Functional Properties of Water-soluble Proteins from Silver Carp (Hypophthalmichthys molitrix) Conjugated with Five Different Kinds of Sugar

Characterization of silver carp myosin glycated with phosphorylated konjac oligo-glucomannan

BACKGROUND

Myosin (Ms) is abundant in fish meat, but it has limited application in the food industry because of its low solubility and thermal stability. Our previous reports found that these functional properties of Ms can be significantly improved after glycation with konjac oligo-glucomannan (KOG). However, the effects of phosphorylated KOG (PKOG) on physicochemical, structural and functional properties of silver carp Ms are still unknown.

RESULTS

This study characterized the silver carp Ms protein glycated with PKOG at 50 °C and 75% relative humidity for 48 h. As degree of phosphorylation increased, free amino content increased, whereas degree of grafting decreased. Meanwhile, isoelectric point (pI) reduced, however, PKOGs showed no differences in pI. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis suggested the formation of glycoconjugates, and scanning electron microscopy revealed thinner flakes and uneven appearance of glycoconjugates. Fourier transform infrared spectroscopy indicated that the amide I, II and III bands of Ms were changed by the glycation. Ms became highly soluble in 0.5 mol L^-1 NaCl with increased phosphate addition in PKOGs. Thermal stability of Ms was effectively improved when heated at 80 °C for 60 min.

CONCLUSION

Glycation with appropriate PKOG might be a promising method for Ms modification because of the resulting improvement in solubility and thermal stability. © 2021 Society of Chemical Industry.

Comparison of quality and nutritional attributes of pond-cultured and container-cultured snakehead (Channa argus argus) fillets after being boiled, fried, and baked

The objective of this study was to compare the quality and nutritional attributes of snakehead (Channa argus argus) fillets (cultured in ponds and containers) after being heated (boiling, frying, and baking). The results revealed that there were few differences in quality (flavor, color, and texture) and nutritional attributes (content of amino acid, dipeptidyl peptidase IV (DPP-IV) and angiotensin I-converting enzyme (ACE) inhibition activity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity) of snakehead fillets obtained from two cultured modes. Container-cultured samples exhibited more beneficial effects on flavor (more esters) and bioactivity (ACE inhibition and DPPH scavenging activity) than pond-cultured. Frying increased flavor attributes but decreased nutritional value of fish. Boiling was an effective heating method for increasing quality and nutritional attributes of container-cultured snakehead fish. Generally, the container-cultured mode was applicable for culturing snakehead without decreasing quality and nutritional attributes, which deserved more attention. PRACTICAL APPLICATION: The study provided information about the differences of quality properties (flavor and texture) and nutritional attributes (bioactive functions of simulate-digested products) of pond-cultured and container-cultured snakehead fish after being heated. The results will provide some potential values for the application of container-cultured technology.

Physicochemical Properties of Bovine Serum Albumin-Glucose and Bovine Serum Albumin-Mannose Conjugates Prepared by Pulsed Electric Fields Treatment

The pulsed electric fields (PEF) treatment is a novel method for obtaining glycated proteins by way of a Maillard reaction between proteins and polysaccharides but its effect on the preparation of protein–monosaccharide conjugate has not been explored. This study aimed to prepare bovine serum albumin (BSA)–glucose and BSA–mannose conjugates using PEF in pH 10.0 at an intensity of 10 or 20 kV/cm, frequency of 1 kHz, pulse width of 20 μs and 73.5 pulses. The conjugates were evaluated for physicochemical properties. The results indicated that PEF not only promoted Maillard reaction between BSA and glucose or mannose but also alleviated the undesirable browning. PEF treatment favored the increased surface hydrophobicity and emulsifying activity in BSA but reduced surface hydrophobicity and foaming stability and improved foaming capacity in BSA–glucose and BSA–mannose conjugates. These findings provided useful considerations in the application of PEF treatment as a potential method to prepare BSA–monosaccharide conjugates by Maillard reaction.

Quality Changes and Biogenic Amines Accumulation of Black Carp (Mylopharyngodon piceus) Fillets Stored at Different Temperatures

Postmortem quality changes of black carp (Mylopharyngodon piceus) fillets stored at 20, 4, and 0°C (in ice) were determined in terms of pH value, K value, total volatile basic nitrogen, free amino acids, biogenic amines, drip loss, electrical conductivity (EC), sensory score, and microbial growth. The results showed that black carp fillets could maintain a good quality for 2, 9, and 12 days when stored at 20, 4, and 0°C, respectively. Pseudomonads, Aeromonas, and Enterobacteriaceae were the main spoilage bacteria in black carp. Tryptamine, 2-phenylethylamine, putrescine, cadaverine, and tyramine increased significantly (P < 0.05) during storage at the three temperatures, but not spermidine and spermine, among which tyramine and putrescine were the main biogenic amines in black carp fillets. A significantly higher concentration of histamine (132.05 mg/kg on the third day) was detected in the samples stored at 20°C (P < 0.01) than at 4 and 0°C (0.62 to 3.28 mg/kg) throughout storage, indicating storage of samples at 20°C favored the formation of histamine. The accumulations of tyramine, cadaverine, and histamine were highly correlated with the productions of tyrosine, lysine, and histidine, respectively. Correlations between EC and sensory, physical, chemical, and microbial parameters at the three storage temperatures showed that EC could be used as a better quality indicator to assess the overall quality of fish stored at 4 and 0°C (low temperature) than at 20°C.