Atmospheric Cold Plasma Induced Modification of the Carob Germ Protein Isolate

Carob germ is a protein-rich industrial by-product derived from locust bean gum processing. This study evaluated the potential of atmospheric cold plasma (CP) as a physical modification strategy to improve the structural and techno-functional properties of the protein isolated from carob germ (CGP) over treatment durations of 5, 10, and 15 min. SDS-PAGE and FTIR analyses revealed that CP treatment preserved the subunit composition and main functional groups of CGP. However, deconvolution of the Amide I region demonstrated a shift from ordered β-sheets toward flexible random coils. 5-min CP exposure induced partial protein unfolding, which significantly increased surface hydrophobicity, free sulfhydryl content, and solubility. Simultaneous TGA/DSC analysis indicated that short-term CP treatment altered the thermal response of CGP, with the 5-min treatment showing the highest thermal decomposition rate, whereas the highest denaturation temperature and enthalpy were observed after 10 min. Techno-functional evaluations revealed that 5-min CP exposure produced the highest emulsifying activity index and a 2.1-fold increase in emulsion stability index. Extending CP treatment to 10 min maximized the foaming capacity, whereas prolonged 15-min exposure led to reduced solubility and emulsifying performance while maximizing water holding capacity. Overall, moderate CP treatment (5 min) serves as an effective, eco-friendly physical modification method to enhance the techno-functionality of CGP.