Résumé
Fish fillets were simultaneously salted and dried by soaking in ternary solution (salt/com starch syrup) at low temperature (10°C). Optimal conditions for salting and drying fish were assessed. Salting and dewatering by OT combined with electrostatic smoking was patented and applied to differents fish fillets (salmon, herring, anchovy ... ). This combined process allows different advantages (e.g. short treatment time and compatibility with continuous process, energy saving, improvement of yield and productivity, limitation of effluents). For continous treatments, an original device has been proposed and patented, based on products showering with concentrated solutions. - Conventional salting/drying/smoking process (actual situation, problems encountered). Traditional cold smoking of fish fillets consists in three successives operations of salting, air drying and smoking. Salting is operated with pure dry salt or in brine in order to obtain product salt content of 2-3 %. The same oven is used for convection drying and smoking treatments and smoked (hard wood pyrolysis, oak or beech) is injected inside the oven and deposed naturally on the product. Each operation induces water loss (especially drying) in order to obtain a level of 10- 12 % at the end of the process.The whole process is well described by differents autors (Knockaert, 1990; Sainclivier, 1985 and Rutkowski, 1977) and calls upon several comments. Concerning salting, the use of pure salt allows a relativaly rapid salting, but one which is difficult to control and not very uniform. The water loss in the product, at this stage, is low, of the order of 2 %. The use of a brine enables the salting to be better controlled, but, in that case, the product loses only little or no water, which is detrimental for preservation thereof. Futhermore, the control of the sanitary quality of the brine which is generally weakly concentrated, is very delicate. The same applies to the processes in which the brine is added by injection. Concerning drying, the running cost is high, the different parameters of temperature, hygrometry and air speed having to be controlled and regulated with precision. The treatment temperature (between 20 and 30 °C) is favorable to the development of bacteria. In the whole process, treatment duration is long (4-12 hours depending of fillets size) and endproducts characteristics are non-homogeneous. (Résumé d'auteur)