Pulsed electric field (PEF) processing is an emerging non-thermal technology that shows the potential to improve food quality and maintain stability. However, the attributes and retrogradation properties of food products made of PEF-treated rice grains are still unknown. In the current study, glutinous rice gels (GR-G) and sweetened glutinous rice cakes (GR-C) made of PEF-treated rice grains were prepared and investigated during 14 days of storage at 4 °C. The hardness values of both the GR-G and GR-C-control samples, respectively, increased from 690 g to 1423 g and from 720 g to 1096 g; the adhesiveness values of the GR-G-control and GR-C-control samples decreased to the range of -7.2 g s to -10.0 g s during storage. PEF-treated samples (3 kV/cm, 400 pulses) resulted in preventing effects against retrogradation, resembling the original textural values of the freshly prepared control samples. The high intensity of imposed PEF treatment (300-400 pulses) significantly reduced the gelatinization enthalpy values of both GR samples to 0.3-0.7 J/g. The diffraction patterns of PEF-treated GR samples were analogous to the amorphous peak of fresh-made rice gel. FTIR results indicated that PEF-treated rice grains presented fewer crystalline regions and a lesser extent of the organized double helices after refrigerated storage.
Keywords: X-ray diffraction; differential scanning calorimetry (DSC); glutinous rice grain; pulsed electric field (PEF); starch retrogradation; texture profile analysis (TPA).