Eco-innovative possibilities for improving the quality of thawed cod fillets using high-power ultrasound

Abstract

In order to improve the quality of thawed cod fillets and minimize the impact of processing, an extended hydration phase is applied in the fishery product industry in order to recover the water lost during freezing and thawing. Such long phases not only compromise productivity, but increase the chances of microbial growth in fish. Ultrasound (US) is a technology that could reduce these long hydration times, thanks to its capacity to improve mass-transfer processes, thereby limiting the development of fish microbiota.This investigation studies the effect of different US intensities (25 kHz, 29.4 W/kg to 2.9 W/kg, 113.7 to 15.3 W) on weight gain (WG) in the hydration process of cod fillets. The influence of the hydration medium's pH (from pH 8.5 to 10.5) in combination with US was likewise evaluated. Microbiological and sensory analyses were carried out at the end of the hydration process in order to evaluate its impact.The higher the applied US power, the lower was the WG. US intensities of 2.9 W/kg produced the highest increments in WG (18.6%), reducing hydration time by 33% and thereby achieving the same hydration values as in control samples. The combination of US with a controlled pH of 8.5 permitted to shorten hydration time by an additional day, and also led to improved microbial quality in comparison with control samples. Sensorial analyses indicated that after 5 d of hydration, Quality Index Method (QIM) values were better than those obtained for control samples after 5 and 7 d. Specifically, color and gaping were the sensorial attributes of cod fillets better protected with the application of US.