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Title: EFFECTS OF BOUND WATER ON FTIR SPECTRA OF GLYCININ

Author
item Abbott Dr, Thomas
item NABETANI, HIROSHI - NATL FOOD RES INST
item Sessa, David
item Wolf, Walter
item LIEBMAN, MICHAEL - VYSIS
item DUKOR, RINA - VYSIS

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Soy protein is a major food component. When the soy protein is heated in foods it changes. Manufacturers of processed soy foods see the changes in properties but the basic reasons for the changes are not well understood. This work was done to determine the basic nature of soy protein and to learn what happens when soy protein is heated. This work will lay the groundwork for all protein structure-property studies where water and protein interact to affect structure.

Technical Abstract: Glycinin, a major storage protein in soybeans, is denatured by moist heat treatment. To study secondary structure changes that take place in glycinin upon hydration using infrared spectroscopy, it is important to remove the effect of bound water from the protein spectra. We have examined the effects of added water on glycinin infrared spectra. Glycinin containing from 2.6 to 95% water showed significant broadening in the amide I region and changes in the amide I to amide II maximum absorbance ratio with increased water content. Using a spectral ratio method to derive coefficients for multiplying and subtracting spectra, the bound water component spectrum and protein component spectra were obtained. The spectrum of dry glycinin could then be regenerated by subtracting the bound water component from glycinin that had added water. Curve-fitting of deconvoluted spectra gave the same secondary structure at all levels of added water after water was subtracted from the spectra (30% beta, 24% helical, 35% turns and 11% unordered). Spectra of glycinin in aqueous buffer were also determined, sidechain contributions removed and the resulting secondary structure found to be 33% beta, 25% helical, 31% turns and 12% unordered. This compares to 32% beta, 21% helical, 34% turns and 14% unordered before sidechain contributions were subtracted.