Time-temperature exposure of fresh fish in the commercial chain

Fresh fish is a very precious and delicate commodity. Testing/modelling of the shelf life of fresh European Sea bass (Dicentrarchus labrax), with reference to its thermal history in the commercial chain, was approached by means of a new kind of small temperature recording devices, directly placed in the fish meat and/or in the storage rooms. Twenty selected “real” thermal histories were so collected and split into the different steps experienced during the commercial life (storage at manufacturer, delivery, storage in retail cells, exposition in retail counters). The fish remains at temperatures lower than 1°C during the first steps of the commercialisation and reaches 5°-8°C during the exposition at the sale point: this step is also the longest one (3-5 hours). The obtained data were statistically analysed and plotted on time-temperature exposure probability charts (50%, 75%, 90% probability values were considered). Delivery at the sale points resulted as the critical step because of the poor control of product temperature and the influence of ambient conditions. Collected data were also employed to parameterise the shelf life: a suitable hypothesis was applied to work out the integration of the most probable time-temperature exposure history. Our findings (75% of the cases) showed that the expected shelf life (or “freshness”) just after the purchase of fresh fish was 60% of the whole one. This condition can be related to an integration average temperature of 4°C, considering 2 days of commercialisation time. Furthermore, our results showed that freshness can be maintained for 1-2 days more during the storage at home. The average exposure temperature could be then reduced by 1-2°C with a joined effort (manufacturer, sale point management, consumer advertising) thus extending the fresh fish shelf life up to 4-5 days.