Post-drying decontamination of laver by dielectric barrier discharge plasma, UV radiation, ozonation, and hot air treatments

Abstract

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 non-thermal 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 °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.