Thermoproteus uzoniensis 4-α-glucanotransferase catalyzed production of a thermo-reversible potato starch gel with superior rheological properties and freeze-thaw stability

Solid-liquid thermo-reversibility, lacking in raw starch is an important property for gels allowing repeated thermal processing in food. In this work, the Thermoproteus uzoniensis 4-alpha-glucanotransferase (Tu alpha GT) was used to modify five different starches from potato, corn, rice, wheat, and pea and the thermo-reversibility of the modified starch gels was evaluated by rheological assay. Only modified potato starch (MPS) exhibited thermo-reversibility, which prompted us to perform detailed analyses of the structural and gel properties of this product. The enzymatic modification resulted in a marked decrease in amylopectin side chains with a degree of polmerization (DP) < 23, while the contents of side chains with DP 23-43 increased. These data indicated that Tu alpha GT preferentially extended the outer chains of amylopectin using amylose as a donor, which resulted in 17% increase in the amylopectin molecular weight to 3.0 x 10(7) g/mol. Notably, MPS displayed a delayed retrogradation and improved stability in four freeze-thaw cycles (-70 ?C and 25 ?C) as compared to the native starch. These analyses supported a model to explain the Tu alpha GT catalyzed conversion of potato starch to a thermo-reversible product. Importantly, the MPS thermo-reversible 6% (w/v) gel showed comparable rheological properties to a 1.5% (w/v) kappa-carrageenan hydrocolloid, highlighting the potential of MPS as a substitute to kappa-carrageenan and other hydrocolloids of emerging health concerns. This work offers a starch based thermo-reversible gel and a methodological framework to broadens the use of starch into novel application as a food ingredient.

Automated summary

In this study, five different starches were modified using enyzmes, and the thermo-reversibility of the modified starch gels was evaluated. The results showed that modified potato starch exhibited thermo-reversibility and improved stability. This suggests that modified potato starch has the potential to be used as a substitute for kappa-carrageenan and other hydrocolloids in food applications.