University of Salerno, Fisciano (SA), Italy
Starch-based hydrogels offer the possibility of providing suitable natural structures for innovative applications. High pressure technology (HHP) has been proposed as an alternative to traditional methods to produce hydrogels with reduced processing time and energy consumption. However, limited information on the final properties of starch-based hydrogels obtained with HHP treatments are available, as well as on the possibility of their functionalization, being the latter a very important aspect to be investigated in view of future applications of these innovative materials.
The aim of this work was to evaluate the influence of processing time and type of starch on hydrogel formation and on physical properties of the products obtained.
To this purpose, corn, rice, wheat and tapioca starches were suspended in distilled water (20% w/w) and subsequently treated at 600 MPa for 5 and 15 min at 25 °C. The treated samples were analyzed to determine swelling behavior, gel formation, rheological properties and texture profiles.
At 600 MPa, independently on processing time, the complete gelation of corn, rice, wheat and tapioca starch occurred, being the higher swelling values detected in hydrogels formed at processing time of 15 min. Whatever the type of starch and treatment time, all HHP induced hydrogels exhibited gel-like rheological properties with a shear-thinning behaviour (n<0.6). Experimental rheological data were well fitted with the Herschel-Bulkley model (R2>0.99). Additionally, when processing time of 15 min was set, all HHP-hydrogels showed increased strength with higher values of yield stress (?0), apparent viscosity (?app), hardness, adhesiveness, gumminess and chewiness (p<0.05).
In conclusion, it has been demonstrated that type of starch, pressure level and treatment time affected the physical properties of HHP hydrogels. Moreover, while hydrogels produced from rice, wheat and corn starch showed a creamy structure, tapioca-based hydrogels showed a compact structure.