Combined hurdle effects of pulsed electric field and ultraviolet-C irradiation on microbial load reduction and composition of hemeproteins from Asian seabass gills

Abstract

The combined effects of two non-thermal technologies, namely pulsed electric field (PEF) and ultraviolet-C (UV–C) irradiation, on microbial load reduction and composition of crude hemeprotein extract (CHPE) from Asian seabass gills were investigated. PEF at two intensities (15 kV and 17.5 kV) for different times (0, 1, 2.5, 5 and 10 min) was employed to treat CHPE solution. Subsequently freeze-dried PEF treated powders were exposed to UV-C for varying durations (0, 15 and 30 min). Microbial community in gill and selected CHPE powders was also determined using next generation sequencing (NGS). PEF treatment effectively reduced the initial microbial load (8.0 log₁₀ CFU/g) when high PEF intensity (17.5 kV) for longer treatment time (5 min) was employed, leading to microbial load reduction to 5.5 log₁₀ CFU/g. However, prolonged PEF treatment adversely affected CHPE properties, as witnessed by the decreased heme iron content and alterations in protein patterns. Subsequent UV-C irradiation of freeze-dried PEF-treated CHPE powder for 15 min demonstrated a synergistic effect on further reduction of microbial counts to 3.0 log₁₀ CFU/g. NGS analysis showed the dominance of Flavobacteriaceae families in the microbial community composition in gill, untreated CHPE powder and PEF-UV-C treated CHPE powder. Nevertheless, no Vibrio parahaemolyticus and other Vibrio spp. were detected in all samples. The study revealed the potential of combined non-thermal hurdle technologies, under appropriate conditions, in ensuring microbiological safety and maintaining quality of CHPE. CHPE powder could therefore be used for fortification in food products as an iron supplement to alleviate iron-deficient anemia.