Starch-Based Hydrogels Produced by High-Pressure Processing (HPP): Effect of the Starch Source and Processing Time

Starch-based hydrogels are natural polymeric structures of high scientific interest in the food, pharma, and cosmetic sectors. In this work, the effects of the starch source (rice, corn, wheat, and tapioca starch) and processing time (600 MPa for 5 and 15 min) on gel formation and on the physical characteristics of the structures formed were evaluated. At the pressure level utilized, all the starches were completely gelatinized regardless of the processing time tested. The hydrogels obtained displayed a shear-thinning and gel-like behavior (G' > G"). HPP, under the processing conditions tested, was more effective in producing hydrogels based on tapioca and rice than on corn and wheat starch. Rice, wheat, and corn starch HPP hydrogels showed a cream-like structure, whereas those based on tapioca starch evidenced a more compact structure. With a HPP processing time of 15 min, tapioca and rice starch HPP hydrogels displayed higher viscosity, G', and firmness, suggesting an overall structural reinforcement. However, with 15 min of processing time, the lightness and whiteness of rice, wheat, and corn starch HPP hydrogels were negatively influenced, presumably as a consequence of the increased amount of water absorbed in starch granules. These results suggest that both the starch source and processing time play an important role in the formation of gels from starch suspensions and affect the physical characteristics of HPP hydrogels. Finally, the natural products obtained might be suitable for use in several applications where either creamy or gummy structures are desirable.