Effects of blue LED irradiation on the quality characteristics of Mukeunji, a long‐term fermented kimchi, during refrigerated storage

Abstract

This study investigated the effects of blue light emitting diode (BLED) irradiation on the quality characteristics of Mukeunji (long‐term fermented kimchi). Mukeunji kimchi broth (MKB) was treated with 460 nm BLED (irradiance 375 J/s∙m2) under refrigerated storage conditions. The effects of BLED irradiation on microbial growth were evaluated over the 3‐day storage period at 4°C. The quality attributes of the MKB, including color, pH, and antioxidant activity, were also assessed during the storage period. No significant difference was observed in the viable counts of lactic acid bacteria between BLED‐treated and BLED‐untreated samples. The yeast and mold counts in the MKB, however, were significantly reduced after 24 hr of BLED treatment at 4°C. The MKB pH significantly increased after 72 hr of BLED treatment at 4°C. The hunter redness (a*) was retained in BLED‐treated samples, whereas the yellowness (b*) was reduced in all samples. After BLED irradiation for 24 hr, significant changes in the 2,2′‐azino‐bis‐3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS) radical scavenging activity of the MKB were also observed. The MJ1 and MJ2 strains isolated from MKB showed high sequence homology with Bacillus paralicheniformis and Bacillus velezensis, respectively, with 99% similarity or more in the phylogenetic tree. Chlorophyll pigment absorbs the blue light emitted by the BLED, so it can partially reduce the growth inhibitory effect of BLED irradiation on the two isolates. These findings suggest that BLED treatment can potentially modulate microbiological growth in Mukeunji during refrigerated storage without significant detriment to its characteristic properties.