Effect of microwave processing on physicothermal properties, antioxidant potential, in vitro protein digestibility and microstructure of durum wheat semolina

Abstract

The effect of microwave treatment on the physicothermal properties, antioxidant activity, protein digestibility and structural features of durum wheat semolina was investigated by varying time periods (1, 1.5 and 2 min) in a microwave oven set at 900 W. Results suggested that microwave treatment on durum wheat semolina caused a significant improvement in functional properties like water holding capacity (1.91 ± 0.08 to 2.63 ± 0.04 g/g), oil holding capacity (2.25 ± 0.36 to 3.05 ± 0.09 g/g), swelling power (6.08 ± 0.06 to 9.23 ± 1.15 g/100 g) and solubility (0.11 ± 0.01 to 0.13 ± 0.15 g/100 g). Overall colour difference (∆E*) increase from 22.63 ± 0.36 (untreated) to 31.14 ± 0.27 (2 min), while significant decrease in gelatinization enthalpy (2.49 ± 0.08 to 1.53 ± 0.09 J/g) and peak viscosity (1501 ± 5.29 to 127 ± 3.60 cP) was seen after the treatment. Total phenolic content (free + bound) decreased from 2.61 ± 0.01 to 0.98 ± 0.03 mg GAE/g, while antioxidant activity expressed as inhibitory concentration (IC50) improved (1.60 ± 0.05 to 0.79 ± 0.01 mg/ml) as microwave heating progressed. In vitro protein digestibility decreased significantly (71.35 ± 0.05 to 53.64 ± 0.04%) as the duration of microwave heating increased. Microstructure examination revealed small defects and rupturing of starch granules, whereas FTIR spectra of durum wheat semolina did not change by microwave heating.