IN-SITU INVESTIGATION OF PROTEIN-STRUCTURE IN PACIFIC WHITING SURIMI AND GELS USING RAMAN-SPECTROSCOPY

Raman spectroscopy was used to study the in situ protein structure in raw and salted surimi from Pacific whiting, and in gels formed by sett ing (32 degrees C), cooking (86 degrees C) or setting followed by cook ing. The set-cooked gel had a better gel strength and fold score than the gels which were only set or cooked. Large increases in relative in tensity of a band near 530 cm(-1) in the cooked and set-cooked gels in dicated changes in disulfide bond stretching or aliphatic chain vibrat ions. Involvement of hydrophobic interactions of aliphatic chains in s alting, setting and cooking was inferred from the decreased intensity of a band near 2930 cm(-1) assigned to C-H stretching vibrations. Chan ges in a doublet near 850 and 830 cm(-1) suggested an increasing invol vement of tyrosine residues as hydrogen bond donors in a non-polar env ironment after setting or setting-cooking, in contrast to increasing e xposure to a polar environment in gels formed by cooking alone. Second ary structure estimation based on the amide I band indicated a change from predominantly alpha-helical structure in raw surimi to higher ant iparallel beta-sheet and lower alpha-helical contents after setting an d particularly during the kamaboko stage. (C) 1997 Published by Elsevi er Science Ltd on behalf of the Canadian Institute of Food Science and Technology.