Optimization of operating process parameters for instant brown rice production with microwave-followed by convective hot air drying

• Instant or quick cooking brown rice was produced by using microwave drying.
• Processing conditions for producing instant brown rice were optimized.
• Color, rehydration ratio and textural qualities of instant rice were determined.
• This research is useful for raising the market value of rice.

Nowadays, instant or quick cooking brown rice is a food product that has marketing potential due to the life style of new generation. This research mainly aimed to characterize, model and optimize the key processing conditions including water-rice ratio (WRR), microwave power level (MWL) and hot air temperature (HAT) for producing instant brown rice by applying Box-Behnken technique. The process responses comprised with color, rehydration ratio and textural qualities of products. The microscopic images of products were also determined. The result indicated that MWL caused the most intense effect on the rehydration ratio and textural qualities. Furthermore, the MWL and HAT influenced on the lightness while the WRR affected on the hardness of rehydrated samples. All three processing parameters significantly affected on the color intensity and stickiness of rehydrated rice. The optimal processing conditions for WRR, MWL and HAT were 1.44, 499.8 W and 89.99 °C respectively with 88% overall desirability.