the ratio calculated from the second derivative between absorbance
peaks 1660 cm1 and 1690 cm1 (Aparicio et al., 2002). This
ratio has been described to be indicative of reducible pyridinoline
and dehydro-dihydroxynorleucine that are specific cross-linkings
at the level of the telopeptide region, normally associated with collagen
ageing (Blank et al., 2003). A higher ratio 1660/1690 cm1 for
the WP compared to the FP salmon groups (3.48 vs. 3.18) indicates
that cross-links in which pyridinolines are taking place contributed
to collagen triple helix stabilisation and cross-linking (Johnston
et al., 2006; Li et al., 2005). Moreover, by DSC it was observed that
WP salmon had a higher denaturation peak temperature compared
with their FP counterparts (Table 1). This may be a consequence of
the greater amount of pyridinoline cross-linking that stabilised the
collagen molecule.