The present study examined the performance and separation
characteristics of XAD-16, SP-825, HP-20 and HP-2MGL resins for
purifying and enriching the peptides from soy sauce. The adsorption
process of all the resins exhibited two-stage changes before
an equilibrium after 60 min. The particle diffusion kinetics model
was the most favorable model for describing the whole adsorption
process on SP-825 or HP-20 resin for the peptides from soy sauce,
while the pseudo-second-order model was the most suitable model
for characterizing the behaviors of XAD-16 and HP-2MGL resins.
Further, it was found that the adsorption process was exothermic
(DH < 43 kJ/mol) following the Freundlich adsorption isotherm
rather than the Langmuir model. The XAD-16 and SP-825 resins
were more effective for peptide enrichment than HP-20 and
HP-2MGL resins, with differences in adsorption/desorption behaviors
due to their chemical and physical properties. The XAD-16
resin was the most suitable resin among the four examined resins
for purifying and enriching peptides from soy sauce, because of its
high adsorption and total desorption capacities. It is concluded that
non-polar resins with larger surface area and smaller pore diameter
would render a good adsorption capacity. Upon elution with
water or aqueous ethanol solution, the taste of XAD-0% ethanol
fraction containing the highest peptides and umami amino acids,
was much better than the XAD-20% and XAD-40% ethanol fractions.
This study provides new insights into exploring performance
and separation characteristics of macroporous resins on soy sauce,
and indicated that peptide may be the contributor to the umami
taste in Chinese soy sauce. On the basis of the results obtained
from this work, more work is worthy to be done to further purify
the umami peptide in the soy sauce.