Physical and structural changes induced by high pressure on corn starch, rice flour and waxy rice flour

The impact of high pressure (HP) processing on corn starch, rice flour and waxy rice flour was investigated as a function of pressure level (400 MPa; 600 MPa), pressure holding time (5 min; 10 min), and temperature (20 °C; 40 °C). Samples were pre-conditioned (final moisture level: 40 g/100 g) before HP treatments. Both the HP treated and the untreated raw materials were evaluated for pasting properties and solvent retention capacity, and investigated by differential scanning calorimetry, X-ray diffractometry and environmental scanning electron microscopy. Different pasting behaviors and solvent retention capacities were evidenced according to the applied pressure. Corn starch presented a slower gelatinization trend when treated at 600 MPa. Corn starch and rice flour treated at 600 MPa showed a higher retention capacity of carbonate and lactic acid solvents, respectively. Differential scanning calorimetry and environmental scanning electron microscopy investigations highlighted that HP affected the starch structure of rice flour and corn starch. Few variations were evidenced in waxy rice flour. These results can assist in advancing the HP processing knowledge, as the possibility to successfully process raw samples in a very high sample-to-water concentration level was evidenced.