30H-15 |
Effect of spray drying on the oxidative stability of rice flour |
I. M. LIMA, H. S. Guraya, and E. T. Champagne. Food Processing & Sensory Quality Research Unit, USDA-ARS-Southern Regional Research Center, 1100 Robert E. Lee Blvd., New Orleans, LA 70124 Due to the relatively small amount of fat present in rice flour, rancidity problems are often underestimated. Upon storage, oxidative rancidity can render rice flour inappropriate for consumption, resulting in unnecessary monetary losses to the rice industry. An experiment was planned to study the effects of spray drying rice flour reconstituted with water in the reduction of lipid oxidation during storage. Rice flour from long, medium and short grain varieties was processed by passing a 14% rice flour slurry through a micro-fluidizer at 10,000 Psi and spray dryer at three different outlet temperatures, OT (50°C, 80°C and 115°C). Spray drying conditions were controlled by flow-rate of the slurry and inlet temperature. Spray dried rice flours and unprocessed rice flour were examined for their oxidative stability during storage in air-tight containers under moderate conditions (38 degree C) by measuring free fatty acid (FFA) formation. Rice flour lipids were extracted by soxhlet and FFA content was measured by titration with sodium hydroxide. Amount of FFA in rice flour was significantly reduced by spray drying. Reduction was rice variety dependent and proportional to the outlet temperature: 94%, 84% and 82% for long grain rice flour, 87%, 82%, and 61% for medium grain rice flour and 15%, 11% and 0% for waxy rice flour, at 115°C, 80°C and 50°C, respectively. Upon storage, levels of FFA in processed flours remained significantly lower than the controls (0.6% at OT=115°C and 4.7% at OT=80°C versus 24.5% (unprocessed) for long grain flours, and 4.1% at OT=115°C and 4.9% at OT=80°C versus 33.3% (unprocessed) for medium grain flours). Processing rice flour at 50 degrees C, however, led to a significant increase in FFA after 2 weeks of storage. In conclusion, spray drying can successfully prolong the shelf life of rice flour by significantly reducing oxidative rancidity.
Session 30H, Quality Assurance
|