Antioxidant Hydrolysate of Sericin from Bombyx mori Cocoons

Synthesis and Characterisation of Chickpea Peptides-Zinc Chelates Having ACE2 Inhibitory Activity

Tryptic hydrolysates of protein fractions obtained by the Osborne method from chickpea (Cicer arietinum L.) seeds interacted with zinc ions and the results of chelation were monitored by the Energy Dispersive X-Ray (EDX) technique. The glutelin hydrolysate (GluHyd) reacted with zinc ions and depicted a relatively higher zinc content. For this reason, the zinc complex of the glutelin hydrolysate (GluHyd-Zn) was studied deeper, and 11 peptides were identified in its more zinc-containing second fraction obtained after gel filtration. The peptide HKERVQLHIIPTAVGK showed a relatively higher chelating capacity (57.86 ± 2.14%). According to the result of the ICP-OS analysis, 1 mg peptide could chelate 381.61 ± 133.39 µg zinc, and the molar ratio of peptide-zinc was about 1:4. Spectral methods proved that side chain and C-termini carboxyl groups of the peptide mostly were involved in chelation and N atoms of amino side chains, imidazole group of histidine, and N-termini at some extents were occupied by the metal ions. Modeling of zinc-peptide interaction was done using Molecular Operating Environment (MOE) software. The results of the docking correlate with the experimental data.ACE2 inhibitory effect of HKERVQLHIIPTAVGK-Zn complex (IC50 = 1.5 mg/mL) was better than that of HKERVQLHIIPTAVGK (IC50 = 2.2 mg/mL).

Anti-hardening effect and mechanism of silkworm sericin peptide in high protein nutrition bars during early storage

Hardening presents an inevitable challenge during the storage of high protein nutrition bars. Sericin peptide is the product of hydrolysis of sericin, a protein from the silkworm cocoon. Here in, the effects of sericin peptide addition on the hardening of high protein nutrition bars during 72 h of storage were investigated. The addition of sericin peptide to high protein nutrition bars reduced the hardening of the sample during the early storage, The main mechanism was to improve the mobility of water and small hydrophilic molecules, which slowed down the phase separation. As well, after sericin peptide addition, the ζ- potential, the content of secondary structure, and the surface hydrophobicity of the samples were also changed, which prevented the self-aggregation of proteins. These results indicate that SRP can be used as a promising anti-hardening ingredient in the food industry to improve the texture of food products.

Factors affecting sericin hydrolysis and application of sericin hydrolysate in sericin films

Sericin is a natural protein and a by-product obtained from silk processing. To enhance the antioxidant properties of sericin, sericin hydrolysis was studied. The solvent effects (distilled water, citric acid and hydrochloric acid) and hydrolysis methods (heat treatment (water bath) and mild ultrasonic treatment at 20%, 40% or 60% amplitude) were investigated on the properties of sericin hydrolysate (SH). Furthermore, solvent effects (distilled water and 15% ethanol) were examined for the properties of the sericin films incorporated with selected SH. The SH samples from acid hydrolysis and the ultrasonic method had a darkened visual appearance. However, the degree of hydrolysis and antioxidant activity of SH increased with ultrasonic-assisted acid hydrolysis. The molecular weight (MW) of sericin was notably reduced. As expected, hydrochloric acid hydrolysis resulted in a lower MW for the SH than from citric acid. Thus, SH from hydrochloric acid and 20% amplitude in the ultrasonic method were selected to produce a sericin film. As revealed, using distilled water as a general solvent provided films with lower solubility and water vapor permeability but higher tensile strength. Furthermore, the addition of SH enhanced the antioxidant properties of its hydrolysate as a novel protein packaging film material for various applications.