The effect of high hydrostatic pressure and pulsed electric fields were tested as pretreatments for moisture absorption of wheat grains. To measure the moisture, innovative and non-invasive sensor based on microwave technology was used. The results demonstrated that both technologies influenced the water uptake and the sensor exhibited good reliability and reproducibility of the measurements.

Abstract

The effect of high pressure (0.1–600 MPa) and pulsed electric field (E = 3 and 6 kV cm⁻¹) pretreatments on the moisture absorption properties of non-hulled wheat grains were investigated. Microwave sensor was used as a non-invasive technique for determination of the moisture content. The results demonstrated that high pressure soaking (>100 MPa) of wheat grains significantly increased the water uptake. High pressure soaking (600 MPa) decreased the water uptake due to the starch gelatinization and as a result appearance of structural changes. Compared to control samples, PEF-pretreated samples showed a sharp increase of water absorption at the initial process with a further reduction of equilibrium water content. Peleg's water absorption model was adapted to the measured data of non-hulled wheat grains. Results showed a good prediction of Peleg's equation in all experiments, which gave the possibility for estimation of initial water absorption rate and equilibrium moisture content.