Hong-Seok Son

Metabolomic studies on geographical grapes and their wines using 1H NMR analysis coupled with multivariate statistics.

Environmental vineyard conditions can affect the chemical composition or metabolites of grapes and their wines. Grapes grown in three different regions of South Korea were collected and separated into pulp, skin, and seed. The grapes were also vinified after crushing. (1)H NMR spectroscopy with pattern recognition (PR) methods was used to investigate the metabolic differences in pulp, skin, seed, and wines from the different regions. Discriminatory compounds among the grapes were Na, Ca, K, malate, citrate, threonine, alanine, proline, and trigonelline according to PR methods of principal component analysis (PCA) or partial least-squares discriminant analysis (PLS-DA). Grapes grown in regions with high sun exposure and low rainfall showed higher levels of sugar, proline, Na, and Ca together with lower levels of malate, citrate, alanine, threonine, and trigonelline than those grown in regions with relatively low sun exposure and high rainfall. Environmental effects were also observed in the complementary wines. This study demonstrates that (1)H NMR-based metabolomics coupled with multivariate statistical data sets can be useful for determining grape and wine quality.

1H Nuclear Magnetic Resonance-Based Metabolomic Characterization of Wines by Grape Varieties and Production Areas

(1)H NMR spectroscopy was used to investigate the metabolic differences in wines produced from different grape varieties and different regions. A significant separation among wines from Campbell Early, Cabernet Sauvignon, and Shiraz grapes was observed using principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA). The metabolites contributing to the separation were assigned to be 2,3-butanediol, lactate, acetate, proline, succinate, malate, glycerol, tartarate, glucose, and phenolic compounds by PCA and PLS-DA loading plots. Wines produced from Cabernet Sauvignon grapes harvested in the continental areas of Australia, France, and California were also separated. PLS-DA loading plots revealed that the level of proline in Californian Cabernet Sauvignon wines was higher than that in Australian and French Cabernet Sauvignon, Australian Shiraz, and Korean Campbell Early wines, showing that the chemical composition of the grape berries varies with the variety and growing area. This study highlights the applicability of NMR-based metabolomics with multivariate statistical data sets in determining wine quality and product origin.

1H NMR-based metabolomic approach for understanding the fermentation behaviors of wine yeast strains.

(1)H NMR spectroscopy coupled with multivariate statistical analysis was used for the first time to investigate metabolic changes in musts during alcoholic fermentation and wines during aging. Three Saccharomyces cerevisiae yeast strains (RC-212, KIV-1116, and KUBY-501) were also evaluated for their impacts on the metabolic changes in must and wine. Pattern recognition (PR) methods, including PCA, PLS-DA, and OPLS-DA scores plots, showed clear differences for metabolites among musts or wines for each fermentation stage up to 6 months. Metabolites responsible for the differentiation were identified as valine, 2,3-butanediol (2,3-BD), pyruvate, succinate, proline, citrate, glycerol, malate, tartarate, glucose, N-methylnicotinic acid (NMNA), and polyphenol compounds. PCA scores plots showed continuous movements away from days 1 to 8 in all musts for all yeast strains, indicating continuous and active fermentation. During alcoholic fermentation, the highest levels of 2,3-BD, succinate, and glycerol were found in musts with the KIV-1116 strain, which showed the fastest fermentation or highest fermentative activity of the three strains, whereas the KUBY-501 strain showed the slowest fermentative activity. This study highlights the applicability of NMR-based metabolomics for monitoring wine fermentation and evaluating the fermentative characteristics of yeast strains.

Metabolomic Characterization of Malolactic Fermentation and Fermentative Behaviors of Wine Yeasts in Grape Wine

Wine contains a number of metabolites that are produced during alcoholic and malolactic fermentations (MLF) or aging, which are important compounds for determining wine quality. This study investigated changes in metabolites in wines to characterize malolactic fermentation (MLF) and to assess fermentative behaviors of wine yeast strains using (1)H nuclear magnetic resonance (NMR) spectroscopy coupled with multivariate statistics. Principal component analysis (PCA) showed clear differentiation between non- and induced-malolactic fermented wines by wine lactic acid bacteria (LAB) and between wines fermented with various wine yeast strains. Metabolites such as glycerol, lactate, 2,3-butanediol, succinate, leucine, isoleucine, alanine, valine, proline, choline, gamma-aminobutyric acid (GABA), and polyphenols contributed to the differentiations. Decreased levels of malate and citrate along with increased levels of lactate were the metabolites most responsible for the differentiation of induced-MLF wines from non-MLF wines. In particular, high succinate levels provided evidence of an inhibitory effect of Saccharomyces bayanus against spontaneous MLF. Furthermore, dependence of metabolites on wine yeast strains was observed, demonstrating their different fermentative behaviors. This study demonstrates that wine fermentation by yeast and LAB can be characterized through global and multivariate statistical analysis of (1)H NMR spectral data.

Quality Characteristics of Takju Produced by Adding Different Amounts of Water

The effect of the amount of water added during fermentation on the quality of takju (rice beer) was investigated. Takju was made by adding water 2-fold (A), 4-fold (B), 5-fold (C), and 6-fold (D), respectively, of the rice weight (w/w). Although the amount of takju increased in proportion to the amount of water added before fermentation, the amounts of B, C, and D were 1.17-1.19 times larger than the amount in A, and the total acidities of B, C, and D were 1.34, 1.40 and 1.46 times higher than those in A after adjusting alcohol content to 6%(v/v). Moreover, the sensory preferences for B, C, and D were higher overall than those for A, which was suggested to be due to the amount of sweet, sour, and bitter tastes as well as body in A. Different types of takju could be made by changing the amount of water added before fermentation.

