Effect of pH and Heat Treatment on the Antioxidant Activity of Egg White Protein-Derived Peptides after Simulated In-Vitro Gastrointestinal Digestion

Abstract

The study aimed to analyze pH and heat treatment’s effect in modulating the release of peptides with antioxidant activity after simulated gastrointestinal (GI) digestion of Egg white powder (EWP). EWP samples with neutral (EWPN) and alkaline (EWPA) pH were heat-treated at 20, 60, and 90 °C and analyzed for protein aggregation, solubility, and GI digestibility. Heat treatment decreased solubility and induced protein aggregation, which was higher for EWPN as compared to EWPA. The unfolding of EWPA proteins at 60 °C exhibited a higher GI digestibility and antioxidant activity via Oxygen Radical Absorbance Capacity (ORAC) assay as compared to EWPN. Interestingly, a reverse trend was observed in the cellular antioxidant assay, and the GI-digest of EWPN exhibited a higher antioxidant activity. The LC-MS/MS analysis are in concordance with cellular antioxidant activity assay and showed a higher intensity for peptides with potential antioxidant activity in the GI-digest of EWPN. The results indicate that heat treatment but not the pH is a critical factor in improving the protein digestibility and releasing peptides with antioxidant activity after GI digestion.

Bioactivity of Cooked Standard and Enriched Whole Eggs from White Leghorn and Rhode Island Red in Exhibiting In-Vitro Antioxidant and ACE-Inhibitory Effects

“…Similarly, ACE-inhibition with the whole hydrolysate tended to be better in RIR boiled samples compared to boiled, although no significant difference was observed and the tendency did not hold for WLH samples. Following previous studies, we found a discrepancy between chemical and cell-based antioxidant capacity [35,36]. Caution should be taken when interpreting the physiological relevance of whole egg hydrolysates chemical antioxidant capacity, which depends on inherent pathways and metabolism of the cells in question.…”

“…The difference between chemical and cellular antioxidant activity can be observed in the CAA assay, where the samples with the highest antioxidant activity in the ORAC assay were unable to reduce the ROS production compared to quercetin, a radical quencher phytochemical [27]. Rao et al, in 2020, suggested that high molecular weight peptides from egg white can potentially exhibit a higher antioxidant activity in ORAC due to their radical quenching capacity independently of their bioavailability [35]. In a physiologically relevant model, the peptides need to be absorbed by the cell to confer their antioxidant activity and quench the intracellular ROS measured in the CAA assay [27].…”

“…Previous studies have confirmed the different antioxidant capacity of bioactive compounds, such as peptides from chemical assays compared to in vitro cell models [35,36]. The CAA model is based on the quenching of peroxyl radicals generated by AAPH [27].…”

Effect of thermal treatment on the antioxidant activity of egg white hydrolysate and the preparation of novel antioxidant peptides

“…According to Rao et al . (2020), the heat treatment at 65 ℃ for 30 min might enhance the release of peptides with potential antioxidant activity. In addition, small peptides (MW < 3 kDa) can form secondary structures, which are the key factors affecting the antioxidant activity of peptides (Zhu et al ., 2014).…”

In-vitro digestion models: a critical review for human and fish and a protocol for in-vitro digestion in fish

“…In particular, static digestion model is widely used to evaluate the effect of food processing on the nutrient bioaccessibility (nutrient released from the food matrix), bioavailability (including nutrient absorption), or allergenic peptides. Several food processing techniques, such as heat-treatment [27][28][29][30], drying [31], curing/aging [32], ultrasonication [33,34], and protein extraction [35], have been employed for numerous food products.…”