Soybean-based infant formulas (SBIFs) based on soybean protein isolate (90% of proteins) are an interesting alternative to cow's milk infant formulas. Different works have demonstrated the presence of bioactive peptides in different soybean-based foodstuffs. The aim of this work was the evaluation, for the first time, of antioxidant peptides in five different commercially available SBIFs. Ultrafiltration through 10 kDa molecular weight cut-off filters was the most suitable extraction method. Despite peptide concentrations ranging between 1.19 and 2.27 mg/mL, similar antioxidant capacities were detected in all SBIF extracts. Extracts were further fractionated according to their molecular weight by ultrafiltration, and fractions from 5 to10 kDa, 3 to 5 kDa, and below 3 kDa were obtained. The most active fraction was further fractionated by off-gel isoelectrofocusing and reversed-phase chromatography. Antioxidant fractions were also submitted to simulated gastrointestinal digestion (GI) with pepsin and pancreatin to evaluate their antioxidant capacity after digestion. Peptides were identified by HPLC-ESI-Q-ToF-MS/MS. At least 120 peptides were identified in every antioxidant fraction, with 42 peptides common to all SBIFs.
Bibliographical noteFunding Information:
Authors thank the Spanish Ministry of Science and Innovation (project CTQ2009-09022, and CTQ 2009-11252) and the Comunidad Autónoma of Madrid (Spain) and European funding from FEDER program (project S2009/AGR-1464, ANALISYC-II). Patrycja Puchalska thanks the University of Alcalá for her pre-doctoral contract.
- Antioxidant capacity
- Bioactive peptides
- Food analysis
- Soybean based infant formula