Preparation, characterization, and bioavailability evaluation of antioxidant phosvitin peptide-ferrous complex.

BACKGROUND: Iron deficiency anemia (IDA) is one of the commonest global nutritional deficiency diseases, and the low bioavailability of iron is a key contributing factor. The peptide-iron complex could be used as a novel iron supplement to improve iron bioavailability. RESULTS: In this study, antioxidant low molecular weight (<3 kDa) phosvitin peptide (named PP-4) was separated to prepare a phosvitin peptide-ferrous complex (named PP-4-Fe); then the structural conformation of PP-4-Fe was characterized and its bioavailability by in vitro digestion was evaluated. The results showed that PP-4 had good ferrous-binding activity with 96.14 ± 2.86 µg Fe2+ mg-1 , and had a strong antioxidant effect with 995.61 ± 79.75 µmol TE mg-1 in 2,2'-azinobis'3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 62.3 ± 3.95 µmol FeSO4 mg-1 in ferric ion reducing antioxidant power (FRAP). After ferrous binding, the FRAP activity of PP-4-Fe, enhanced by 1.8 times, formed a more ordered structure with an increase in α-helix and decrease in γ-random coil. The ferrous binding sites of PP-4 involved were the amino, carboxyl, imidazole, and phosphate groups. The PP-4-Fe complex displayed excellent gastrointestinal stability and antioxidant effects during digestion. The iron dialysis percentage of PP-4-Fe was 74.59% ± 0.68%, and increased to 81.10% ± 0.89% with the addition of 0.25 times vitamin C (VC). This indicated that PP-4-Fe displayed excellent bioavailability and VC in sufficient quantities had a synergistic effect on improving bioavailability. CONCLUSIONS: This study demonstrated that antioxidant phosvitin peptide was an efficient delivery system to protect ferrous ions and suggested that the phosvitin peptide-ferrous complex has strong potential as a ferrous supplement. © 2023 Society of Chemical Industry.

Combined treatment of lactic acid-ultrasound-papain on yak meat and its tenderization mechanism.

The combined effects of lactic acid-ultrasound-papain on yak meat tenderization were investigated, and its tenderization mechanism elucidated. The optimal condition for combined tenderization was obtained with 0.03% lactic acid, ultrasound for 30 mins, and 200 U/g of papain. When compared with the untreated yak meat, the cutting force and the cooking loss of the tenderized yak meat were decreased by 62.16% and 31.25%, respectively, while the myofibrillar fragmentation index increasing 4.3 times. After the combined tenderization, it was observed a loose arrangement of muscle with larger gaps and cavities. The random-coil content of myofibrillar protein increased to 48.3%, while α-helix decreased to 14.4%, indicating that the myofibrillar protein underwent some unfolding and stretching. These results demonstrated that this combined treatment improved the tenderization of yak meat by disrupting muscle integrity, increasing its water-holding capacity, denaturing myofibrillar protein, and changing its spatial structure. The combined process using lactic acid-ultrasound-papain showed some potential to improve meat texture.

Binding mechanism and bioavailability of a novel phosvitin phosphopeptide (Glu-Asp-Asp-pSer-pSer) calcium complex.

Phosvitin has excellent calcium binding capacity, related to its phosphopeptides. The phosphopeptides may be used as functional ingredients for improving calcium bioavailability, but the calcium-binding mechanism is unclear. In this study, a novel phosvitin phosphorylated pentapeptide (Glu-Asp-Asp-pSer-pSer, EDDpSpS) was selected to prepare an EDDpSpS calcium complex (EDDpSpS-Ca), and the calcium-binding mechanism and bioavailability investigated. The calcium-binding capacity of EDDpSpS was up to 468 ± 152.80 mg/g. Calcium ions prompted the folding of the EDDpSpS structure to form spherical nanoparticles. The calcium binding sites of EDDpSpS involved peptide bonds, carboxyl, amino, and phosphate groups. Molecular forces involved in these interactions were electrostatic in nature. Moreover, EDDpSpS-Ca had excellent bioavailability when compared to CaCO3, calcium lactate, and d-calcium gluconate. This study revealed the calcium-binding mechanism of phosvitin phosphopeptide, and suggested that EDDpSpS-Ca has the potential to be a novel, efficient, and promising calcium supplement.