded volatile constituents in fruit vinegar. Categorization with respect to aging years was possible using both E-noses. The approach using E-senses indicated a better discrimination for distinguishing the complex sensory information in aged vinegars.

Characterization of Acetobacter pomorum KJY8 isolated from Korean traditional vinegar.

Acetobacter sp. strains were isolated from traditional vinegar collected in Daegu city and Gyeongbuk province. The strain KJY8 showing a high acetic acid productivity was isolated and characterized by phenotypic, chemotaxonomic, and phylogenetic inference based on 16S rRNA sequence analysis. The chemotaxonomic and phylogenetic analyses revealed the isolate to be a strain of Acetobacter pomorum. The isolate showed a G+C content of 60.8 mol%. It contained LL-diaminopimelic acid (LL-A2pm) as the cell wall amino acid and ubiquinone Q9 (H6) as the major quinone. The predominant cellular fatty acids were C18:1w9c, w12t, and w7c. Strain KJY8 grew rapidly on glucose-yeast extract (GYC) agar and formed pale white colonies with smooth to rough surfaces. The optimum cultivation conditions for acetic acid production by the KJY8 strain were 20°C and pH 3.0, with an initial ethanol concentration of 9% (w/v) to produce an acetic acid concentration of 8% (w/v).