Cold Atmospheric Plasma-Induced Modifications in the Structural and Techno-Functional Properties of Pequi Almond (Caryocar brasiliense Camb.) Proteins

Abstract

This study investigated the effects of cold atmospheric plasma (CAP) treatment (2–10 min) on the structural properties and functional performance of pequi almond protein (PAP). Structural changes were evaluated through spectroscopic and chemical analyses, including free sulfhydryl and carbonyl contents, as well as secondary and tertiary structural modifications. Techno-functional properties related to solubility, emulsification, water- and oil-holding capacities, and rheological behavior were also assessed. Short CAP exposure (2–4 min) improved PAP functionality. Solubility increased up to ~ 2.6-fold, the emulsifying activity increased nearly sevenfold after 2 min, emulsifying stability improved by ~ 2.7-fold, and water- and oil-holding capacities increased by ~ 2.0-fold. These improvements were associated with conformational rearrangements at secondary and tertiary structural levels, evidenced by increased fluorescence intensity, UV–Vis absorbance, changes in FTIR profiles, and enhanced surface hydrophobicity (~ 2.31-fold), indicating partial protein unfolding and improved interfacial activity. FTIR analysis confirmed time-dependent rearrangements in the secondary structure of PAP, with β-sheet content increasing from 46.07% to 51.06%, while α-helix content remained relatively stable (22.19–21.97%) and β-turn content decreased from 26.53% to 22.64%. CAP treatment also altered the colloidal and rheological behavior of PAP dispersions. At prolonged exposure, apparent viscosity at 50 s⁻¹ increased from 2.0 ± 0.2 to 9.6 ± 0.1 mPa·s, accompanied by increases in particle size, polydispersity index, and rheological parameters, suggesting protein aggregation and network formation. These effects were accompanied by increased carbonyl content and reduced free sulfhydryl groups, indicating oxidative modifications induced by prolonged plasma exposure. Overall, CAP represents a promising strategy for tailoring PAP functionality under the processing conditions evaluated. These findings highlight the importance of controlling plasma exposure time to balance structural modification, oxidative reactions, and functional performance, and provide a basis for further evaluating CAP-treated PAP in food-relevant formulations.