Ultrasonically enhanced desalting of cod (Gadus morhua). Mass transport kinetics and structural changes

Abstract

The search for an alternative means of reconstituting dried and salted products prior to consumption is of relevance for the food industry. New techniques should speed up the process while causing minimum impact on product quality. Thereby, the aim of this work was to evaluate both the effect of high-intensity ultrasound application on the desalting kinetics of cod, as well as the changes in its textural and microstructural properties. Moisture and NaCl transport was studied separately by taking the diffusion theory into account. The evolution in the swelling and hardness of cod during desalting was determined and modeled by assuming first-order kinetics. A microstructural analysis of raw salted and desalted cod was also carried out by means of light microscopy and SEM techniques. Ultrasound application significantly (p < 0.05) affected both moisture and NaCl transport and the increase in both effective diffusivities (from 24% to 103%) was linked to the acoustic pressure applied. The desalting process induced the swelling and the softening of the cod tissue, both of which are phenomena that are intensified by ultrasound application. From the microstructural observations, it was shown that the application of highintensity ultrasound modified the cod structure, e.g. the increase in the fiber width.