Instant Rice Essay

Results and Discussion

Drying Characteristics

The drying curves of the instant rice by microwave drying from different rice cooking methods are shown in Fig 1. There are two stages of drying: moisture content is reduced rapidly and slowly when the drying is near completion. The first period is within 10 minutes of drying process; the moisture content is dramatically decreased. However after 10 minutes of drying, the moisture content slowly decreases when the moisture content is close to the completion state. At first, instant rice had a moisture content range of 64.79 to 70.83 (%db.) During first period of drying, the moisture content decreases in a linear manner, which is called a constant drying rate. Then the moisture content reduced slowly

Table 1 shows the hardness of dried instant rice after rehydration. It was found that the hardness of rehydrated instant rice was in the range of 32.54 - 37.24 N. Cooking with the pressure cooker (SPC and BPC), boiling (BL) and steaming (SM) did not significantly affected the hardness of rehydrated instant rice. The hardness of rehydrated instant rice corresponded to the volume expansion which was not significantly different after rehydration. The whiteness of cooking methods showed no significant difference with that of freshly cooked rice. Simultaneously, there was no significant difference in hardness. However, the cooking method did not affect the whiteness of instant rice. The volume expansion of BPC after rehydration in boiling water for 3 minutes is presented in Table 1. These results revealed that cooking method and drying with industrial microwave oven did not affect the volume expansion of rehydrated instant rice which is similar to the results of Prasert and Suwannaporn. From Table 1, it was found that the volume expansion of instant rice with the industrial microwave oven is less and this was consistent with Jiao et al., (2014), who found rapid drying resulted in less volume expansion. Due to the heat generated by drying, evaporation of water can be the cause of pores within the grain and resulting in volume expansion from the outer surface from long-term heating. It causes the volume expansion inside the