Effect of a collagen peptide-fish oil high internal phase emulsion on the printability and gelation of 3D-printed surimi gel inks.

The effect of a high internal phase emulsion (HIPE) on three-dimensional-printed surimi gel inks was studied. Increasing the concentration of collagen peptide decreased the particle size of HIPE droplets and improved the viscoelasticity and stability. For example, when the collagen peptide concentration was 5 wt%, the viscoelasticity of the HIPE was high, as indicated by the presence of small and uniform particles, which formed a monolayer in the outer layer of the oil droplets to form stable a HIPE. A HIPE was used as the filling material to fill the surimi gel network, which reduced the porosity of the network. Surimi protein and peptides have dual emulsifying effects on the stabilization of oil. After adding the emulsion, the texture, gel properties and rheological properties of the surimi were reduced, and its printing adaptability was improved. This study provides new ideas for the production of surimi and its application in 3D printing.

Quantitative modelling reservoir microalgae proliferation in response to water-soluble anions and cations influx.

Atmospheric precipitation deposits acid-forming substances into surface water. However, the effects of water-soluble components on microalgae proliferation are poorly understood. This study analysed the growth characteristics of three microalgae bioindicators of water quality: Scenedesmus quadricauda, Chlorella vulgaris, and Scenedesmus obliquus, adopting on-site monitoring, culture experiments simulating 96 types of water by supplementing anions and cations, and predictive modelling. The result quantified pH > 3.0 rain with dominant Ca2+, Mg2+, and K+ cations, together with anions of NO3- and SO42-. The presence of Ca2+ of up to 0.1 mM and Mg2+ concentrations (>0.5 mM) suppressed Scenedesmus quadricauda growth. Soluble ions, luminosity, and pH had significant impacts (p ≤ 0.01) on increased microalgae proliferation. A newly proposed microalgae growth model predicted a 10.7-fold increase in cell density six days post-incubation in the case of rainfall. The modelling supports algal outbreaks and delays prediction during regional water cycles.

Analysis of the water state and microfractal dimension of tilapia fillets during freezing and thawing.

To study the effects of freezing and thawing times and freezing temperatures on the water state and microstructure of tilapia fillets, experiments on tilapia fillets were carried out at -4 and -18°C with one to four freezing and thawing cycles (FTCs). Low-field nuclear magnetic resonance (LF-NMR) and nuclear magnetic resonance imaging were used to observe the water state after different treatments, and scanning electron microscopy (SEM) and frozen sections were used to observe the microstructure changes. Fractal dimension (FD) was used to quantitatively characterize the microstructure of the fish tissue, and the correlation between FD and fish fillet quality parameters was studied by principal component analysis (PCA). The findings showed that with the increase of FTCs, the thawing loss increased, and the water holding capacity (WHC) fell. FTCs cause a decrease in immobilized water and an increase in free water in the fillet. This indicates the migration of immobilized water to free water. SEM and frozen slice images showed that the growth of ice crystals led to the destruction of myogenic fibers. A decrease in freezing temperature inhibited ice crystal growth. The FD value dropped in accordance with an increase in FTCs. PCA demonstrated that the WHC, NMR data, and FD value had a strong correlation with the quality changes in the tilapia fillets. Therefore, FD and water state can reflect the quality characteristics of tilapia fillets. PRACTICAL APPLICATION: The water migration in tilapia fillets is detected with LF-NMR, and the microscopic image may be quantified using the FD value. Both approaches can offer fresh perspectives on how to assess the quality of tilapia fillets and reflect changes in their quality.

The effects of polyphenols on fresh quality and the mechanism of partial freezing of tilapia fillets.

BACKGROUND: Fish is one of the most popular foods for consumers because of its abundant nutrition, tenderness and delicious taste. With increasing demand for tilapia fillets, practical preservation is widely used to maintain quality and safety during long-distance transportation and storage. Thus the effects of polyphenols (2 g L-1 ) on color, flavor quality and mechanism of tilapia fillets were studied during 49 days of partial freezing (-4 °C). RESULTS: Treatment with carnosic acid (CA), procyanidin (PA), quercetin (QE) and resveratrol (RSV) inhibited water migration, myoglobin oxidation and psychrophilic bacteria stability during partial freezing storage. Aeromonas and Acinetobacter were the dominant bacteria of tilapia fillets during -4 °C storage. The relative abundance of aromatic substances (T70/2) in the polyphenol groups (>20%) was richer than in the control (CON) group (17%). Partial least squares discriminant analysis results showed that the different odors of the control and polyphenol groups were completely separated. Moreover, 35 fatty acids were identified by gas chromatographic analysis. On 49 days, the ratios of unsaturated fatty acids in the PA group (58.64%), QE group (57.70%) and RSV group (57.25%) were higher than in the control group (57.19%), and the PA group was the highest. CONCLUSION: Polyphenol treatment effectively maintained freshness and improved the quality of tilapia fillets during partial freezing. The polyphenol treatment comprehensively sustained the color and flavor quality of tilapia fillets found in the proposed mechanism. In particular, PA treatment was considered a potential method for preserving the freshness of fillets. © 2022 Society of Chemical Industry.

