Abstract
The light-emitting diode (LED) has been widely used in the food industry, and its application has been focused on microbial sterilization, specifically using blue-LED. The investigation has been recently extended to characterize the biotic and abiotic (photodynamic) effects of different wavelengths. Here, we investigated LED effects on kimchi fermentation. Kimchi broths were treated with three different colored-LEDs (red, green, and blue) or kept in the dark as a control. Multiomics was applied to evaluate the microbial taxonomic composition using 16S rRNA gene amplicon sequencing, and the metabolomic profiles were determined using liquid chromatography–Orbitrap mass spectrometry. Cell viability was tested to determine the potential cytotoxicity of the LED-treated kimchi broths. First, the amplicon sequencing data showed substantial changes in taxonomic composition at the family and genus levels according to incubation (initial condition vs. all other groups). The differences among the treated groups (red-LED (RLED), green-LED (GLED), blue-LED (BLED), and dark condition) were marginal. The relative abundance of Weissella was decreased in all treated groups compared to that of the initial condition, which coincided with the decreased composition of Lactobacillus. Compositional changes were relatively high in the GLED group. Subsequent metabolomic analysis indicated a unique metabolic phenotype instigated by different LED treatments, which led to the identification of the LED treatment-specific and common compounds (e.g., luteolin, 6-methylquinoline, 2-hydroxycinnamic acid, and 9-HODE). These results indicate that different LED wavelengths induce characteristic alterations in the microbial composition and metabolomic content, which may have applications in food processing and storage with the aim of improving nutritional quality and the safety of food.
Highlights
Increasing attention has been paid to various functional foods, including kimchi, which is expected to improve health status and prevent diseases (e.g., COVID-19)
We first evaluated alpha diversity via Ace, Chao, Jackknife, Shannon, and Simpson indexes based on the results of incubation with different light-emitting diode (LED) treatments (72 h) (Table S1)
We investigated the effects of different wavelengths of LED
Summary
Increasing attention has been paid to various functional foods, including kimchi, which is expected to improve health status and prevent diseases (e.g., COVID-19). The quality and characteristics of kimchi are determined by the microbial community originating from vegetables and subsidiary materials. Among the kimchi microbial community, probiotics are dominant, the following three genera: Lactobacillus, Leuconostoc, and Weissella [9,10,11,12]. By changing these multiple factors, different combinations of taste and flavor can be acquired, forming various types of fermented kimchi to meet diverse consumer preferences. People prefer commercially available kimchi more than making their own, owing to lifestyle changes (e.g., increases in numbers of single-person households) according to the Korea Agro-Fisheries & Food Trade Corporation (2019). As commercial kimchi is manufactured through natural fermentation without using a separate sterilization process, specific care should be taken for raw material management, and proper storage methods should be used to control undesired fermentation by other types of microorganisms
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