shown) was similar to the present one (65 C, Fig. 2). For
instance, at 55 C CL varied between 9% (non-injected)
and 1.7% (0.50% STTP + 1.40% NaCl), and at 75 C,
between 14.8% (non-injected) and 4.0% (0.50%
STTP + 1.40% NaCl).
The linear and quadratic terms of STPP concentration
contributed significantly (p < 0.01) to pH variation Eq.
(2). Neither the other factors (NaCl and CT) nor their
interactions had significant effects (p > 0.05) on pH.
pH ¼ 5:75 þ 2:22STPP 2:15STPP2: ð2Þ
For Eq. (2), the adjusted coefficient was R2 = 0.5. pH as a
function of STPP concentrations was plotted in Fig. 3. It
can be seen that pH values increased almost linearly between
0% and 0.25% of STPP. After this value, pH increases at a
lower rate showing a tendency to a plateau between 0.40%
and 0.50% STPP.
The dependence of CL on the CT (Fig. 4) was obtained
fixing in Eq. (1), the STPP and NaCl concentrations in
0.25% and 1.20%, respectively (this combination has produced
the minimum CL value). The graph shows clearly
that the increment of the CT affected negatively the CL values,
finding the greatest losses at temperatures higher than
65 C.
Fig. 5 shows CL values at 65 C (obtained from) Eq. (1)
plotted against IS. This parameter was calculated using the
equation
IS ¼ 0:5X
i
aiciZ2i
; ð3Þ
where ai is the degree of dissociation of the salts (NaCl
ai = 1, STPP ai = 0.81, Trout & Schmidt, 1986b); ci is the