Influence of packaging materials, oxygen and storage temperature on quality of germinated parboiled rice

In this study, the effects of storage conditions of germinated parboiled rice (GPR) including packaging materials, oxygen, and temperature on its physicochemical qualities, bioactive compounds, antioxidant activity, sensory quality, and microbiological properties were investigated. GPR from purple rice (Oryza sativa var. ‘Hom Nil’) was packaged under vacuum and normal atmosphere in polyamide-polyethylene (PAPE) and aluminum-laminated polyethylene (ALPE) pouches and stored at 4 °C and 30 °C for 6 months. The results showed that storage at lower temperatures under vacuum in ALPE was effective in retarding the degradation of bioactive compounds, changes in physicochemical quality, and rancidity. Moisture content and water activity continuously declined during the storage in PAPE pouches at 30 °C while they were unchanged when stored in ALPE at 30 °C and under all conditions at 4 °C. At 30 °C, the gamma-aminobutyric acid and anthocyanins contents decreased as the storage time increased, however the contents in samples at 4 °C did not vary with time. Total phenolic content and antioxidant activities were also effectively retained under low temperature storage, especially in vacuum packaging. Rancidity of GPR determined using the thiobarbituric acid test, increased with storage time and showed a high correlation with sensory evaluation results (R2 = 0.9724). Storage at 4 °C also significantly conserved the color of GPR. In addition, bacterial count, yeast and mold count and aflatoxins content of the GPR did not exceed Thai standards under all tested conditions.