Low-temperature drying of salted cod (Gadus morhua) assisted by high power ultrasound: Kinetics and physical properties

• Published in: Innovative food science & emerging technologies 2014-06, Vol.23, p.146-155
• Main Authors: Ozuna, César, Cárcel, Juan A., Walde, Per M., Garcia-Perez, Jose V.
• Format: Article
• Language: English
• Subjects: Color; Dehydration; Gadus morhua; Microstructure; Non-thermal processing; Texture; Ultrasonic
• ISSN: 1466-8564; 1878-5522
• DOI: 10.1016/j.ifset.2014.03.008

Low-temperature convective drying could be considered an affordable alternative to conventional freeze-drying for foodstuffs. The process intensification should be based on non-thermal technologies, such as power ultrasound. Thereby, the aim of this work was to evaluate the air-borne application of power ultrasound on the low-temperature drying of salted cod. For that purpose, drying experiments were carried out at −10, 0, 10 and 20°C on salted cod slices at 2m/s with (AIR+US, 20.5kW/m3) and without ultrasonic application (AIR). In the dried-salted cod, its rehydration capacity was analyzed, as were the microstructural, textural and color changes. At every temperature tested, ultrasound application increased the drying rate; thus, an average increase of 74% was observed in the effective diffusivity. AIR+US dried samples were softer and exhibited a higher rehydration capacity than AIR ones, which was linked to the microstructural changes produced by ultrasound. In addition, color changes were induced by ultrasound application. Nowadays, low-temperature convective drying represents a promising alternative for the production of high-quality dried products. However, this technology is mostly limited by the low drying rate, which retards the dehydration process and directly increases the processing costs. Power ultrasound, a non-thermal technology, represents an interesting alternative means of improving low-temperature convective drying due to the fact that acoustic (mechanical) waves may affect water removal during drying with a low heating capacity. Thereby, the ultrasonically enhanced low-temperature convective drying could constitute an affordable alternative to lyophilization (or freeze-drying), which is mainly restricted to high-quality food commodities. •Power ultrasound (US) was used for improving low-temperature drying of salted cod.•US quickened the drying kinetics, shortening the drying time by up to 50%.•The increase in the effective diffusivity produced by US reached 110%.•US promoted changes in dried-salted cod structure.•US increased the lightness of dried-salted cod, which is a relevant quality trait.