Ultrasonically assisted low-temperature drying of desalted codfish

Abstract

[EN] Low-temperature drying (LTD) constitutes an interesting means of dehydrating foodstuffs, thus preserving the quality of the product. Power ultrasound (US) generates several mechanical effects that could help to shorten the long drying times associated with LTD. In this work, the feasibility of using US in LTD of desalted cod was assessed. For this purpose, desalted cod slices (50 30 5 mm) were dried (2 m/s) at different temperatures (10, 0 and 10 C) without (AIR) and with (AIR þ US, 20.5 kW/m3) US application. Afterwards, the dried samples were rehydrated in distilled water (25 C). A diffusion model was used to describe both drying and rehydration kinetics. The color and hardness of both dried and rehydrated cod samples were also measured. The application of US increased the drying rate at every temperature tested, shortening the drying time by 16% at 0 C and up to 60% at 10 C. The ultrasonically assisted dried samples presented a rehydration rate which was slightly lower than that of those that had been conventionally dried, but they were harder and whiter, which is more suited to consumer preferences. Therefore, power ultrasound could be considered an affordable technology with which to accelerate LTD of desalted cod, providing high quality dried products.