Improvement of techno-functional properties of acidic subunit from amaranth 11S globulin modified by bioactive peptide insertions

Abstract

Background: Proteins are often used in foods as ingredients to provide desirable appearance, texture, or stability. It is commonly used as gelling, emulsifiers, foaming, and thickeners. An awareness of its properties can be achieved by exploring the relationship between structural conformation adopted by a protein and its techno-functional properties. Here, we analyzed the techno-functional properties of the acidic subunit from amarantin AAC and modified variants AACM.1 and AACM.3 with bioactive peptides (VY 4x) insertion. The proteins were expressed at the fermenter level using Escherichia coli. The techno-functional properties were analyzed at different pH and compared with fresh white egg and sodium caseinate. Moreover, the structural characterization of proteins was done through infrared and Raman spectroscopies.

Results: The techno-functional properties of all proteins studied were better at pH 7.5. Solubility and emulsifying activity of AAC and AACM.3 were similar to sodium caseinate, at pH 5. AACM.3 showed similar foaming stability to the white egg, while at pH 7.5, both modified proteins showed higher foaming stability and were equivalent to the white egg. Spectroscopic techniques showed conformational differences between AAC and modified variants. AACM.3 showed higher unordered secondary content (59.6%) followed by AACM.1 (39.6%), suggesting AACM.3 adopted a structure as a molten globule by modifications done, which enhance its techno-functional properties.

Conclusions: The biopeptide insertions promote conformational changes, such as structure molten globule (AACM.3) and compact structure (AACM.1). In both cases, the techno-functional properties were improved, it could be an advantage focusing on plant protein ingredient development to novel food product creation.