M. Nonaka et al., RAMAN-SPECTROSCOPIC STUDY OF THERMALLY-INDUCED GELATION OF WHEY PROTEINS, Journal of agricultural and food chemistry, 41(8), 1993, pp. 1176-1181
Alpha-lactalbumin and beta-lactoglobulin solutions [15 % (w/v) in D2O,
pD 6.8, 20 mM NaCl] were heated at 50, 70, or 90-degrees-C for 30, 60
, or 90 min. Only the samples heated at 90-degrees-C formed transparen
t gels. The amide I' and amide III' bands of the Raman spectra implica
ted an increase of beta-sheet structure with a simultaneous decrease o
f helical structure in heated alpha-lactalbumin, while an increase of
beta-sheet with a simultaneous decrease of turn structure was suggeste
d in heated beta-lactoglobulin. Changes in other regions of the Raman
spectra could be interpreted as changes in disulfide conformation as w
ell as in microenvironment around several amino acid residues, i.e., T
rp, Tyr, and His. These changes were observed after heating at 70 and
90-degrees-C but were more intense in the gelled (90-degrees-C) than i
n the ungelled samples and in beta-lactoglobulin than in alpha-lactalb
umin. These observations are in accord with the fact that beta-lactogl
obulin forms gels much more easily than alpha-lactalbumin.