The current study investigated the synergistic effects of NaOCl (50-200 ppm)/ultrasound (37 kHz, 380 W for 5-100 min) combination on the reduction of Escherichia coli and Bacillus cereus in raw laver. The synergistic reductions were not dependent on concentrations of NaOCl and times of ultrasound. Synergistic reduction ranged from 0.1 to 0.5 log10 colony-forming units (CFU)/g and 0.1-1.1 log10 CFU/g, respectively, for E. coli and B. cereus, with the largest synergistic reduction in the combination of 200 ppm NaOCl and 60-min ultrasound. Moreover, significant differences of "L" (lightness), "a" (redness), and "b" (yellowness) were not observed in combined with 50-200 ppm NaOCl and 100-min ultrasound compared to those in raw laver treated by only 100-min ultrasound. The results in the current study indicate that the combined treatment of 200 ppm NaOCl and 60-min ultrasound could be regarded a potential optimum hurdle approach in the seaweed production, processing, and distribution process to enhance seaweed safety.

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Use of hydrogen peroxide against Escherichia coli on surfaces based on concentration and time using response surface methodology was studied. Models for E. coli reduction were developed for stainless steel, ceramic, plastic, glass, rubber, and wood treated at 1,100 ppm for 5 min. Reduction values of E. coli were 1.68, 1.33, 1.31, 1.28, 1.24, and 1.14 log CFU/cm 2 . All models were significant (p<0.05). Lack-of-fit values were non-significant. r 2 values were close to 1 with p<0.05. The effect was insufficient to meet guidelines. An increase in the concentration or the exposure time is needed to sanitize food contact surfaces.