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    Influence of non-thermal microwave radiation on emulsifying properties of sunflower protein
    (Elsevier Sci Ltd, 2022) Subasi, Busra Gultekin; Yildirim-Elikoglu, Seda; Altay, Ipek; Jafarpour, Ali; Casanova, Federico; Mohammadifar, Mohammad Amin; Capanoglu, Esra
    Sunflower protein isolate obtained from industrially de-oiled press cake was treated with non-thermal microwave, aiming to investigate how structure and emulsifying properties were affected. Our results indicated that the content of polar amino acids was decreased and solubility and surface hydrophobicity were altered upon exposure to non-thermal microwave. Higher solubility and surface hydrophobicity of the samples treated with defrost mode and also 350 W were accompanied by a smaller size and lower uniformity of the oil droplets compared to the control and other samples. Non-thermal microwave treatment improved the emulsion stability by 1.43 times and defrost mode treated sample had the lowest stability index after 120 min. Interfacial dilatational rheology measurements revealed that 70 and 350 W treated samples created higher elastic, less stretchable solid-like layer at the O/W interface in comparison with defrost mode treated and control samples. Consequently, non-thermal microwave treatment could be considered as a promising simple, fast, and green protein modification technique.
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    Non-thermal Approach for Electromagnetic Field Exposure to Unfold Heat-Resistant Sunflower Protein
    (Springer, 2023) Subasi, Busra Gultekin; Yildirim-Elikoglu, Seda; Altin, Ozan; Erdogdu, Ferruh; Mohammadifar, Mohammad Amin; Capanoglu, Esra
    The non-thermal effect of electromagnetic field (NEF) on the structural and thermal properties of heat-resistant globular sunflower protein isolate was investigated by exposing samples to varying power levels (70 W, defrost (DF), and 350 W). Only the lowest consecutive power modes of the electromagnetic unit were conducted to complete at least two exposure cycles (for certainty) without exceeding 45 degrees C (non-thermal processing condition). The total polar amino acid content of the treated samples decreased by 14% with NEF applications since polar amino acids were the main targets of the electromagnetic field due to absorbing that energy as kinetic energy and inducing structural changes. The DF and 350 W treatments dissipated large particles/aggregates over 5000 nm completely. The treatment with the lowest power (70 W) produced the lowest average particle size (14% decrease) while it increased after the DF and 350 W applications (34 and 16%, respectively), which indicated partial unfolding and/or reaggregation. Less ordered structures had increased alpha-helix (max with 350 W by 22%) and decreased beta-sheet contents (max with 70 W by 30%) after the NEF treatments. The tertiary structures of the samples changed significantly following the NEF treatments with a blue shift on emission maxima with different fluorescence intensities. The thermal stability of the samples was analyzed with DSC and TGA; lower peak temperature (decreased by 28%) and denaturation enthalpy (decreased by 82%) besides higher gravimetric loss (by 1.3%) were obtained for DF and 350 W, compared to the control. The NEF could be considered a promising approach for structural alteration of globular sunflower protein.