Inmyoung Park

Determination of organic milk authenticity using carbon and nitrogen natural isotopes

Natural stable isotopes of carbon and nitrogen ((12)C, (13)C, (14)N, (15)N) have abundances unique to each living creature. Therefore, measurement of the stable isotope ratio of carbon and nitrogen (δ(13)C=(13)C/(12)C, δ(15)N=(15)N/(14)N) in milk provides a reliable method to determine organic milk (OM) authenticity. In the present study, the mean δ(13)C value of OM was higher than that of conventional milk (CM), whereas the mean δ(15)N value of OM was lower than that of CM; nonetheless both δ(13)C and δ(15)N values were statistically different for the OM and CM (P<0.05). Furthermore, the values of δ(13)C and δ(15)N were found to differ statistically with the collection date and the milk brand (P<0.05). The combination of δ(13)C and δ(15)N values was more effective than either value alone in distinguishing between OM and CM. The results of the present study, which is based on preliminary data from a limited sample size and sampling period, could be highly valuable and helpful for consumers, the food industry, and/or government regulatory agencies as it can prevent fraudulent labelling of organic food. Further studies include additional analyses of other milk brands and analyses over longer time periods in order to accurately determine OM authenticity using stable isotopes of carbon and nitrogen.

Variation and correlation analysis of phenolic compounds in mungbean (Vigna radiata L.) varieties

Phenolic compounds from a wide collection of mungbean [Vigna radiata (L.) Wilczek] germplasm (56 varieties) were characterised to determine the diversity among these phytochemicals and to analyse the relationships among their contents. The profiles of 25 phenolic compounds identified from the grains were subjected to data-mining processes, including principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), Pearsons correlation analysis, and hierarchical clustering analysis (HCA). The IT212105 and IT104818 varieties separated from the others in the first two principal components of PCA. PLS-DA showed significant separation between extracts of mungbean originating from three countries: China, Japan, and Korea. HCA of these phytochemicals resulted in clusters derived from common or closely related biochemical pathways. Significant positive relationships were observed between coumaric acid and resveratrol (r=0.7195, p<0.0001). Catechin content was positively correlated with rutin (r=0.6291, p<0.0001). The IT104818 variety appears to be a good candidate for future breeding programs, as it contains high levels of phenolic compounds. These results demonstrate the use of metabolic profiling combined with chemometrics as a tool for assessing the quality of food.

Isoflavones profiling of soybean [Glycine max (L.) Merrill] germplasms and their correlations with metabolic pathways

The isoflavone diversity (44 varieties) of the soybean, Glycine max (L.) Merrill, from China, Japan, and Korea was examined by high-performance liquid chromatography. The profiles of 12 isoflavones identified from the grains were subjected to data-mining processes, including partial least-squares discriminant analysis (PLS-DA), Pearsons correlation analysis, and hierarchical clustering analysis (HCA). Although PLS-DA did not reveal significant differences among extracts of soybean from 3 countries, the results clearly show that the variation between varieties was low. The CS02554 variety was separate from the others in the first 2 principal components of PLS-DA. HCA of these phytochemicals resulted in clusters derived from closely related biochemical pathways. Daidzin, genistin, and glycitin contents were significantly correlated with their respective malonyl glycoside contents. Daidzein content correlated positively with genistein content (r=0.8189, P<0.0001). The CS02554 variety appears to be a good candidate for future breeding programs, as it contains high levels of isoflavone compounds. These results demonstrate the use of metabolite profiling combined with chemometrics as a tool for assessing the quality of food and identifying metabolic links in biological systems.

Isoflavone Content and Profile Comparisons of Cooked Soybean–Rice Mixtures: Electric Rice Cooker versus Electric Pressure Rice Cooker

This study examined the effects of heat and pressure on the isoflavone content and profiles of soybeans and rice cooked together using an electric rice cooker (ERC) and an electric pressure rice cooker (EPRC). The total isoflavone content of the soybean-rice mixture after ERC and EPRC cooking relative to that before cooking was ∼90% in soybeans and 14-15% in rice. Malonylglucosides decreased by an additional ∼20% in EPRC-cooked soybeans compared to those cooked using the ERC, whereas glucosides increased by an additional ∼15% in EPRC-cooked soybeans compared to those in ERC-cooked soybeans. In particular, malonylgenistin was highly susceptible to isoflavone conversion during soybean-rice cooking. Total genistein and total glycitein contents decreased in soybeans after ERC and EPRC cooking, whereas total daidzein content increased in EPRC-cooked soybeans (p < 0.05). These results may be useful for improving the content of nutraceuticals, such as isoflavones, in soybeans.

Effects of milk type, production month, and brand on fatty acid composition: A case study in Korea.

The aim of this study was to examine the difference in fatty acid (FA) composition of organic and conventional milk at the retail market level in Korea for different milk production months and brands. The essential FA contents of the milk vary significantly under the combined effects of milk type, production month, and brand. Chemometric analysis reveals a greater difference between milk types than between production months and identifies significantly different levels of nutritionally desirable FAs-notably C18:3 n-3, C18:2 n-6 c and t-in the organic and conventional milks. Notwithstanding the limited sampling size and period, the results from this study may provide a better understanding of the nutritional quality of organic milk to consumers who are interested in organic milk intake.

