Effect of combined microwave, hot air, and vacuum treatments on cooking characteristics of rice

摘要

Instant rice is a precooked and dried, whole grain rice kernel, which can be prepared relatively in a very short period by adding boiled water. Precooking method employed plays a major role in lowering the cooking time while maintaining the quality of the product. The rice kernels were pretreated and then were subjected to convective hot air at temperature 70 degrees C for 90 min. The combination of microwave, hot air, and vacuum was also used in processing the rice kernels. Microwave power of 200 W for 2 min along with hot air at 70 degrees C for 90 min was used with vacuum of 400 mmHg for 2 min. The study found that the internal porous structure of the instant rice plays a crucial role in determining the physical characteristics like weight gain percent, hardness, and springiness. Based on weight gain percent, texture analysis, DSC, and SEM it was found that the combination of microwave (200 W for 2 min), hot air (70 degrees C for 90 min), and vacuum of 400 mmHg was the optimal processing condition for making instant rice that takes 2 min to cook. Practical applications Instant rice has a very short reconstitution time; hence, for convenience of preparation of the cooked rice within 2 min the instant rice is of immense value for those situated in very high altitudes, especially army personnel and also for the western countries. The study of the variation in the microstructure of the instant rice explains the mechanism of faster cooking. The preparation of instant rice requires no special cooking appliances and cooked rice matches with that of conventionally cooked rice. This data will also be very helpful for ready-to-eat food industries.