PSXIII-5 - Using Synchrotron-radiation based Microspectroscopy to detect the effects of steam pressure toasting duration on protein-related molecular structure characteristics in the endosperm of Faba bean seeds

Abstract: Synchrotron radiation infrared micro-spectroscopy (SR-IMS) allows to investigate the inherent molecular components of biological tissues at a cellular and subcellular levels. To our knowledge, studies on the nutrient molecular properties in the tissue of Faba bean seeds (FBS) using SR-IMS are limited. Also, SR-IMS analysis of the effects of thermal processing, particularly of steam pressure toasting (SPT) on FBS are lacking. Therefore, the objective of this study was to determine the impact of SPT on the molecular composition of the endosperm tissue of FBS. This structure features will be used for associate study with animal nutrition. Spectra were collected in the mid-infrared region focusing on protein related spectral bands including amide I, amide II, amide I to II ratio, alpha-helix and beta-sheet and their ratio. Snowbird variety FBS were heated at 121°C for 0, 30, 60, 90, and 120 min in an autoclave (Amsco century, Steris). Cross sections from the processed seeds were mounted into BaF₂ windows (1 cm x 1 mm; n=45) and analyzed using the Synchrotron-radiation based infrared beamline laboratory at the Advanced Light Source-ALS Berkeley Lawrence National Lab (U.S. Dept of Energy, CA, USA). Spectroscopic data was collected using a Nicolet iS50 FT-IR spectrometer (Thermo Scientific) coupled with a Nicolet Nic-Plan IR Microscope (Thermo/Nicolet). The experiment design was a RCBD with nested structure. The mixed procedure of SAS was used for data analysis. The orthogonal polynomial contrast was used to detect linear, quadratic and cubic relationship between SPT processing time and molecular structure profiles. Results showed a lower absorbance in the amide I area (P < 0.01) of raw seeds (47.53 AU) compared to 30 min (54.16 AU) and 120 min (57.01 AU) treatments. Amide II area was higher (P =0.01) at 30 min (24.36 AU) compared to 60 and 90 min (22.06 and 22.16 AU, respectively). The α-helix to β-sheet ratio was higher (P < 0.01) in raw seeds (1.09 AU) compared to all heating times (avg. 1.01 AU). The use of Synchrotron technology was valuable to estimate the protein-related molecular composition and investigate the effects of steam pressure toasting in the endosperm of FBS. Compared to Globar-sourced vibrational FTIR, SR-IMS gives more detailed information about chemical-structural features and distributions in the tissues at cellular dimensions. Future study is needed to determine nutritional significance of molecular structure change induced by SPT in animals.