Application of electron beam irradiation for improving the microbial quality of processed laver products and luminescence detection of irradiated lavers

Abstract

The laver (Porphyra spp.) is normally processed in three kinds of products: dried laver (DL), roasted laver (RL), and seasoned roasted laver (SL). This work evaluated the effects of electron beam (E-beam) irradiation at different doses (0, 1, 4, 7, and 10 kGy) on microbiological and physicochemical qualities and detection characteristics of irradiated samples by luminescence analysis. E-beam irradiation resulted in dose-dependent microbial reductions, showing that 1 kGy destroyed initial coliforms (< 2.35 log CFU/g) to undetectable levels (< 10 CFU/g), while 7 kGy (approved dose for seaweed in Korea Food Code) reduced total aerobic bacteria (3.72–6.33 log CFU/g) and yeasts and molds (2.05–4.98 log CFU/g) by about 2 log cycles. Chlorophyll content remained unaffected in irradiated samples as compared to control; however, carotenoids content and Hunter’s b values (degree of yellowness) showed a tendency to decrease in a dose-dependent manner (p < 0.05). However, E-beam irradiation less than 7 kGy did not significantly affect sensory properties of the processed laver products. Irradiated laver products (DL, RL, and SL) could be screened and detected by analyzing photostimulated luminescence and thermoluminescence, respectively, from the non-irradiated ones. The overall results indicated that E-beam irradiation is effective for ensuring the improved microbial quality (< 4 log CFU/g) for the exporting processed laver products without apparent quality changes.