A strategy of ultrasound-assisted processing to improve the performance of bio-based coating preservation for refrigerated carp fillets (Ctenopharyngodon idellus)

Effects of ultrasound-assisted chitooligosaccharides (COS-UA) coating on the quality attributes and microbial composition of refrigerated grass carp fillets were evaluated. The results showed that COS and COS-UA coatings retarded quality deterioration of fillets during storage. Compared to COS coatings, COS-UA treated samples had lower contents of BAs, simultaneously their levels of total volatile base nitrogen (TVB-N), K value and total viable counts (TVC) were further decreased by 13.6%, 4.2% and 7.8% on day 12, respectively. High-throughput sequencing showed that Aeromonas and Shewanella increased rapidly in control samples and became the main microbiota at day 12. By contrast, both coatings changed the microbial composition and reduced the proportion of spoilage organisms. Based on multiple evaluations, COS-UA extended shelf life of fillets by another 2 days when compared to COS. Therefore, ultrasonic treatment could be considered as an effective supplementary to improve the preservation effect of COS-based coatings for fresh preprocessed fish.

Effects of chitosan oligosaccharides on microbiota composition of silver carp (Hypophthalmichthys molitrix) determined by culture-dependent and independent methods during chilled storage

This study evaluated the effects of chitosan oligosaccharides (COS) on the changes in quality and microbiota of silver carp fillets stored at 4 °C. During storage, 1% (w/v) COS treated samples maintained good quality, as evidenced by retarding sensory deterioration, inhibiting microbial growth, attenuating the production of total volatile basic nitrogen, putrescine, cadaverine and hypoxanthine, and delaying degradation of inosine monophosphate and hypoxanthine ribonucleotide. Meanwhile, variability in the predominant microbiota in different samples was investigated by culture-dependent and -independent methods. Based on sensory analysis, shelf-life of silver carp fillets was 4 days for the control and 6 days for COS treated samples. Meanwhile, Pseudomonas, followed by Aeromonas, Acinetobacter, and Shewanella were dominated in the control samples at day 4 and contributed to fish spoilage at day 6. However, COS inhibited the growth of Pseudomonas, Aeromonas, and Shewanella significantly. Consequently, Acinetobacter followed by Pseudomonas became the predominant microbiota in COS treated samples at day 6. With the growth of Pseudomonas, COS treated samples were spoiled at day 8. Therefore, COS improved the quality of fillets and prolonged the shelf life of silver carp fillets by 2 days during chilled storage, which was mainly due to their modulating effects on microbiota.

Quality changes of salmon by-products during storage: Assessment and quantification by NMR

Safe utilization of fish by-products is an important task due to increasing fish consumption. It can provide new valuable food/feed and will increase the economical profit and sustainability of the fishery industry. NMR spectroscopy is a reliable tool able to monitor qualitative and quantitative changes in by-products. In this work the trichloroacetic acid extracts of salmon backbones, heads and viscera stored at industrially relevant temperatures (4 and 10°C) were studied using NMR. Twenty-five metabolites were detected and the possibility of salmon by-products utilization as a source of anserine, phosphocreatine and taurine was discussed. Statistical data elaboration allowed determining the main processes occurring during by-products storage: formation of trimethylamine and biogenic amines, proteolysis and different types of fermentations. By-products freshness was evaluated using a multi-parameter approach: the trimethylamine and biogenic amines concentration changes were compared with Ki and H-values and safe temperatures and times for storage of salmon by-products were proposed.

Biogenic amine production by Lactococcus lactis subsp. cremoris strains in the model system of Dutch-type cheese

The aim of this study was to compare the biogenic amine production of two starter strains of Lactococcus lactis subsp. cremoris (strains from the Culture Collection of Dairy Microorganisms - CCDM 824 and CCDM 946) with decarboxylase positive activity in a model system of Dutch-type cheese during a 90-day ripening period at 10°C. During ripening, biogenic amine and free amino acid content, microbiological characteristics and proximate chemical properties were observed. By the end of the ripening period, the putrescine content in both samples with the addition of the biogenic amine producing strain almost evened out and the concentration of putrescine was >800mg/kg. The amount of tyramine in the cheeses with the addition of the strain of CCDM 824 approached the limit of 400mg/kg by the end of ripening. In the cheeses with the addition of the strain of CCDM 946 it even exceeded 500mg/kg. In the control samples, the amount of biogenic amines was insignificant.