Influence of Ulmi (Ulmus macrocarpa Hance) Cortex on Quality Characteristics and Antioxidant activity of Korean Traditional Wine, Takju

Ulmi (Ulmus macrocarpa Hance) is an oriental medicinal plant that shows huge potential against several metabolic disorders. The purpose of this study was to investigate the effect of addition of ulmi root cortex extracts on the quality characteristics and antioxidant activity of Korean traditional wine (takju). Four takju samples containing different proportions of the extracts were prepared; namely UCT-0: takju prepared by adding 0% ulmi cortex extracts, UCT-1: takju prepared by adding 1% ulmi cortex extracts, UCT-5: takju prepared by adding 5% ulmi cortex extracts, and UCT-10: takju prepared by adding 10% ulmi cortex extracts. Alcohol contents (6.01‒ 6.11%) and pH levels (4.01‒4.11) of all four types of takju were not significantly different. The titratable acidity value was the lowest in UCT-0 (0.19 g/100 ml) among the four samples. The soluble solid content was the highest in UCT-10 (4.1 °Brix). The lightness (L*) values were in the order of UCT-0 (55.66) > UCT-1 (50.22) > UCT-5 (47.12) > UCT-10 (40.00). The more the amount of ulmi cortex extracts added, the more the redness (a*) values of the takju observed. The higher scores for overall taste were found for UCT-5 sample as compared to the other samples. The range of the DPPH (1,1-Diphenyl-2-picryl-hydrazyl) free radical scavenging potential in all samples ranged from 39.83% (UCT-0) to 45.91% (UCT-5). Total polyphenol content was in order of UCT-5 (373.44 μg/ml) > UCT-5 (362.11 μg/ml) > UCT-1 (340.44 μg/ml) > UCT-0 (344.22 μg/ml). The results indicated that addition of 5% root cortex extract of ulmi could be used to produce antioxidant-rich takju with highest overall acceptance.


Introduction
Ulmi (Ulmus macrocarpa Hance) is a deciduous medicinal plant that is widely distributed in Korea. The stem and root cortexes of this plant have been used as oriental traditional medicine for the treatment of various health disorders, such as edema, gastric cancer, and inflammation (Kwon et al., 2011;Oh et al., 2008;Park et al., 2020;Han et al., 2019). The cortexes contain several phytochemicals, including flavonoids, saponins, tannins, phlegmatic, β-sitosterol, phytosterol, sigmasterol, and resin. Ulmi cortex extracts are effective as anti-inflammatory, anthelmintic, and antibacterial activity. Takju, more commonly known as makgeolli, a famous Korean traditional alcoholic beverage, is produced by brewing yeast (Saccharomyces cerevisiae); cereals, mostly glutinous rice; nuruk, a fermentation starter, containing yeast and several types of fungi. It is rich in protein and carbohydrates and also contains a small amount of organic compounds. Traditional alcoholic beverages are widely consumed in Korea. It contains about 6% alcohol with a characteristic fragrance and a sweet taste.
Several studies have been carried out to improve the quality of Korean traditional rice wines and liquors (Takizawa, 1999. Different additives such as chamomile , acasia (Seo et al., 2002), Paecilomyces japonica  have already been used to produce varieties of Korean traditional rice wines of improved quality. The physicochemical characteristics and antioxidant potential of traditional wine has gradually improved with the addition of different additives, resulting in increased sales in recent years; however, problems still exist.
A number of active substances, including polyphenols, polysaccharides, and polysaccharidepeptide complexes are detected in takju (Lee et al., 1996;Park and Lee, 2002). These active substances found in takju show various chemical characteristics and biological effects, such as antioxidant and immunomodulating activities. Few takju samples also contain substantial amount of total polyphenol contents compared to white wine. The objective of this study was to investigate the physicochemical characteristics and antioxidant activity of takju prepared by the addition of different proportions of ulmi cortex extracts.

Materals and methods Materials
Ulmi cortex powder, rice, yeast (Saccharomyces cerevisiae), and nuruk were purchased from a local market in Daegu, Korea.

Preparation of ulmi cortex extracts
Entire roots (15 g) of ulmi cortex were thoroughly washed with tap water and were cut into small pieces, and then boiled with 3 L water for 30 min in a stainless steel container. The extraction solution was allowed to cool and filtered through Whatman No. 2 filter paper. The samples were stored at 4°C.

