• Journal of Applied Biological Chemistry
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• v.57 no.4
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• pp.353-358
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• 2014

Antioxidant activities of ethanol and water extracts of flesh, leaves, and peels of green and purple Kohlrabi were measured by rancimat method, total phenolic compound (TPC), DPPH radical scavenging effect, chelating effect, and reducing power analysis. The highest TPC was observed in ethanol extract from green peel and water extract from purple leaf with 12.00 and 11.70 mg/g of dry sample, respectively. The ethanol extracts from purple Kohlrabi leaf and peel exhibited strong DPPH radical scavenging effects with reducing power while water extracts from purple Kohlrabi leaf and peel also showed strong DPPH radical scavenging with chelating effects. Antioxidant index of ethanol and water extracts from green and purple Kohlrabi measured by rancimat was lower than butylated hydroxytoluene. These results suggest that extracts from purple Kohlrabi leaf and peel exhibited higher antioxidant activities than those of green Kohlrabi, and can be potentially used as proper natural antioxidants.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.189-202
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• 2017

This study was designed to examine the in vitro antioxidant and anti-inflammatory effects of kohlrabi (Brassica oleracea var. gonglodes) extract. Kohlrabi was extracted using 70% ethanol and then fractionated sequentially with n-hexane, ethyl acetate and butanol. Antioxidative ability was evaluated by bioassays using total polyphenol contents and ABTS (2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid diammonium salt) radical scavenging activity. Ethyl acetate fraction of kohlrabi was best on total polyphenol contents ($27.33{\pm}0.26mg\;GAE/g$) and ABTS radical scavenging effects ($IC_{50}\;172.9{\pm}1.6{\mu}g/mL$).For the anti-inflammatory activity in RAW 264.7 cells, the EtOAc fraction showed the highest inflammatory effect. Dose response studies were performed to determine the inhibitory effect of EtOAc fraction of kohlrabi on pro-inflammatory mediators in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. The EtOAc fraction of kohlrabi inhibited the NO and $PGE_2$ production and the protein level of iNOS and COX-2, and protein expression of pro-inflammatory cytokines (TNF-${\alpha}$, IL-6 and IL-$1{\beta}$), in a dose-dependent manner. These results suggest that kohlrabi has considerable potential as a ingredient with antioxidative and anti-inflammatory effects.

• Korean Journal of Food Science and Technology
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• v.46 no.5
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• pp.601-608
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• 2014

In this study, we investigated the antioxidant activity of green kohlrabi juice (GKJ) and purple kohlrabi juice (PKJ) using various in vitro methods. The results of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activities, ferric ion reducing antioxidant power (FRAP), reducing power, and nitrite scavenging activities showed that GKJ possessed higher antioxidant activity than PKJ. Green kohlrabi powder (GKJP) and purple kohlrabi powder (PKJP) inhibited hydrogen peroxide-induced cell death in human dermal fibroblasts. In addition, GKJP and PKJP suppressed intracellular reactive oxygen species (ROS) production induced by hydrogen peroxide in human dermal fibroblasts. These results suggest that green and purple kohlrabi juices are potential natural sources of antioxidants.

• Journal of Bio-Environment Control
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• v.28 no.2
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• pp.104-109
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• 2019

The crops recommended for the plant factory system are diverse. The importance of planting density in the plant factory is being recognized. The objective of this study was to determine the optimal planting density for growth and quality of kohlrabi in a closed-type plant factory system. The kohlrabi was grown under fluorescent lamps and nutrient film technique system. The growth and quality of kohlrabi were investigated under four different planting densities ($22plants/m^2(15{\times}30cm)$, $27plants/m^2(15{\times}25cm)$, and $33plants/m^2(15{\times}20cm)$). There were no significant interactions between Shoot fresh and dry weights per plant or bulb stem fresh and dry weights per plant and planting density. Shoot fresh and dry weight per area or bulb stem fresh and dry weight per area were the highest at $33plants/m^2$. There were no significant interactions between plant height, leaf area, photosynthetic rate, hardness, and chlorophyll content and planting density. Significant differences in Bulb stem height and diameter, and brix were observed. Bulb stem height and diameter and brix of kohlrabi were the highest at $22plants/m^2$. Based on our results, we conclude that the optimal planting density is $33plants/m^2$ for growth of kohlrabi, however, the optimal planting density is $22plants/m^2$ for quality of kohlrabi in a closed-type plant factory system.

