Author : Anjar Ruspita Sari

Summary : Corn is used as a staple food to substitute rice by processing it into steamed corn grits, which is consumed particularly in central part of Java and Madura region, Indonesia. Unfortunately, there is minimum information on the process preparation of partially cooked corn grits (PCCG) in traditional way. Moreover, the traditional preparation of PCCG is time-consuming and it is attributed as inferior food. Therefore, the objectives of this research were to optimize the processing condition and subsequently, to evaluate the effect of microwave pre-treatment prior to hot air drying on PCCG preparation. The initial moisture content (30%–45%) was modified to achieve optimum properties of PCCG prepared using the traditional process. Whereas, the new improved process was developed through optimization of processing parameters—namely, corn particle size (0.30–1.40 mm), initial moisture content (40%–60%), and processing temperature (115°C–126°C) using response surface methodology (RSM). The properties of optimized PCCG prepared using the traditional and new improved processes—namely, water absorption index (WAI), water solubility index (WSI), yellowness index (YI), and resistant starch (RS) of dried PCCG—as well as textural properties of rehydrated PCCG were compared to obtain the best PCCG. Subsequently, the best PCCG was dried using microwave pre-treatment of hot air drying at various microwave power level (low–high), microwave exposure duration (10–30 seconds), and temperature (50°C–70°C). Results showed that the optimum initial moisture content to prepare PCCG by the traditional process was 40 percent. Meanwhile, the optimum processing conditions to prepare PCCG by the new improved process through RSM were 0.30 mm particle size, 52.33 percent initial moisture content, and 123.67°C processing temperature. PCCG prepared using the new improved process had significantly higher value of YI (99.51 ± 0.21) and almost double value of RS (3.65 ± 0.08%). The textural properties of rehydrated PCCG, except for adhesiveness prepared using the new improved process were not significantly different (p ≥ .05) with the traditional one. Furthermore, the new improved process also had shorter PCCG preparation time, which was 4–6 hours compared to the normal, which was 3–4 days in the traditional preparation. Subsequently, temperature was the most significant factor (p < .05) that affected drying kinetic of PCCG. The higher drying temperature resulted in higher drying rate, better water absorption, and more homogenous surface pore of dried PCCG, as well as lower hardness and higher adhesiveness of rehydrated PCCG. Meanwhile, the pre-treatment microwave only affected surface pore of dried PCCG. The drying process conditions of PCCG were achieved at 70°C hot air drying temperature. In conclusion, convenient PCCG could be prepared with the following conditions: first, gelatinization process using 0.30 mm corn particle size, 52.33 percent initial moisture content, and 123.67°C processing temperature; and second, the hot air drying at 70°C drying temperature.