Edible insect protein concentrates: Optimized salt-assisted extraction methods evaluation

Abstract

This study explores the extraction of proteins from edible insects such as Tenebrio molitor, Acheta domesticus, and Locusta migratoria using alkaline extraction and acid precipitation (AEAP) as a control method and evaluates the influence of salting-in (NaCl-assisted), salting-out ((NH₄)₂SO₄), and combined salting-in/out techniques on the resulting protein quality and functional properties. We hypothesized that salt-assisted methods would enhance protein extraction efficiency and functionality compared to AEAP. Molecular size distribution analysis confirmed that the salting-out method preferentially aggregated smaller proteins (<30 kDa). FT-IR spectroscopy revealed notable changes in protein secondary structure across extraction methods, while amino acid profiling identified 17 amino acids, with essential amino acids (EAAs) comprising 37.8–44.2 % of total amino acids. Salt-assisted methods significantly increased the zeta potential (up to −62.67 mV) and modulated particle size distribution (180–492 nm) compared to the control samples. Rheological properties varied with extraction techniques, with potential fluid-type transitions. Proteins extracted via salt-assisted methods demonstrated high purity (>70 %), enhanced solubility (>60 % at pH 7.4), improved oil- and water-holding capacities (1.40–8.09 g/g, 2.41–4.4 g/g), and superior emulsifying properties (EAI >47 m2 g−1, ESI >50 %). These findings highlight that salt-assisted extraction methods can improve the quality and functionality of insect protein concentrates, supporting their potential for food-grade applications.