Degradation of κ-carrageenan by hydrolysis with commercial α-amylase

► The concept of degradation of κ-carrageenan by α-amylase is modest. ► The content in the product and the yield of carrageenan oligosaccharides are very high. ► The hydrolysis conditions were optimized. κ-Carrageenan was degraded by hydrolysis using commercial α-amylase (4000U/mg). The hydrolysis process was monitored by the intrinsic viscosity [η] of the hydrolysates. Factors affecting the enzymatic hydrolysis of carrageenan were investigated, and the optimum hydrolysis conditions were as follows: duration, 4h; pH, 7.5; temperature, 50°C; and amount of commercial α-amylase, 40mg of the mixture containing 5g κ-Carrageenan. Under the optimized conditions, minimum intrinsic viscosity (12.31) was obtained. The dextrose-equivalent value of the resulting products was 20.41, indicating that the average degree of polymerization was approximately equal to 5.0. The hydrolysates were filtered, concentrated to ∼15% (w/v), and precipitated with 6 volumes of ethanol; the precipitates were then freeze-dried to yield a white, water-soluble powder. The carrageenan-derived oligosaccharide content of the product and the yield were 96.5% and 92.6% (w/w), respectively.