Production of maltodextrin from rice flour by using alpha-amylase for polished rice aroma preservation

Production of maltodextrin DE (Dextrose Equivalent) 10, 15 and 20 from rice and waxy rice flour, obtained by using alpha-amylase (0.02 percent-0.05 percent of dry flour weight respectively) at 80 deg C, showed that the optimum solid contents of rice slurry and waxy rice slurry were 25 percent and 30 percent respectively. Liquefied starch, reducing sugar contents and DE values increased with increasing time (5-60 minutes). The production of maltodextrin from waxy rice flour gave about 1.5 times higher yield than that of rice flour. Major components of low molecular weight saccharides in maltodextrin were DP3 (3.60-6.52 percent), DP5 (4.76-8.20 percent), DP6 (5.10-7.12 percent) and DP7 (3.13-5.60 percent). At 10 percent solid, the viscosity of maltodextrin from rice and waxy rice flour was not different (4.50-5.25 RVU). But at 25 percent solid, the viscosity of maltodextrin from rice flour (6.00-7.00 RVU) was significantly higher than that of waxy rice flour (5.00-5.50 RVU) at the same DE. All 6 types of maltodextrin were used to preserve and improve polished rice aroma by 2 methods, coating aromatic rice with 25 percent maltodextrin (80 g/l kg rice) and coating nonaromatic rice with the mixture of 10 percent maltodextrin and 25 percent artificial pandan flavor (80 g/l kg rice). After keeping at room temperature (30 deg C) and 45 deg C, coated rice from these 2 methods as compared with common rice was less white, softer, lower in peak viscosity and breakdown by Rapid Visco Analyser Instrument (RVA). Sensory evaluation showed that aromatic rice coated with the waxy rice maltodextrin DE 20 had highest aroma, but not significantly different from common aromatic rice. And all types of coated aromatic rice were significantly softer than common aromatic rice. Nonaromatic rice coated with maltodextrin and pandan flavor had higher aroma and flavor than common rice. When this coated nonaromatic rice was mixed with common nonaromatic rice at ratio 1:3, it had aroma intensity as much as common aromatic rice. But when mixed at ratio 1:1, it had aroma intensity that consumers liked the most. From all 6 types of maltodextrin coated aromatic and nonaromatic rice, it could be concluded that the maltodextrin DE 15 from the waxy rice flour gave the best results and the most suitable.