Dj. Sessa et Tc. Nelsen, THERMAL-STABILITY OF SOY STORAGE PROTEINS IN CRACKED BEANS HYDRATED WITH A VARIETY OF SALTS, Lebensmittel-Wissenschaft + Technologie, 27(6), 1994, pp. 556-563
Various salt solutions used to hydrate full-fat cracked soybeans affec
ted the thermal stability of both beta-conglycinin (7S) and glycinin (
11S) storage proteins when examined by differential scanning calorimet
ry used to monitor both denaturation temperature (T(d)) and enthalpy (
DELTAH). As salt ionic strength (mu) increased, the moisture in the hy
drated beans decreased. When beans were hydrated with water only, heat
stability of both storage proteins increased with moisture decrease.
No change in DELTAH was observed. Since all salt treatments showed sim
ilar decreases in moisture with increased mu no adjustment for moistur
e effects was needed. Except for Na2CO3 all salt hydrations gave incre
ased protein thermal stability. Ranking of salts according to ability
to stabilize soy storage proteins at mu = 1.2 were: for beta-conglycin
in, NaH2PO4 > NaC2H3O2 > NaCl > Na2S2O5 > Na2SO3 > Na2SO4 > Na2CO3 > C
aCl2; for glycinin, NaC2H3O2 > NaH2PO4 > NaCl > Na2SO4 > Na2S2O5 > Na2
SO3 > CaCl2 > Na2CO3. The DELTAH's of the first two salts in the 7S se
ries and the first three in the 11S series were significantly higher t
han either moisture alone or all other salt treatments. When salt trea
tment data were evaluated on a molar concentration rather than mu, the
neutral salt hydrations followed the lyotropic series for stabilizati
on of proteins. Responses of both beta-conglycinin and glycinin differ
ed slightly. These differences were attributed to differences in elect
rostatic profile and response to water availability for these proteins
.