Unravel the formation of high microbial load of dried laver by microbial level and microbiota analysis of the laver production line

To better understand the formation of high microbial level in the processing of dried laver also known as nori (Porphyra yezoensis), this study analyzed the aerobic plate count (APC), coliform, and microbial diversity of dried laver production line. From December 2023 to April 2024, the processing water, laver materials and food contact surfaces (FCS) samples were collected from three processing plants. The results showed that shredding, sponge dehydration and first drying all significantly promoted the microbial level of laver. The U trend change with seasons of coliform level in laver samples after shredding was consistent with the seasonal change of temperature in the workshop. The FCS such as sponge were detected with a high APC level (5-8 Log CFU/g) and coliform level (1.5-3 Log CFU/g). Cross contamination was confirmed with increase (1-2 Log CFU/g) of the APC of laver readily after sponge dehydration. The microbiota of laver before drying is vulnerable but consistent after drying. This study provided novel insights for developing microbial control strategy in dried laver process industry.