Effects of NaCl on water characteristics of heat-induced gels made from chicken breast proteins treated by isoelectric solubilization/precipitation

Effect of ultrasonic thawing on the water-holding capacity, physicochemical properties and structure of frozen tuna (Thunnus tonggol) myofibrillar proteins

BACKGROUND

The effect of ultrasonic thawing (0, 160, 280, 400 W) on water-holding capacity (WHC), physicochemical properties and structure of tuna myofibrillar proteins was investigated.

RESULTS

Thawing time was shown to decrease and thawing loss to increase significantly (P < 0.05) as power increased (160-400 W), whereas there was no significant difference (P > 0.05) in cooking loss. Changes in T₂ relaxation time were investigated using low-field nuclear magnetic resonance. Ultrasonic thawing could significantly (P < 0.05) improve the immobilised water content compared to the control (0 W). surface hydrophobicity decreased significantly and then increased significantly (P < 0.05), whereas there was no significant difference (P > 0.05) in the reactive sulfhydryl content as power was increased. Tuna thawed at 280 W suffered fewer negative effects on its microstructure. Roman spectral date showed that the α-helix changed to a random coil and β-turn as power was increased (up to 400 W).

CONCLUSION

The application of ultrasonic thawing at a specified power was showed to be a beneficial process when used in the seafood industry, but application of excessive power resulted in lower WHC and structural changes to myofibrillar proteins. © 2019 Society of Chemical Industry.

Rapid and Non-Destructive Detection of Water-Injected Pork Using Low-Field Nuclear Magnetic Resonance (LF-NMR) and Magnetic Resonance Imaging (MRI)

The challenges of food adulteration such as illegal production of water-injected meat remain serious in many areas of the world. This study investigated the feasibility of using LF-NMR and MRI to identify water-injected pork. Longissimus dorsi muscles were injected with 0 %, 5 %, 10 %, 15 %, 20 % and 25 % content of deionized water, respectively. The CPMG decay curves of water-injected pork decayed slower than that of the normal. The peak area proportion of immobilized water of water-injected pork decreased while relaxation time and peak area proportion of free water increased significantly (p < 0.05). The first two principal components (PCs) of PCA accounted for 54.54 % and 32.06 % of the observed variance, respectively. Based on the two PCs, the water-injected pork could be differentiated from the normal. Furthermore, the accumulation location of the injected-water in pork could be visualized by MRI. Therefore, LF-NMR combined with MRI offers an effective method for the detection of water-injected pork.

Sustained Swimming Training Is Associated With Reversible Filet Texture Changes of European Sea Bass (Dicentrarchus labrax L.)

This present study aimed to investigate the effect of training and detraining on the growth, chemical composition, white muscle fibers, and filet texture of the European sea bass (Dicentrarchus labrax L.). Fish were divided into control and training groups, which were subjected to water velocities of 0.2 and 1.0 body length per second (bl s-1), respectively, for 32 days (phase I). Half of the fish in the training group were then randomly selected and detrained at a velocity of 0.2 bl s-1 for another 32 days (detraining group), while the velocity of the remaining fish in the training group (1 bl s-1), and control group (0.2 bl s-1) remained unchanged (phase II). The results showed that the growth, body composition, and white muscle fiber densities of the control and trained fish were not significantly different in either phase. Training significantly altered the muscle fiber distribution (P < 0.05), with the training group having fewer 80-90 μm fibers than the control and detraining group at the end of the experiment (P < 0.05). The training group also had significantly higher values for white fiber muscle textural parameters (hardness, adhesiveness, cohesiveness, springiness, gumminess, and chewiness) in phase I (P < 0.05), and these parameters correlated significantly with pH (P < 0.05). However, these differences in texture and the pH correlation weakened when the fish were detrained in phase II. These results indicated that an increase in muscle pH after training may alter the flesh texture characteristics of sea bass. In addition, sustained swimming could induce a reversible change in the filet texture of sea bass.

Effects of Drying Methods and Ash Contents on Heat-Induced Gelation of Porcine Plasma Protein Powder

Porcine blood plasma is a rich source of proteins with high nutritional and functional properties, which can be used as a food ingredient. The plasma is usually processed into powders in applications. In the present study, the effects of drying methods and ash contents on heat-induced gelation of plasma protein powder were investigated. The drying methods had a significant impact on the gel properties of the plasma powder heat-induced gels. The hardness and elasticity of the gels by freeze-dried and spray-dried plasma powders were lower than that of the liquid plasma (p < 0.05). The microstructures of dehydrated plasma were denser and the holes were smaller. The secondary structure of the gels from the spray-dried plasma protein powders exhibited more α-helixes and less β-turns than that from the freeze-dried powder and liquid plasma. The thermostability of dehydrated plasma powder was found to have decreased compared to the liquid plasma. Compared with the gels obtained from the high ash content plasma protein powders, the gel from the 6% ash content plasma powder had the highest water-holding capacity and had the lowest hardness and elasticity. However, the secondary structure and microstructures of the heat-induced gels were not affected by the ash contents in the plasma powders. These findings show that the gel properties of plasma protein powder can be finely affected by drying methods and ash contents.