Abstract
Within Europe over the last 10 years, there has been an increase in seaweeds cultivated for human consumption. For food safety reasons, it is important to assess the microbiological and nutritional quality of the biomass. The fresh and dried edible seaweeds Alaria esculenta and Saccharina latissima were assessed over two consecutive years for the presence of microorganisms. Seaweed samples supplied from Scotland were stored under isothermal conditions for specific time intervals depending on the sample’s condition (fresh, dried or rehydrated). During storage, microbiological analyses were performed for the enumeration of Total Viable Counts (TVC), Pseudomonas spp., Enterobacteriaceae and Bacillus spp., as well as yeasts and molds. Additionally, bacterial colonies from the Marine Agar growth medium were isolated and subjected to PCR-RAPD analysis for characterization of the bacterial diversity of seaweeds. Bacterial isolates with different fingerprint patterns were further subjected to sequencing (16S rDNA, V1–V4 region). The presence of human pathogenic bacteria was also investigated. Results showed that the initial population of TVC was differentiated depending on the year of seaweed harvest, being closer to the enumeration limit (1.0 log CFU/g) in fresh samples from 2020 and higher in samples from 2019 (6.7 and 3.9 log CFU/g in A. esculenta and S. latissima, respectively). DNA-based analysis revealed the presence of Psychrobacter, Cobetia and Pseudomonas species in A. esculenta, while Psychrobacter and Micrococcus species were present in S. latissima.
Highlights
In the last 20 years, seaweed production has almost tripled, from 11 million tonnes in 2000 to 33 million tonnes in 2018 [1]
In Europe, the U.S and Canada, seaweed farming has focused on species such as Palmaria palmata, Alaria esculenta, Saccharina latissima and Laminaria spp., mainly for human consumption as well as for the production of hydrocolloids [4,5]
The protein content of either species was significantly higher in 2019 than in 2020, with 2.44 vs. 1.99 g/100 g and 1.40 vs. 0.87 g/100 g for fresh A. esculenta and S. latissima, respectively, with higher values in 2019 likely being explained by the more evident biofouling cover observed in this batch
Summary
In the last 20 years, seaweed production has almost tripled, from 11 million tonnes in 2000 to 33 million tonnes in 2018 [1]. In Europe, the U.S and Canada, seaweed farming has focused on species such as Palmaria palmata, Alaria esculenta, Saccharina latissima and Laminaria spp., mainly for human consumption as well as for the production of hydrocolloids (alginates, carrageenan, agar-agar) [4,5]. Despite its relatively low protein content compared to other seaweed species, it does contain essential amino acids along with several functional bioactive components [9,10]. This must be balanced against its high iodine content and the specific strategies needed to address this; as such, this is considered one of the main shortcomings of this species [11]. A. esculenta—amongst its other nutritional benefits—is rich in fucoxanthin, a high-value carotenoid pigment, mainly due to its antioxidant activities as well as its ability to control blood glucose levels [6]
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