Production of hydrogels with different mechanical properties by starch roasting: A valorization of industrial chestnut by-products

Abstract The impact of chestnut starch (CS) roasting temperature and time on the starch composition, solubility, dextrin content and crystallinity degree as well as on the hydrogel forming profiles and viscoelastic features was evaluated. Monitoring of the thermorheological characteristics allowed determining the evolution of chestnut roasted starches in the presence (RCS) and absence (RCSI) of the soluble fraction after the use of different roasting temperatures (from 120 to 220oC). Textural profile analysis (TPA) of RCS hydrogels was employed to determine the hydrogels textural features. The largest dextrin content and starch solubility values were found in starch samples treated at 190oC (RCS190) for 10h, 210oC (RCS210) for 10h and 220oC (RCS220) for 6h. Amylose content and crystallinity degree of RCS samples showed a negative linear relationship. RCS hydrogels formed with starches roasted between 120 and 170oC exhibited intermediate strength and full thermal stable features. Hydrogels prepared from starches treated at 190 and 210oC promoted stronger and fully thermal stable hydrogels formation. RCS220 hydrogels presented equivalent strength, but no fully thermal stable characteristics. RCSI hydrogels strength decreased with rising roasting temperature. The absence of water syneresis was observed for RCS hydrogels aged for two weeks at room temperature, apart from RCS220 hydrogels. A relationship between textural parameters obtained by TPA and viscoelastic hydrogel features determined by rheological characterization was established.