Impact of high pressure treatment on shelf life and microbial profile of wild harvested Ascophyllum nodosum and aquacultured Alaria esculenta during storage

Abstract

Fresh seaweeds, Alaria esculenta and Ascophyllum nodosum, are brown macroalgae species recognised as an excellent source of macro- and micronutrients. Providing novel approaches for ensuring the microbiological safety of this product is important to guarantee the preservation of the nutritional values. In this study, these two species were treated with high pressure, as well as traditional preserving methods (dry salt, and hot water blanching) followed by a storage process to evaluate the effect on the microbiological content and the microbiota profile was investigated after different treatments. High pressure treatments were introduced in order to avoid the salt addition or nutrients loss during conventional seaweed preservation methods.In general, high pressure (500 MPa) treated fresh seaweeds with 4 °C storage temperature still have acceptable total viable counts around 3 log cfu/mL after 30 days. 16S rDNA profiling revealed an average of 3059 operational taxonomic units (OTUs) across all the seaweeds analysed. The top four dominant phyla were Cyanobacteria, Proteobacteria, Firmicutes and Bacteroidota. Cyanobacteria dominated bacteria communities in A. esculenta samples, while Proteobacteria were predominant in A. nodosum samples. In this study, HPP did not cause significant variation of the diversity of microbiome profile but changed the relative abundance of different phyla, including Cyanobacteria, Fermicutes, Bacteriodota and Verrucomicrobia.