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Thermally Stimulated Luminescence in Powdered Soy Proteins
Author(s) -
Abdi Dereje,
Jahan Muhammad S.,
Boatright William L.,
Walters Benjamin M.,
Lei Qingxin
Publication year - 2014
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/1750-3841.12325
Subject(s) - luminescence , electron paramagnetic resonance , analytical chemistry (journal) , chemistry , soy protein , fraction (chemistry) , nuclear chemistry , materials science , chromatography , nuclear magnetic resonance , food science , physics , optoelectronics
Heating powder isolated soy proteins (ISPs) in a N 2 environment produced thermally stimulated luminescence (TSL), in 2 major temperature regions, 50 to 250°C (region R1) and 250 to 350°C (region R2). In soy protein 7S fraction, strong TSL was detected in both regions with glow peak maximum ( T m ) at 150 ± 15°C and at 300 ± 10°C. Two additional satellite or shoulder peaks were detected from the ISP and 7S protein fraction within region R1 at T m = 90°C and T m = 210°C. The soy protein 11S fraction produced a broad, poorly defined TSL peak in the low‐temperature region. Electron paramagnetic resonance spectroscopy data from the control ISP sample, deuterium sulfide‐treated ISP, ISP stored in either N 2 or O 2 , and defatted soy flour, indicated that the trapped radicals present in ISP is associated with the production of the primary TSL peak at 150 ± 15°C. Activation energies required to release the trapped charges (for luminescence to occur) are approximately 0.70, 0.78, 1.50, and 1.8 eV for TSL at T m = 100, 150, 200, and 300°C, respectively. The reaction mechanism that leads to the release of the trapped charges for TSL to occur followed a mixed order kinetic, between 1.5 and 1.8. The frequency factor varied between 10 7 /s and 10 17 /s.