The effect of slaughtering methods on actin degradation and on muscle quality attributes of farmed European sea bass (Dicentrarchus labrax)

The Effect of Sodium Bicarbonate Injection on the Physico-Chemical Quality of Post-Harvest Trout

The muscle hardness of fish is an important parameter associated with meat quality, and the post-mortem decrease in the pH of fish tissue pH affects its physical properties. We hypothesized that maintaining a high pH in fish tissue after death would prevent protein denaturation and consequent textural deterioration. This study aimed to determine the effectiveness of sodium bicarbonate (SBC) injections in preventing tissue softening caused by low pH after death in trout. We injected varying molar concentrations of SBC in rainbow trout (Oncorhynchus mykiss; 0 M, 0.5 M, 0.75 M, and 1 M) after harvest, and the product quality was assessed at 0, 24, 48, 72, and 96 h of ice storage. Quality was evaluated using proximate analyses for color, pH, water holding capacity (WHC), texture profile, and rigor index. The 0 M group had the lowest pH, and the 0.75 M group had the highest pH at all time points during storage. We observed improved tissue texture during storage in fish treated with 0.75 and 1 M SBC. The texture profile analysis showed higher hardness, frangibility, and stickiness in the tail than in the other regions. These varying results can be explained by significant differences between parts of the fish and sampling point selection. We also observed the highest pH and WHC values in the groups injected with 0.75 and 1 M SBC during storage.

Skin immune response to Aeromonas hydrophila infection in crucian carp Carassius auratus revealed by multi-omics analysis

Fish skin is an essential protective barrier and functions as the first line of immune defense against pathogens. However, the molecular mechanism at the proteome-level remains unclear in the skin of fish. In this study, the comparative proteomics of skin immune responses of crucian carp Carassius auratus infected with Aeromonas hydrophila was investigated by isobaric tags for relative and absolute quantification (iTRAQ), two-dimensional gel electrophoresis combined with mass spectrometry (2-DE/MS) as well as high-throughput transcriptome (RNA-seq) techniques. A total of 241 and 178 differentially expressed proteins (DEPs) at 6 and 12 h post-infection (hpi) were respectively identified by iTRAQ, and key-DEPs were furtherly verified with 2-DE/MS analysis. GO and KEGG analysis showed that these DEPs were mostly related to metabolism, regulation of the cytoskeleton, stress and immune responses. Co-association results of proteome and transcriptome revealed the lysozyme (LYZ), complement C3, DnaJ (Hsp40) homolog subfamily C member 8 (DNAJC8) and allograft inflammatory factor 1-like (AIF1L) play important roles in skin immune responses of crucian carp. The significantly up-regulated expression of detected immune-related genes (c3, mapk3, f5, nlr, hsp90, itgb2, fnl, flnca, p47, mhc and pros1) were validated by qRT-PCR analysis. To our knowledge, this is first report on multi-omics analysis of the differential proteomics for the skin immune response of C. auratus against A.hydrophila infection, which contribute to the understanding the mechanisms of skin mucosal immunity in cyprinid fish.

Molecular signatures of beef tenderness: Underlying mechanisms based on integromics of protein biomarkers from multi-platform proteomics studies

Over the last two decades, proteomics have been employed to decipher the underlying factors contributing to variation in the quality of muscle foods, including beef tenderness. One such approach is the application of high-throughput protein analytical platforms in the identification of meat quality biomarkers. To broaden our understanding about the biological mechanisms underpinning meat tenderization across a large number of studies, an integromics study was performed to review the current status of protein biomarker discovery targeting beef tenderness. This meta-analysis is the first to gather and propose a comprehensive list of 124 putative protein biomarkers derived from 28 independent proteomics-based experiments, from which 33 robust candidates were identified worthy of evaluation using targeted or untargeted data-independent acquisition proteomic methods. We further provide an overview of the interconnectedness of the main biological pathways impacting tenderness determination after multistep analyses including Gene Ontology annotations, pathway and process enrichment and literature mining, and specifically discuss the major proteins and pathways most often reported in proteomics research.

Changes on the Development of Rigor Mortis in Cultured Tilapia (Oreochromis niloticus) Fed with a Mixture of Plant Proteins

In recent years it has been pointed out that the feed of farmed fish has an effect on the quality of the final product. Therefore, this study evaluated the effect of fishmeal (FM) replacement by a mixture of plant protein (MPP) on the development of rigor mortis of tilapia (Oreochromis niloticus). One hundred and twenty fish at an initial average weight of 123 ± 6.3 g were fed with three extruded isonitrogenous and isolipidic 6.2% crude lipids experimental diets, in which FM were replaced by 0% (D0), 50% (D50), and 100% (D100) of MPP (soybean meal, corn meal, wheat meal, and sorghum meal). A reference diet (DC) containing FM as the main protein source was used as a control. The fish were divided into triplicate groups per dietary treatment. The experiment was conducted in a tank system at 26.8°C water temperature for 67 days. The chemical composition of experimental diets and muscle were determined. The glycogen, adenosine 5′-triphosphate (ATP) and related compounds, pH, shear force, and rigor index (RI%) were monitored during storage on ice for 48 h. The results indicated that FM replacement affected (p≤0.05) the muscle composition, where the fish fed with D100 presented the higher content of lipids and ash. Fish fed with D0 and DC presented a more pronounced onset of rigor mortis and also showed a higher IR%, a lower content of glycogen, ATP, adenosine 5′-diphosphate (ADP), adenosine 5′-monophosphate (AMP), pH, and shear force. The changes in chemical composition of muscle and other parameters evaluated indicated that FM replacement increases energy reserves (glycogen, ATP, ADP, and AMP) which delayed the onset of rigor mortis, as well as a lower pH and shear force in the muscle of tilapia. Therefore, the substitution of FM by MPP could contribute to delaying the onset of rigor mortis and with this, the quality and shelf life of tilapia could be increased.

The impact of stunning methods on stress conditions and quality of silver carp (Hypophthalmichthys molitrix) fillets stored at 4°C during 72h postmortem

This study aimed to evaluate different stunning methods [percussion (T1), immersion in ice/water slurry (T2), and gill cut (T3)] on quality and stress conditions of silver carp (Hypophthalmichthys molitrix) fillets stored at 4°C in 72h postmortem. Rigor index (RI%), behavioral analysis, levels of lactic acid and muscle glycogen were measured for stress level evaluation. Meanwhile, sensory assessment, texture properties, cooking loss, adenosine triphosphate (ATP) related compounds, adenosine monophosphate deaminase (ADA) activity, and acid phosphatase (ACP) activity were analyzed. The least stress condition, significantly (P<0.05) higher initial glycogen content was observed in T1. Ice/water stunning reduced the rate of ATP degradation, reflected in the lowest K value during 72h. Aversive behaviors, significantly (P<0.05) higher cooking loss, hypoxanthine riboside (HxR) content, and lower sensory score were observed in T3. The results indicated that gill cut in aquatic processing industry should be avoided for inferior quality and aversive reactions during stunning.