Prevention of the Retrogradation of Glutinous Rice Gel and Sweetened Glutinous Rice Cake Utilizing Pulsed Electric Field during Refrigerated Storage

Abstract

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

• glutinous rice grain
• starch retrogradation
• pulsed electric field (PEF)
• texture profile analysis (TPA)
• X-ray diffraction
• differential scanning calorimetry (DSC)