Desulfated carrageenan was prepared by reaction with 0–10 U
of purified Gal-6-sulfurylase under optimum experimental conditions.
As shown in Fig. 4, enzymatic treatment gradually decreased
the sulfate content, as well as, increased the gel strength of carrageenan
when subjected to 2–10 U of Gal-6-sulfurylase, while no
appreciable change in these parameters observed when enzyme
concentration was >10 U. The sulfate content of carrageenan
decreased remarkably from 20.1% to 14.4% by reaction with 10 U
of Gal-6-sulfurylase that corresponded to reduction of about 28.5%.
The enzymatic desulfation improved the gel strength as it enhanced
its value from 228.4 g/cm2 in control carrageenan to 1630.2 g/cm2
in 10 U enzyme treated carrageenan, contributing to almost 7.1-fold
increase. Carrageenan samples under different enzyme activities
showed a good negative correlation (r =
−0.9562) between the sulfate
content and gel strength: lower sulfate content raises the gel
strength