Influence of mono- and divalent cations on heat induced gelation of protein from mealworm (Tenebrio molitor) at various structural length scales

Mealworm protein gels are promising materials for food or medical applications. Our study aims to elucidate the influence of different salts (NaCl, MgCl 2 , and CaCl 2 ) on heat-induced gelation of mealworm protein at various structural length scales. Results from rheology, UV-vis and turbidity in fluorescence spectroscopy show an overall increase in aggregation and rheological moduli with addition of ions in the order “no salt” < NaCl < MgCl 2 < CaCl 2 . Prior to heating, this increase is accompanied by an increase of the scattering exponent for Q <0.01 from SAXS if divalent cations are added, indicating the formation of more compact aggregate structures. Based on results from FT-IR, this can be related to an increase in inter- and intramolecular hydrogen bonding but no specific coordination of the divalent cations with carboxylic groups from the protein side chains can be shown. From scaling of rheological parameters, these additional interactions are derived to occur mainly within the initial flocs rather than between them during the formation of a room spanning gel. Scattering exponents indicate a transition from mass fractals to surface fractals for gels without added salts and gels with NaCl and MgCl 2 , while the gel structure of gels with added CaCl 2 consisted of mass fractals. • Combination of spectroscopy, SAXS and rheology for gel structure characterisation • Mealworm protein forms heat induced gels with and without NaCl, MgCl 2 or CaCl 2 • Divalent cations lead to denser protein aggregates with larger fractal dimensions • Gelation causes transition from mass- to surface fractals unless CaCl 2 is added • Divalent cations increase the contribution of intrafloc interactions after gelation