283: γ-Glutamylation of Ovalbumin Hydrolysates: Decreasing Bitterness and Retaining Bioactivity for Improved Glucose Uptake and Insulin Signaling in Rat Skeletal Muscle Cells L6

Introduction

Protein hydrolysates have garnered significant attention due to their potential health-promoting effects. However, their inherent bitterness presents a challenge to their incorporation into functional foods. Various methods have been proposed to reduce the bitterness of protein hydrolysates, but the main priority is to ensure that their bioactivity remains intact. γ-Glutamylation presents a novel enzymatic approach to address the bitterness issue by producing γ-glutamyl peptides known for their palatable taste and biological activity. This study investigates the application of γ-glutamylation to ovalbumin hydrolysates, which have previously demonstrated significant effects on glucose tolerance and insulin signaling In vivo, by exploring the impact of γ-glutamylation on both bitterness and bioactivity.

Methods

The γ-glutamylation process was conducted using Glutaminase from Bacillus amyloliquefaciens at pH 6, temperature 60°C, and enzyme /substrate ratio of 1%. The resulting hydrolysates following γ-glutamylation were characterized for their bitterness using an electronic tongue (SA402B) with the Bitter receptor C00, which demonstrated a statistically significant reduction in bitterness (P < 0.0001) compared to the hydrolysates prior to γ-glutamylation. Moreover, different alterations in chemical composition were observed following γ-glutamylation, including a decrease in the content of free glutamyl residues (P < 0.001) and the formation of different γ-glutamyl peptides, which are hypothesized to contribute to the reduction in bitterness. Furthermore, the effects of debittered ovalbumin hydrolysates on glucose uptake and insulin signaling pathways were investigated in stimulated insulin-resistant rat skeletal muscle cells (L6).

Results

The results demonstrated that debittered hydrolysates exhibited bioactivity comparable to bitter hydrolysates. This was indicated by a significant increase in glucose uptake (p < 0.0001) in L6 cells. Additionally, insulin-dependent signaling biomarkers were significantly enhanced, including the insulin-stimulated activation of protein kinase B (AKT), insulin receptor β (IRβ), and glucose transporter type 4 (GLUT4) (p < 0.0001).

Significance

These findings indicate that γ-glutamylation is a promising approach for reducing the bitterness of ovalbumin hydrolysates while maintaining their health-promoting properties, indicating their potential for functional food applications.

Authors: Nesma Elhadad, Jianping Wu