Impact of the magnetic field-assisted freezing on the moisture content, water migration degree, microstructure, fractal dimension, and the quality of the frozen tilapia.

In this study, we determined the effect of a magnetic field applied during refrigeration in improving the quality of frozen tilapia. Alternating magnetic fields of 10 G, 20 G, 30 G, 40 G, and 50 G were applied during a low-temperature freezing treatment on the back, abdomen, and tail of tilapia. The control group was set at 0 G. A correlation analysis for the fish films after treating with different magnetic field strengths was carried out. The results showed that when the magnetic field was applied to assist freezing, the frozen quality of the tilapia was significantly improved, and the water separation and residual damage were reduced. The felled muscle tissue decreased, the fractal dimension value increased, the hardness decreased, and the elasticity increased. However, the impact of the magnetic field on the quality of the frozen tilapia did not change with an increase in the magnetic field strength. The effect on the back samples was more prominent when the fish were exposed to the magnetic field strength of 40 or 50 G. A magnetic field strength of 50 G was the most effective for the abdominal and tail samples. However, no significant difference was observed in the groups exposed to 10 and 20 G of magnetic fields.

EGCG-gelatin biofilm improved the protein degradation, flavor and micromolecule metabolites of tilapia fillets during chilled storage.

The protein degradation, flavor and micromolecule metabolites changes of (-)-epigallocatechin gallate (EGCG)-gelatin biofilm treatment (EGT) on chilled tilapia fillets in 21 days were investigated. Morphology observations revealed EGT protected good connective myofibrillar protein. It maintained protein secondary structure by significantly increasing the proportion of α-helix (15.20%) and decreasing the ratio of random coils (22.02%) in the EGT group compared to the control (CON) group (P < 0.05). Metabolomics with UHPLC-Q-TOF/MS analysis indicated a distinct separation between the CON and treatment groups at the end of storage. Small peptides analysis demonstrated that the EGT group increased the level of sweet peptides. Additionally, the EGT group significantly reduced the formation of amino acid derivatives and esters and off-flavor development. Overall, EGT effectively improved flavor, inhibited fish protein oxidation/degradation, and verified metabolomics results. This study unveiled the potential of metabolomics to analyze metabolites determined by tilapia and monitor the changes during storage.

Effect of vacuum frying and atmospheric frying on the quality and protein oxidation of squid (Loligo chinensis).

Squid are commercial marine species that have high nutritional value. This study aimed to compare the influences of vacuum frying and atmospheric frying on the physicochemical properties and protein oxidation of three main parts (ring, tentacle, and fin) of the squid Loligo chinensis. The results showed that the vacuum-fried (VF) group had lower moisture and total fat contents and looser microstructures than the atmospheric-fried (AF) group. The amino acid contents and molecular weight revealed that the proteins were well preserved during vacuum frying. Carbonyl content in the VF ring, tentacle, and fin samples increased nearly 2.53-, 1.54-, and 2.56-fold, respectively, compared to that in the corresponding fresh group, but these increases were lower than those of the corresponding AF group. In addition, the secondary structures of proteins revealed a slight decrease in the α-helix and ß-turn contents and a significant increase in the ß-sheet content during vacuum frying. Therefore, vacuum frying can be used as an efficient processing method to conserve the high nutritive quality of the product. PRACTICAL APPLICATION: As a developing alternative technology to prepare healthier fried products, vacuum frying has been the focus of recent researches. Vacuum frying produced squid products that had lower TBARS values, carbonyl contents, and Schiff base substances compared to atmospheric frying. And the protein secondary structures of the vacuum-fried group retained better. The study proved that vacuum frying could be an effective method with the advantages of high protein stability and product quality.

Sweet potato starch addition together with partial substitution of tilapia flesh effectively improved the golden pompano (Trachinotus blochii) surimi quality.

In order to improve the gel performance and edible quality of surimi for sustainable manufacture, the present study explored the feasibility of four kinds of starchs (potato, corn, sweet potato, and wheat) and fresh water fish tilapia as additives for golden pompano based surimi production. Sweet potato starch stood out as the most appropriate additive for golden pompano surimi due to the highest gel strength, lowest expressible moisture content and more compact microstructure. When the tilapia flesh substitution ratio reached 30%, best gel property of tilapia-golden pompano compound surimi with best texture property and whiteness value was achieved. Moreover, addition of 5% sweet potato starch to the golden pompano-tilapia (7:3) compound surimi comparatively obtained the optimal effect. Namely, it was observed that the texture parameters with hardness (3.62 N), gumminess (2.74 N), chewiness (17.35 mJ), cohesiveness (4.918), and springiness (0.872) being biggest values. On the other hand, the gel strength and expressible moisture content were 2,137.31 g. mm and 3.52%, respectively, which were overwhelming than other levels. Simultaneously, the whiteness of 5% addition group was 74.75, which was also a little higher than other groups. In summary, partial substitution of tilapia and proper addition of sweet potato starch effectively improved the gel performance and quality of golden pompano-based surimi products, which has potential applications in the industry of surimi.