Differential regulation of toxoflavin production and its role in the enhanced virulence of Burkholderia gladioli

Burkholderia gladioli is a causal agent of bacterial panicle blight and sheath/grain browning in rice in many countries. Many strains produce the yellow pigment toxoflavin, which is highly toxic to plants, fungi, animals and microorganisms. Although there have been several studies on the toxoflavin biosynthesis system of B. glumae, it is still unclear how B. gladioli activates toxoflavin biosynthesis. In this study, we explored the genomic organization of the toxoflavin system of B. gladioli and its biological functions using comparative genomic analysis between toxoflavin-producing strains (B. glumae BGR1 and B. gladioli BSR3) and a strain not producing toxoflavin (B. gladioli KACC11889). The latter exhibits normal physiological characteristics similar to other B. gladioli strains. Burkholderia gladioli KACC11889 possesses all the genes involved in toxoflavin biosynthesis, but lacks the quorum-sensing (QS) system that functions as an on/off switch for toxoflavin biosynthesis. These data suggest that B. gladioli has evolved to use the QS signalling cascade of toxoflavin production (TofI/TofR of QS → ToxJ or ToxR → tox operons) similar to that in B. glumae. However, some strains may have evolved to eliminate toxoflavin production through deletion of the QS genes. In addition, we demonstrate that the toxoflavin biosynthetic system enhances the virulence of B. gladioli. These findings provide another line of evidence supporting the differential regulation of the toxoflavin system in Burkholderia strains.

Understanding the direction of evolution in Burkholderia glumae through comparative genomics

Members of the genus Burkholderia occupy remarkably diverse niches, with genome sizes ranging from ~3.75 to 11.29 Mbp. The genome of Burkholderia glumae ranges in size from ~5.81 to 7.89 Mbp. Unlike other plant pathogenic bacteria, B. glumae can infect a wide range of monocot and dicot plants. Comparative genome analysis of B. glumae strains can provide insight into genome variation as well as differential features of whole metabolism or pathways between multiple strains of B. glumae infecting the same host. Comparative analysis of complete genomes among B. glumae BGR1, B. glumae LMG 2196, and B. glumae PG1 revealed the largest departmentalization of genes onto separate replicons in B. glumae BGR1 and considerable downsizing of the genome in B. glumae LMG 2196. In addition, the presence of large-scale evolutionary events such as rearrangement and inversion and the development of highly specialized systems were found to be related to virulence-associated features in the three B. glumae strains. This connection may explain why this bacterium broadens its host range and reinforces its interaction with hosts.

Effects of air, microwave, and microvacuum drying on brown rice quality

Proper hulling and drying are critical components of brown rice quality. Two medium grain rice varieties were examined for grain qualities including husking, cracking, germination ratio, color, hardness, and fat acidity after drying with 15, 30, and 45°C air, as well as at 100 and 200 W microwave, and microwavevacuum, respectively. Unlike impeller dehuller, rubber roller dehuller could not process rice with 22% moisture content. Brown rice varieties with 22% moisture content after dehulling were dried at 15, 30, and 45°C until moisture content reached 15%; the drying ratios for each temperature were 1.02, 2.55, and 3.46 %/h, respectively. When brown rice varieties were dried at below 30°C, no significant changes were observed in physico-chemical properties, whereas the cracking ratio increased significantly. Microwavevacuum drying resulted in higher reductions of germination ratio and fat acidity than with the microwave only at 100 W as well as reduced drying time over microwave drying.

Computational Identification and Comparative Analysis of Secreted and Transmembrane Proteins in Six Burkholderia Species

As a step towards discovering novel pathogenesis-related proteins, we performed a genome scale computational identification and characterization of secreted and transmembrane (TM) proteins, which are mainly responsible for bacteria-host interactions and interactions with other bacteria, in the genomes of six representative Burkholderia species. The species comprised plant pathogens (B. glumae BGR1, B. gladioli BSR3), human pathogens (B. pseudomallei K96243, B. cepacia LO6), and plant-growth promoting endophytes (Burkholderia sp. KJ006, B. phytofirmans PsJN). The proportions of putative classically secreted proteins (CSPs) and TM proteins among the species were relatively high, up to approximately 20%. Lower proportions of putative type 3 non-classically secreted proteins (T3NCSPs) (~10%) and unclassified non-classically secreted proteins (NCSPs) (~5%) were observed. The numbers of TM proteins among the three clusters (plant pathogens, human pathogens, and endophytes) were different, while the distribution of these proteins according to the number of TM domains was conserved in which TM proteins possessing 1, 2, 4, or 12 TM domains were the dominant groups in all species. In addition, we observed conservation in the protein size distribution of the secreted protein groups among the species. There were species-specific differences in the functional characteristics of these proteins in the various groups of CSPs, T3NCSPs, and unclassified NCSPs. Furthermore, we assigned the complete sets of the conserved and unique NCSP candidates of the collected Burkholderia species using sequence similarity searching. This study could provide new insights into the relationship among plant-pathogenic, human-pathogenic, and endophytic bacteria.

Development and comparison of analytical methods for measuring simazine herbicide using gas chromatography/ion trap, gas chromatography/mass selective detector, and high performance liquid chromatography/triple quadrupole mass spectrometers

Simazine is widely used to manage weed growth in the agricultural and industrial fields. Three analytical methods, including gas chromatography (GC)/ion-trap (IT), GC/mass selective detector (MSD), and high-performance liquid chromatography (HPLC)/triple quadrupole mass spectrometers (HPLC/MS/MS), were developed and compared for simazine quantification. The spike recoveries by GC/IT, GC/MSD, and HPLC/MS/MS were 100, 117, and 82.5%, respectively. Different spike recovery depending on analytical methods could be due to matrix effect, different instrumental sensitivity, losses during sample preparation or all of the above. The limit of detection was 0.0361, 0.0263, and 0.0013 mg/kg by GC/IT, GC/MSD, and HPLC/MS/MS, respectively. The HPLC/MS/MS with a positive atmospheric pressure chemical ionization (APCI) ionization mode was the most rapid (7 min), sensitive (limit of detection: 0.0013 mg/kg, limit of quantification: 0.0042 mg/kg), and precise (relative standard deviation: 0.5%) method for simazine quantification.