• Preventive Nutrition and Food Science
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• v.15 no.2
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• pp.152-158
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• 2010

This study was designed to determine the best cultivar of kohlrabi for making pickles among KM-1 (Worldcol), KM-2 (Bejo), KM-3 (Takii), and KM-4 (Monsanto) cultivars. The initial pH of pickles was different in all cultivars; however, they all had a pH in the range of 3.81~3.86 after 28 days of storage. The pickles made from KM-4 had the lowest acidity, while there was no significant difference in acidity among the KM-1, KM-2, and KM-3 pickles. The salinity of all kohlrabi pickles was consistent during the storage period. The changes of color values were accelerated in the following order: KM-4>KM-1>KM-2>KM-3. Though kohlrabi pickles were non-fermented, the change in reducing sugar contents was similar to that of a fermented pickle. The highest value of reducing sugar content was found in pickles made with KM-4. In all cases, the firmness of the pickle decreased as time of storage increased. On the initial day, KM-4 pickle showed the highest firmness with 807.4 g. KM-4 also showed the highest firmness on the 28th day of storage with 602.3 g. In sensory evaluation, the KM-4 pickle exhibited the highest texture (hardness) among the pickles. The pickle made with the KM-4 cultivar showed relatively higher firmness of texture than other cultivars, suggesting that KM-4 could be utilized in other kinds of processed foods, in addition to being pickled.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.12
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• pp.1994-2003
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• 2013

This study is performed to evaluate the effects of purple Kohlrabi addition on the quality properties and stability characteristics of hamburger patties during storage. The patties were prepared by adding 0% (N), 3.3% (K1), 6.6% (K2), and 10% (K3) of chopped purple Kohlrabi. Each patty was tested in triplicate and assigned to one of the four storage periods: 0, 5, 10, or 15 days. Addition of Kohlrabi decreased the protein and lipid contents, however, the ash and moisture contents were significantly increased. The total amino acid contents of N, K1, K2, and K3 were $15.34{\pm}1.02$, $14.57{\pm}1.28$, $15.10{\pm}1.17$, and $16.70{\pm}1.23$ mg/100 g, respectively. Palmitic acid was the most abundant among the saturated fatty acids, while oleic acid was the most abundant unsaturated fatty acids among the four groups. The water holding capacity value and cooking loss were not significantly different among the patties. In the textural characteristics, the addition of Kohlrabi increased the cohesiveness and chewiness values, but did not affect the hardness and springiness values of the patties. In the sensory evaluation, an addition of 10% Kohlrabi had the best score in color, flavor, and total acceptability. The pH of the patties decreased longer period storage; however, the total microbial counts, thiobarbituric acid (TBA) value and volatile basic nitrogen (VBN) content increased during storage. The TBA value and VBN content of the patties containing 10% Kohlrabi were lower than those of the N. Kohlrabi addition decreased the b (yellowness) and a (redness) values, and did not affect the L (lightness) value. Thus, this result suggests that adding Kohlrabi of 10% can be applied to patties for its functionality.

• Research in Plant Disease
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• v.25 no.1
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• pp.33-37
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• 2019

From 2016 to 2018, approximately 15% of kohlrabi were observed displaying significant clubroot symptoms in farmer's fields in Jeju, Korea. The initial infection appeared as hypertrophy of root hairs, and as the disease progressed, galls formation occurred on the main roots, finally disease progress resulted in yellowing and wilting of leaves. Pathogenicity was proven by artificial inoculation of plants with resting spore suspension, fulfilling Koch's postulates. The resting spore is one-celled, spherical and subspherical, colorless, and $3-5{\mu}m$ in diameter. On the basis of the morphological characteristics and phylogenetic analyses of internal transcribed spacer rDNA, the causal agent was identified as Plasmodiophora brassicae. To our knowledge, this is the first report on the occurrence of P. brassicae on kohlrabi in Korea.

