Yonghoon Lee

This study demonstrates that laser-induced breakdown spectroscopy, combined with systematic variable selection and machine learning, enables efficient discrimination between domestically produced and imported red chili powders in Korea.

Background/Objectives: Kimchi has gained global recognition for its unique taste and health benefits, but its quality is totally different according to its geographical origin of materials and production methods. Methods: In this study, differences between Korean (53 samples) and Chinese kimchi (72 samples) were investigated through comprehensive metabolomic analysis using gas chromatography–mass spectrometry (GC-MS) and ultra-performance liquid chromatography–quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF MS). Results: Multivariate statistical analyses revealed a clear separation between the two groups. Thirty-four metabolites contributing to the separation were identified. Korean kimchi was enriched in sucrose, quinic acid, sinapic acid derivatives, rutin, capsicosin, and capsianoside, while Chinese kimchi contained higher levels of trihydroxy octadecenoic acid, 2-hydroxypalmitic acid, pinellic acid, maltose, glucuronic acid, and corchorifatty acid F. In particular, the univariate Bayesianlogistic regression analysis revealed that among these metabolites, rutin, capsicosin derivatives, and sinapic acid derivatives showed strong potential as origin-discriminant markers of kimchi, providing insights into how these metabolites influence its nutritional and sensory properties. Conclusions: These compositional differences may be attributed to variations in raw materials and production methods of kimchi.

This study combines LIBS and IR spectroscopy to classify kimchi by country of origin, achieving 96.8% accuracy using a fused k-NN model.

Spodumene (LiAlSi₂O₆) is a key lithium source mineral for energy storage devices, making the accurate and rapid analysis of its elemental composition crucial for the battery industry. This study explores the use of laser-induced breakdown spectroscopy (LIBS) combined with the standard addition method to analyze Be, Na, and K in spodumene. The method achieved relative errors of 5%–15% compared to inductively coupled plasma optical emission spectroscopy (ICP-OES), without requiring certified standards. To ensure accuracy, non-resonance emissions were used for Be and Na to minimize self-absorption effects. Although K analysis faced challenges due to strong self-absorption in resonance emissions, focusing on weak edge intensity reduced the relative error significantly. Our results suggest that LIBS combined with the standard addition method is a promising approach for lithium ore analysis, eliminating the need for certified standard materials and complex sample preparation steps such as acid digestion and high-factor dilution.

Multiple coffee bean products were classified using laser-induced breakdown spectroscopy and k -nearest neighbors modeling with 98.5% accuracy. A novel metric, termed inter-to-intraclass variation ratio, identified Li, Na, and Rb as key variables.

This study explores the use of a cost‐effective laser‐induced breakdown spectroscopy (LIBS) instrument for analyzing magnesium (Mg) in fermented soybean pastes. Composed of soybeans and salts, these pastes are rich in proteins and minerals. A low‐power diode‐pumped solid‐state laser and a miniature low‐resolution spectrometer were used to analyze nine products, with Mg concentrations previously determined via inductively‐coupled plasma optical emission spectroscopy. The LIBS spectra showed Mg II and Mg I emission peaks at 279.8 and 285.2 nm, respectively, used to create univariate calibration models. Additionally, a partial‐least‐squares regression (PLS‐R) model showed superior accuracy. Mg concentrations correlated with the types of salts used. The study demonstrates the feasibility of using real products as calibration standards for LIBS, supported by other methods. The compact, low‐cost LIBS instrument offers an alternative for quantitative mineral analysis and raw material identification in fermented soybean pastes.

Salt, one of the most commonly consumed food additives worldwide, is produced in many countries. The chemical composition of edible salts is essential information for quality assessment and origin distinction. In this work, a simple laser-induced breakdown spectroscopy instrument was assembled with a diode-pumped solid-state laser and a miniature spectrometer. Its performances in analyzing Mg and Ca in six popular edible sea salts consumed in South Korea and classification of the products were investigated. Each salt was dissolved in water and a tiny amount of the solution was dropped and dried on the hydrophilicity-enhanced silicon wafer substrate, providing homogeneous distribution of salt crystals. Strong Mg II and Ca II emissions were chosen for both quantification and classification. Calibration curves could be constructed with limits-of-detection of 87 mg/kg for Mg and 45 mg/kg for Ca. Also, the Mg II and Ca II emission peak intensities were used in a k-nearest neighbors model providing 98.6% classification accuracy. In both quantification and classification, intensity normalization using a Na I emission line as a reference signal was effective. A concept of interclass distance was introduced, and the increase in the classification accuracy due to the intensity normalization was rationalized based on it. Our methodology will be useful for analyzing major mineral nutrients in various food materials in liquid phase or soluble in water, including salts.

In this work, we applied a hydrophilicity-enhanced solid substrate and an alternating laser-ablation data sampling (ALADS) scheme to improve laser-induced breakdown spectroscopy (LIBS) measurement precision and demonstrated the performance in analyzing K, Mg, Ca, and S contained in commercially available edible salt products. Five edible salt products from Australia, Bolivia, France, and South Korea were dissolved in water and a tiny volume of each solution was dropped on the solid substrate, that is, a miniaturized salt pond. After being dried, the residual salt crystals distributed still inhomogeneously, but the homogeneity could be significantly improved in comparison with that from typical drop-and-dry methods. The ALADS scheme was applied to extract three precise measurements from 9798 single-shot LIBS spectra covering the entire salt pond. The measurements obtained by ALADS were found to agree well with one another regardless of the inhomogeneous distribution of salt crystals. As a result, the measurement precision was proved remarkably. Limits of detection for K, Mg, Ca, and S were estimated to be 0.64, 1.7, 14, and 530 mg/kg, respectively, which are enough to analyze those elements contained in salts typically at the level of 100 parts per million (ppm) to ∼3 wt% for the purpose of salt quality assessment.