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

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

Characterization of the spoilage microbiota of hake fillets packaged under a modified atmosphere (MAP) rich in CO2 (50% CO2/50% N2) and stored at different temperatures

The aim of this study was to characterize the spoilage microbiota of hake fillets stored under modified atmospheres (MAP) (50% CO2/50% N2) at different temperatures using high-throughput 16S rRNA gene sequencing and to compare the results with those obtained using traditional microbiology techniques. The results obtained indicate that, as expected, higher storage temperatures lead to shorter shelf-lives (the time of sensory rejection by panelists). Thus, the shelf-life decreased from six days to two days for Batch A when the storage temperature increased from 1 to 7 °C, and from five to two days—when the same increase in storage temperature was compared—for Batch B. In all cases, the trimethylamine (TMA) levels measured at the time of sensory rejection of hake fillets exceeded the recommended threshold of 5 mg/100 g. Photobacterium and Psychrobacter were the most abundant genera at the time of spoilage in all but one of the samples analyzed: Thus, Photobacterium represented between 19% and 46%, and Psychrobacter between 27% and 38% of the total microbiota. They were followed by Moritella, Carnobacterium, Shewanella, and Vibrio, whose relative order varied depending on the sample/batch analyzed. These results highlight the relevance of Photobacterium as a spoiler of hake stored in atmospheres rich in CO2. Further research will be required to elucidate if other microorganisms, such as Psychrobacter, Moritella, or Carnobacterium, also contribute to spoilage of hake when stored under MAP