While dried laver serves as an important raw ingredient for seaweed snacks, the microbial quality and safety risks associated with the preparation and processing of dried laver have not been well studied. In this project, three commercial laver processing plants were sampled from 2020 to 2022. Results indicated that the current washing and two-step drying process increased the microbial loads in dried laver. The total aerobic plate count (APC), coliform, and mold counts in dried laver ranged from 7.34 to 7.91, 2.12 to 3.87, and 1.65 to 3.87 Log CFU/g respectively. The study further explored the decontamination efficacy of four post-drying treatments (three nonthermal and one thermal treatments). Dielectric barrier discharge (DBD) plasma (150 kV, 10 min), UV-C radiation (40 cm, 30 min), ozone (150 ppm, 40 min), and hot air (150 degrees C, 30 min) reduced the APC and coliform levels by 2.10 and -1.12, 0.98 and 1.03, 2.12 and -2.87, and 3.00 and 2.24 Log CFU/g respectively. Unfortunately, Ozone and hot air treatments led to significant color change and nutrient losses. Microorganisms become harder to control once dried on food, future study should explore the use of pre-drying treatments to better enhance the microbial quality and safety of dried laver.

Roasted seaweed snacks are getting popular worldwide. To reveal the main origins of microorganisms present in the roasted seaweed snacks, samples of raw materials, finished products, and environment (both food-contact and nonfood-contact surfaces) were collected from four plants. The total aerobic plate (APC), coliform, and mold counts of these samples were analyzed and the selected samples were also used for 16S rRNA sequencing. Results showed that dried laver contained the highest levels of APC among all raw ingredients, ranging from 2.72 to 6.95 Log CFU/g. Crushed pumpkin seeds and almond flakes had the highest coliform (up to 5.57 Log CFU/g) and mold counts (up to 2.16 Log CFU/g). The addition of seasoning to seaweed sandwich snacks increased the total microbial loads. The roasting process decreased the APC, coliforms, and mold counts of seaweed snacks by 0.22–1.73 Log CFU/g, >0.18- >2.46 Log CFU/g, and >0.18- >0.88 Log CFU/g respectively. The 16S rRNA sequencing analysis showed that the microbiota of roasted seaweed snacks was closely correlated with that of dried laver and the microbial load of roasted sandwich seaweed was primarily from the dried laver while less from microorganisms present in the processing plant environment and line workers.