Takju sample preparation
A typical Korean traditional wine, takju is prepared by 2-step fermentation of steamed rice. Nuruk is added only in the second step but not in the first step of fermentation. However, in this experiment, we studied the effect of the addition of nuruk in the first step of fermentation as well. The ulmi cortex extracts were added in the second step of fermentation. Briefly, in the first step, the mixture of rice koji, commercially available steamed rice (2 kg), yeast (2.5 g), and water (3 L) was fermented at 25°C for 1 d. In the second step, the mixture of steamed rice (8 kg), nuruk (200 g), water (12 L), and different proportions of ulmi cortex extracts were mixed and fermented at 25°C for 6 d. Four different samples were prepared and named as UCT-0: Ulmi cortex takju prepared with adding of 0 % ulmi cortex extracts, UCT-1: Ulmi cortex takju prepared with adding of 1% ulmi cortex extracts, UCT-5: Ulmi cortex takju prepared with adding of 5% ulmi cortex extracts, UCT-10: Ulmi cortex takju prepared with adding of 10% ulmi cortex extracts

Chemical parameters
Chemical parameters, such as pH, titratable acidity (TA), alcohol, and soluble solid content (SSC) were considered for the evaluation of different takju samples. The pH was measured with a pH meter (Beckman 250, Beckman Coulter Inc., Fullerton, CA, USA). The TA (g/100 ml lactic acid) was measured by adding 5 mL of takju samples to 125 mL of deionized water and titrating with 0.1 N sodium hydroxide to an endpoint pH of 8.2. The alcohol level was analyzed by following a method described earlier (Ough and Amerine, 1988), and the SSC (°Brix) was measured according to the Official Methods of National Tax Service, Korea (NRRDI, 2006). All the measurements were replicated three times and the average values were reported.

Determination of DPPH radical scavenging activity
The DPPH'(1,1-diphenyl-2-picrylhydrazol) radical scavenging activity of ulmi cortex takju was measured by following the method described earlier (Blois, 1958;Shyu and Hwang, 2002). Briefly, 0.5 mM solution of DPPH' in methanol and 0.05 M acetate buffer (pH 5.5) was prepared. An aliquot of 0.1 mL (at concentrations 0.5−0.1 mg/mL) of the takju sample was added to 2 mL acetate buffer, 1.9 mL methanol and 1 mL DPPH' solution. Blanks contained 2 mL acetate buffer, 1.9 mL methanol and 0.1 mL ulmi cortex takju, while the control contained 2 mL acetate buffer, 1 mL DPPH' and 2 mL methanol. The mixture was shaken immediately after adding DPPH' and allowed to stand at room temperature in the dark, and the decrease in absorbance at 517 nm using a spectrophotometer (Shimadzu UV-1700UV, Shimadzu Corporation, Kyoto, Japan) was measured after 30 min until they reached a plateau. The inhibitory percentage of the DPPH' radical by the samples was calculated as follows: where A, A b, and A o are the absorbance values of the sample extracts with DPPH, control, and blank, respectively.

Determination of total phenol content
The total phenol content of ulmi cortex takju samples were determined by following the Folin-Ciocalteu method as described by George et al. (2005) with some modification. In brief, 0.79 ml of distilled water 0.01 ml of diluted sample, and 0.05 ml of phenol reagent were added to a 1.5 ml Eppendorf tube, then mixed. After 1 min, 0.15 ml of 20% sodium carbonate was added, and the mixture was mixed and allowed to stand at room temperature for 120 min. The absorbance was then read at 750 nm and the total polyphenol content was calculated from calibration curve, using gallic acid as a standard.

Sensory analyses
Sensory analyses were performed on freshly made ulmi cortex takju. Samples made with different conditions were rated for overall taste on the following scales: 1 point= very poor, 2 point= poor, 3 point= fair, 4 point= good, 5 point= very good. The results showed average value of each evaluation. All tests were conducted by 15 evaluators randomly selected from our department.

Statistical analysis
Analysis of variance was conducted using SAS 9.4 (SAS Institute, Cary, NC, USA) and the significance differences between sample means were determined using the Tukey test at 5% probability. Average values of three replications are reported unless otherwise mentioned.
2) As lactic acid. 3) Quoted values are means±SD of triplicate measurements. Values followed by different letters in the same row are significantly different (p<0.05).

Color and overall taste of ulmi takjus
Color values and overall taste of four ulmi cortex takjus prepared by the addition of different ulmi cortex extracts were presented in Table 2. The L* value is a measure of lightness (100, white; 0, black), from completely opaque (0) to completely transparent (100); a* is a measure of redness (-, blue; +, yellow) and b* is a measure of yellowness (-, blue The more the amount of ulmi cortex extracts added the more the redness (a*) values of the takju increased. Sensory characteristics was determined by overall taste. It was found that higher scores for overall taste were found for UCT-5 sample as compared to the other sample. Scavenging activities and total phenolic contents of ulmi cortex takjus DPPH' radical scavenging ability and total phenolic content in ulmi cortex takjus were determined. The results were presented in Table 3

Conclusions
The addition of ulmi cortex extracts to takju enhanced the overall taste and antioxidant potentials. Takjus prepared by adding different concentrations of ulmi cortex extracts could be used as good sources of taste and antioxidants in the human health. Optimum conditions for the addition of ulmi cortex extracts of ulmi cortex takjus were evaluated with adding of 5% ulmi cortex extracts (UCT-5 sample). Results of this study suggested that addition of ulmi cortex extracts to takju could impart better physicochemical properties as well as enhance the antioxidant potentials.