Characterization of Kimchi Flavor with Preconcentration by Head Space Solid-Phase Microextraction and Stir Bar Sorptive Extraction and Analysis by Gas Chromatography-Mass Spectrometry

Changes in volatile flavor compounds of Kimchi cabbage (Brassica rapa subsp. pekinensis) during salting and fermentation

A main ingredient of Kimchi is Kimchi cabbage, which is soaked in brine to reduce its crispness. Volatile profile of raw Kimchi cabbage (RC) is changed during salting; however, characteristic aroma-active compounds of salted Kimchi cabbage (SC) have not been investigated. The objective of this study was to evaluate changes in aroma characteristics of Kimchi cabbage during salting and fermentation. Sulfur-containing compounds, such as sulfides and isothiocyanates, increased markedly by salting. (Z)-3-Hexen-1-ol, (Z)-3-hexenal, and hexanal decreased by salting. Hexanal was the most intense in RC, followed by 3-(methylthio)butanal, (Z)-3-hexen-1-ol, and benzenepropanenitrile. Dimethyl trisulfide had the highest log3FD in SC. Methyl (methylthio)methyl disulfide, allyl methyl trisulfide, and dimethyl tetrasulfide were detected only in SC. Dimethyl trisulfide, dimethyl tetrasulfide, methyl (methylthio) methyl disulfide, and allyl methyl trisulfide, decreased greatly in SC during fermentation. Our results demonstrated that characteristic odor of Kimchi cabbage could be significantly changed by salting and fermentation.

Organosulfur in food samples: Recent updates on sampling, pretreatment and determination technologies

Organosulfur compounds (OSCs), mainly found in garlic, are the main biologically active substances for their pharmacological effects, including lowering of blood pressure and cholesterol, anti-cancer effect, liver protection, and anti-inflammatory. Efficient and sensitive pretreatment and determination methods of OSCs in different food matrices are of great significance. This review provides a comprehensive summary about the pretreatment and determination methods for OSCs in different food samples since 2010. Commonly used pretreatment methods, such as liquid-liquid extraction, microwave-assisted extraction, pressurized liquid extraction, liquid-liquid microextraction, solid phase extraction, dispersive solid phase extraction, solid-phase microextraction, and so on, have been summarized and overviewed in this paper. In particular, we discussed and compared various analysis methods including high performance liquid chromatography coupled with different detectors, gas chromatography-based methods, and few other methods. Finally, we tried to highlight the applicability, advantages and disadvantages of different pretreatment and analysis methods, and identified future prospects in this field.

Volatile Metabolic Markers for Monitoring Pectobacterium carotovorum subsp. carotovorum Using Headspace Solid-Phase Microextraction Coupled with Gas Chromatography-Mass Spectrometry

Identifying the extracellular metabolites of microorganisms in fresh vegetables is industrially useful for assessing the quality of processed foods. Pectobacterium carotovorum subsp. carotovorum (PCC) is a plant pathogenic bacterium that causes soft rot disease in cabbages. This microbial species in plant tissues can emit specific volatile molecules with odors that are characteristic of the host cell tissues and PCC species. In this study, we used headspace solid-phase microextraction followed by gas chromatography coupled with mass spectrometry (HS-SPME-GC-MS) to identify volatile compounds (VCs) in PCC-inoculated cabbage at different storage temperatures. HS-SPME-GC-MS allowed for recognition of extracellular metabolites in PCC-infected cabbages by identifying specific volatile metabolic markers. We identified 4-ethyl-5-methylthiazole and 3-butenyl isothiocyanate as markers of fresh cabbages, whereas 2,3-butanediol and ethyl acetate were identified as markers of soft rot in PCC-infected cabbages. These analytical results demonstrate a suitable approach for establishing non-destructive plant pathogen-diagnosis techniques as alternatives to standard methods, within the framework of developing rapid and efficient analytical techniques for monitoring plant-borne bacterial pathogens. Moreover, our techniques could have promising applications in managing the freshness and quality control of cabbages.

A diboronic acid fluorescent sensor for selective recognition of d-ribose via fluorescence quenching

Herein we reported a novel boronic acid-based water-soluble sensor. It decreased the fluorescence by 50% when combined with 0.0146 M of d-ribose, while increased or not changed obviously after binding to other carbohydrates.