Biotransformation of major ginsenosides in ginsenoside model culture by lactic acid bacteria

Background Some differences have been reported in the biotransformation of ginsenosides, probably due to the types of materials used such as ginseng, enzymes, and microorganisms. Moreover, most microorganisms used for transforming ginsenosides do not meet food-grade standards. We investigated the statistical conversion rate of major ginsenosides in ginsenosides model culture during fermentation by lactic acid bacteria (LAB) to estimate possible pathways. Methods Ginsenosides standard mix was used as a model culture to facilitate clear identification of the metabolic changes. Changes in eight ginsenosides (Rb1, Rb2, Rc, Rd, Re, Rf, Rg1, and Rg2) during fermentation with six strains of LAB were investigated. Results In most cases, the residual ginsenoside level decreased by 5.9–36.8% compared with the initial ginsenoside level. Ginsenosides Rb1, Rb2, Rc, and Re continuously decreased during fermentation. By contrast, Rd was maintained or slightly increased after 1 d of fermentation. Rg1 and Rg2 reached their lowest values after 1–2 d of fermentation, and then began to increase gradually. The conversion of Rd, Rg1, and Rg2 into smaller deglycosylated forms was more rapid than that of Rd from Rb1, Rb2, and Rc, as well as that of Rg1 and Rg2 from Re during the first 2 d of fermentation with LAB. Conclusion Ginsenosides Rb1, Rb2, Rc, and Re continuously decreased, whereas ginsenosides Rd, Rg1, and Rg2 increased after 1–2 d of fermentation. This study may provide new insights into the metabolism of ginsenosides and can clarify the metabolic changes in ginsenosides biotransformed by LAB.

Quality Characteristics of Korean Black Raspberry Bokbunja Wines Produced Using Different Amounts of Water in the Fermentation Process

School of Life Science and Biotechnology, Korea UniversityAbstract In this study, we investigated the effect of the amount of water added prior to fermentation on the quality ofbokbunja (Rubus coreanus Miq.) wine produced. Water was added at 0-fold (A), 1-fold (B), 2-fold (C), 3-fold (D), and4-fold (E) of the fresh bokbunja weight (w/w), prior to fermentation. Although the amount of bokbunja wine obtained afterfermentation increased in proportion to the amount of water added prior to fermentation, the total acidity of the bokbunjawine, adjusted for the weight of bokbunja used in the fermentation process, increased. Moreover, the total phenol andflavonoid content (mg) per weight (g) of bokbunja, in (B), (C), (D), and (E) were 2.86-4.42 and 2.58-3.01 times higher,respectively, than those in (A). These data suggest that different types of bokbunja wines can be produced and differentcontents of total phenol can be obtained by simply changing the amount of water added prior to fermentation.Keywords: bokbunja, wine, water, total phenol, total flavonoid

Metabolic phenotyping of berries in different six grape (Vitis vinifera) cultivars

Metabolic behaviors of different grapevine cultivars, grown in the same greenhouse, were characterized through a 1H NMR-based metabolomic approach. Pattern recognition, including the principal component analysis, revealed clear dependence of the grape metabolome on the grape cultivar. Interestingly, high accumulations of proline in the purebred grape cultivars of Cabernet Sauvignon, Merlot, and Chardonnay were found, whereas the proline levels were depleted in the crossbred grape cultivars of Steuben, Campbell Early (C. E.), and Seibel. Intrinsic levels of alanine, glutamine, and trans-feruloyl derivative were highest in C. E. cultivar, which grows easily in a wild vineyard, particularly in Korea, suggesting that their levels play important roles in the improvement of resistance or adaptation of the plant to environmental stress, such as freezing stress during the winter season in Korea. The present study highlights that metabolomics is a powerful approach for better understanding the differences of intrinsic metabolic variables of grape berries among various grape cultivars and their associations with the plant physiological mechanisms.

Optimal Extraction Conditions to Produce Rosemary Extracts with Higher Phenolic Content and Antioxidant Activity

We evaluated the effects of temperature, time, solvent type, and solvent concentration on the phenolic content and antioxidant activity of rosemary extracts. The antioxidant capacity of rosemary extracts was demonstrated by their ability to scavenge stable free radicals, and the phenolic content of the extracts was determined using the Folin Ciocalteu method. The highest values were obtained by water-based extraction at 90 o C for 30 min, a 75% methanol solution at 60 o C for 30 min, and a 50% ethanol solution at 70 o C for 10 min. The aqueous solution of 75% methanol, extraction temperature of 60 o C, and extraction time of 30 min were the most efficient parameters for the extraction of polyphenols from dry rosemary.

Physicochemical Properties of Different Grape Varieties Cultivated in Korea

The aim of this study was to describe the effects of genetic factors on the chemical composition or metabolites of grapes harvested within the same region. Grapes were separated into pulp, skin, and seed, and physicochemical characteristics were compared among seven grape varieties. The sugar concentrations of the grape musts ranged from 15.17-20.93°Bx with Seibel variety being highest at 20.93°Bx. pH ranges of grape musts were 3.46-4.02 and total acidity was highest with 1.05 in Steuben variety. Tartaric acid content was highest with 146.68, 500.10 ㎎/L in pulp and skin extract of Merlot variety. Malic acid content was highest in pulp extract of Seibel variety (1127.14 ㎎/L) and skin extract of Chardonnay variety (1720.06 ㎎/L). K content was highest with 379.13 and 828.01 ㎎/L in pulp and skin extract of Chardonnay variety. Ca content was highest in pulp extract of Kyoho variety (6.98 ㎎/L) and skin extract of Campbell Early variety (12.26 ㎎/L).