• Bulletin of the Korean Chemical Society
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• v.28 no.2
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• pp.246-250
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• 2007

The crude extract of kohlrabi (Brassica oleracea gongylodes) was prepared as a rich source of peroxidase and its enzymatic and specific activities in the presence of cross-linked polyvinylpyrrolidone as a stabilizer were determined. This extract was used to catalyze the oxidation of thiamine in the presence of hydrogen peroxide to thiochrome at pH 8.0. Thiochrome shows strong fluorescence at 436 nm with excitation at 370 nm. Based on the obtained results, a sensitive and simple spectrofluorimetric method was developed for the determination of thiamine. In the optimum conditions, the calibration graph was linear from 2 × 10-7 to 1 × 10-4 mol L-1, with a detection limit of 6.2 × 10-8 mol L-1. The relative standard deviation (RSD) was 1.2% for 5 × 10-6 mol L-1 thiamine. The method was successfully applied to the determination of thiamine in vitamin B1 and vitamin B complex tablets and vitamin B complex syrup.

• Food Science and Preservation
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• v.24 no.6
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• pp.778-785
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• 2017

This study was conducted to develop a predictive model for the growth of Escherichia coli strain RC-4-D isolated from red kohlrabi sprout seeds. We collected E. coli kinetic growth data during red kohlrabi seed sprouting under isothermal conditions (10, 15, 20, 25, and $30^{\circ}C$). Baranyi model was used as a primary order model for growth data. The maximum growth rate (${\mu}max$) and lag-phase duration (LPD) for each temperature (except for $10^{\circ}C$ LPD) were determined. Three kinds of secondary models (suboptimal Ratkowsky square-root, Huang model, and Arrhenius-type model) were compared to elucidate the influence of temperature on E. coli growth rate. The model performance measures for three secondary models showed that the suboptimal Huang square-root model was more suitable in the accuracy (1.223) and the suboptimal Ratkowsky square-root model was less in the bias (0.999), respectively. Among three secondary order model used in this study, the suboptimal Ratkowsky square-root model showed best fit for the secondary model for describing the effect of temperature. This model can be utilized to predict E. coli behavior in red kohlrabi sprout production and to conduct microbial risk assessments.

• Natural Product Sciences
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• v.26 no.3
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• pp.214-220
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• 2020

Brassica oleracea var. gongylodes (red kohlrabi) is a biennial herbaceous vegetable whose edible bulbotuber-like stem and leaves are consumed globally. Sliced red kohlrabi tubers were extracted using methanol and the concentrated extract was partitioned successively with dichloromethane (CH₂Cl₂), ethyl acetate (EtOAc), n-butanol (n-BuOH) and water (H₂O). Repeated column chromatography of EtOAc fraction through silica, sephadex LH-20 and RP-18 gel led to isolation of eleven compounds of which compound 1 was a new glycosylated indole alkaloid derivative, 1-methoxyindole 3-carboxylic acid 6-O-β-D-glucopyranoside. Others were known compounds namely, β-sitosterol glucoside (4), 5-hydroxymethyl-2-furaldehyde (5), methyl-1-thio-β-D-glucopyranosyl disulfide (6), 5-hydroxy-2-pyridinemethanol (7), (3S,4R)-2-deoxyribonolactone (8), n-butyl-β-D-fructopyranoside (9), uridine (10) and three fructose derivatives, D-tagatose (11), β-D-fructofuranose (12) and β-D-fructopyranose (13). Similarly, isolation from CH₂Cl₂ fraction gave two known indole alkaloids, indole 3-acetonitrile (2) and N-methoxyindole 3-acetonitrile (3). The structure elucidation and identification of these compounds were conducted with the help of ¹³C and ¹H NMR, HMBC, HMQC, EIMS, HR-ESIMS and IR spectroscopic data, and TLC plate spots visualization. Compounds 2, 3, 4, 5, 6, 7, 8 and 9 are noted to occur in kohlrabi for the first time. Different bioactivities of these isolated compounds have been reported in literature.