Textural quality and oxidative stability of restructured pangasius mince: effect of protein substrates mediated by transglutaminase

Development of Yellow Discoloration in Sawai (Pangasianodon hypophthalmus) Muscle due to Lipid Oxidation

In this study, we investigated the impact of lipid oxidation on the discoloration of Sawai (Pangasianodon hypophthalmus) lipids and proteins. Sawai microsomes, liposomes, and salt-soluble myofibrillar proteins were prepared and subjected to lipid oxidation process. The results revealed that the levels of thiobarbituric acid-reactive substances, yellowness (as indicated by b* values), and pyrrole compounds increased when Sawai liposomes and microsomes were oxidized using iron and ascorbate. Meanwhile, the levels of free amines decreased, particularly as the iron content (25∼100 μM) and incubation time (0∼20 h) increased. The impact of oxidized liposomes at different levels (1, 2, and 5%) on the salt-soluble Sawai myofibrillar proteins was also evaluated. The findings revealed that lipid oxidation products reduced the sulfhydryl content and increased the surface hydrophobicity and carbonyl content of the salt-soluble Sawai myofibrillar proteins. These results imply that the formation of yellow discoloration in Sawai muscle could be due to nonenzymatic browning reactions occurring between lipid oxidation products and amines in the muscle protein.

Effect of citric acid on physicochemical properties and protein structure of low-salt restructured tilapia (Oreochromis mossambicus) meat products

BACKGROUND

The growing consumer demand for healthy products has encouraged the development of low-salt meat products. In this study, to develop low-salt restructured tilapia (Oreochromis mossambicus) meat products, citric acid was used to improve the properties of restructured tilapia products.

RESULTS

In comparison with control restructured fish products (RP) and surimi products (SP), 0.2% citric acid-treated restructured fish products (RPC) and surimi products (SPC) showed a significant decrease in expressible water and water activity and a remarkable increase in whiteness, dry matter, hardness, chewiness, gumminess, and acceptability. Mechanistic studies suggested that citric acid significantly changed the content of total protein and myofibrillar proteins and promoted degradation of heavy myosin chains. Fourier-transform infrared and Raman spectra revealed the citric acid-mediated alteration in the peak intensities of amide I and amide II bands, which changed the secondary structures of RPC and SPC.

CONCLUSION

It is feasible to prepare low-salt restructured tilapia meat products using citric acid, which offers a means of using muscle by-products and exploiting new functional products with an added commercial value. © 2020 Society of Chemical Industry.

Quality Changes and Discoloration of Basa (Pangasius bocourti) Fillet during Frozen Storage

Physicochemical changes of Basa fish (Pangasius bocourti) fillet during frozen storage at −20°C for 0–20 weeks were studied. The content of thiobarbituric acid reactive substances (TBARS) of fish samples suddenly increased when the samples were stored longer than 8 weeks (p<0.05). The increase in TBARS value of the fish fillet was concomitant with the increase in b∗ value (yellow color). Marked decreases in Ca2+-ATPase activity, sulfhydryl content, and protein solubility of the fish fillet after 8 weeks of storage were observed. Those decreasing values were well correlated with the increasing of disulfide bond content and surface hydrophobicity content (p<0.05). Increases in shear force of fish meat during storage were also observed (p<0.05). The results indicated that frozen storage at −20°C affected on Basa fillet qualities, especially after 8 weeks of storage. These data could be useful for consumer and food industry.

Current and future prospects for the use of pulsed electric field in the meat industry

Pulsed electric field (PEF) is a novel non-thermal technology that has recently attracted the attention of meat scientists and technologists due to its ability to modify membrane structure and enhance mass transfer. Several studies have confirmed the potential of pulsed electric field for improving meat tenderness in both pre-rigor and post-rigor muscles during aging. However, there is a high degree of variability between studies and the underlying mechanisms are not clearly understood. While some studies have suggested physical disruption as the main cause of PEF induced tenderness, enzymatic nature of the tenderization seems to be the most plausible mechanism. Several studies have suggested the potential of PEF to mediate the tenderization process due to its membrane altering properties causing early release of calcium ions and early activation of the calpain proteases. However, experimental research is yet to confirm this postulation. Recent studies have also reported increased post-mortem proteolysis in PEF treated muscles during aging. PEF has also been reported to accelerate curing, enhance drying and reduce the numbers of both pathogens and spoilage organisms in meat, although that demands intense processing conditions. While tenderization, meat safety and accelerated curing appears to be the areas where PEF could provide attractive options in meat processing, further research is required before the application of PEF becomes a commercial reality in the meat industry. It needs to deal with carcasses which vary biochemically and in composition (muscle, fat, and bones). This review critically evaluates the published reports on the topic with the aim of reaching a clear understanding of the possible applications of PEF in the meat sector in addition to providing some insight on critical issues that need to be addressed for the technology to be a practical option for the meat industry.

Effects of l-lysine on thermal gelation properties of chicken breast actomyosin

The effects of l-lysine (l-Lys) on the water holding capacity (WHC) and texture of actomyosin (AM) gel and the possible mechanisms were investigated. l-Lys increased the WHC and hardness of the AM gel. These effects may be related to the even and continuous microstructure of the gel according to the scanning electron microscopy analysis. Furthermore, l-Lys increased the surface hydrophobic residues and the reactive sulfhydryl groups. l-Lys decreased the storage modulus at the first transition temperature but increased it at the second transition temperature and the third transition enthalpy. These results suggested that l-Lys varied the thermal behaviors and the microstructure of the AM gel by increasing the surface hydrophobicity and reactive sulfhydryl groups, ultimately contributing to the increased WHC and hardness. The changes in pH did not fully explain the results from the present study. The results were useful for understanding previous findings and may serve as a reference for the preparation of reduced-sodium and phosphate-free meat products.

Effect of chitosan on shelf life of restructured fish products from pangasius (pangasianodon hypophthalmus) surimi during chilled storage

In the present study, restructured products were prepared from pangasius surimi and their qualities were analysed under chilled storage. Pangasius surimi had 75.82 % moisture, 16.91 % protein, 2.76 % fat and 0.95 % ash. Restructured products were prepared in three different formulations by incorporating corn starch (10 %) and chitosan (0.75 %). Formulation containing only corn starch (10 %) was served as control. In all the formulations, mono unsaturated fatty acids were higher (45.14 %). The total volatile base nitrogen (TVB-N) showed an increasing trend and it was found to be higher in control (4.8 mg/100 g) on 10(th) day than the chitosan incorporated sample (3.5-4.2 mg/100 g) on 17(th) day during chill storage. Similarly, peroxide value (PV) was found to higher (8.85 milliequivalent of O2/kg) in control than the chitosan incorporated sample (4.5-6.8 milliequivalent of O2/kg) on 10(th) day. All the three formulations had an acceptable level of thiobarbituric acid (TBA) value that ranged between 0.023-0.098 mg of malanoldehyde/kg during chilled storage. Based on the sensory and microbiological analysis, products prepared without chitosan had a shelf life of 10 day whereas, products incorporated with chitosan had an extended shelf life of 17 day.