Τhe popularity of ready-to-eat raw fish (such as sushi and sashimi) has been significantly increased over the last decade. Raw fish is very appreciated worldwide and has become a major component of human diet because of its fine taste and nutritional properties. Possible hazards concerning fish safety and quality are classified as biological and chemical hazards . They may be contaminants (mainly bacteria and parasites) that often accumulate in edible tissue of fish and transmit to humans via the food chain affecting the consumer’s health (Lehen et al., 2020) . The perception of health, quality and safety benefits is considered as one of the motivational factors that could explain fish consumption patterns; however, the issue of perceived convenience or discomfort of fish has often emerged as influential in consumer choice too (Masi et al., 2022).
The objective of the study was to establish a verification method for the absence of live parasites in farmed fish, to evaluate and define the quality and safety standards of whole fresh fish and fish fillets, and finally to design an efficient production and transportation/storage system for ready-to-eat raw fish obtained from the Greek aquacultures. The results were validated in actual fish production environment by implementing a standard production plan to control the potential risks (bacterial and parasitic infections) while retaining the high quality in terms of microbial spoilage and sensory profiling . The proposed protocol for the verification of absence of contaminants, expected to exclude farmed fish in Greece from the obligation of prior freezing fisheries products, intended to be consumed raw or undercooked according to Reg. (EEC) 853/2004. Currently the part of the assessment for bacterial contaminants and the validated self-life predictive model will be presented.
Materials and methods
Fish (gilthead seabream, European sea bass, red sea bream and meagre) was harvested from 6 different fish farms within the period November 2022- February 2023 from western Greece (Thesprotia and Kefallonia), central Greece (Phthiotida), northeastern Greece (Lesvos) and southeastern Greece (Rhodes). 80 fish from each batch was delivered to the Agricultural University of Athens (Department of Food Science and Human Nutrition, Laboratory of Food Process Engineering) for quality evaluation and shelf life modelling. Time and temperature was continuously monitored from harvesting upon receipt of samples at the laboratory for shelf life evaluation, using electronic data loggers (RC-5 USB temperature recorders, Elitech, London, United Kingdom) . Quality evaluation was based on microbial spoilage (enumeration of total viable count, Pseudomonas spp. and Enterobacteriaceae) and sensory evaluation. Bacterial microbiota of fish flesh initially and during refrigerated storage was characterized by 16S metagenomic analysis. A sample of 600 fish (450 European sea bass and 150 Meagre) from 4 different fish farms was delivered to the Hellenic Centre for Marine Research for microscopic and molecular parasite examination.
Initial microbial load of fish flesh (without skin - skinless ) ranged 2.4-4.6 logCFU /g for total viable count (N=50). The required time from harvesting to the delivery of fish to the laboratory for shelf life evaluation was 2.5-52.5 hours and the effective temperature during harvesting and transportation ranged 0.2-1.6°C. A logarithmic equation was developed to describe the effect of time and temperature during harvesting and transportation of fish on the microbial load of fish flesh. Based on the shelf life experiments, the dominant spoilage microflora in fish stored at 2 and 4°C was Pseudomonas spp. , in agreement with relevant studies on Mediterranean fish stored aerobically at refrigerated conditions (Gram and Huss, 1996; Papaharisis et al., 2019; Koutsoumanis and Nychas, 2000).
Discussion and conclusion
The definition of the dominant microflora and the development of a validated shelf-life predictive model is a prerequisite for the definition of the spoilage process and the quality and safety assurance of ready-to-eat raw fish products . A fish production system has been provided in the form of a detailed guide for fish farms and processing facilities, to ensure the availability of safe and high quality ready-to-eat raw farmed fish and develop distribution channels with focus on export market Mediterranean and the European region.
This study was supported by the Hellenic Aquaculture Producers Organization (HAPO) https://fishfromgreece.com/
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