Screening the Effect of Gelatinization Temperature and Cold Water Soaking on Functional Properties of Selected Traditional Rice Varieties in Sri Lanka

Abstract

At present traditional rice varieties are gaining recognition in Sri Lanka as potential raw material for new food products due to their high nutritional value and high adaptability to the local environmental conditions. However, utilization of rice flour in the bakery industry is limited due to the lack of gluten in flour which is essential for maintaining the desired quality of the products. The objective of this study was to modify rice flour varieties by adapting physical treatments, thus improving the functional properties making flour suitable for the fabrication of bakery products. Traditional rice varieties namely Madatuwalu, Kaluhenati, Panchaperumal and Rathdal, were taken and moisture content was allowed to increase up to 16.5% by adding calculated amount of water and soaking in water overnight. Soaked grains were subjected to a heat treatment at 85oC or 95oC for 3-5 minutes followed by dipping in cold water (4oC) for 1 or 2 hours. Functional properties of the treated rice flour such as, Water Solubility (WS), Swelling Power (SP), Water Absorption Index (WAI), and pH, were determined. Rice flour of all four varieties without any treatment served as the control. The treatments tested, soaking time and gelatinization temperature, had a significant positive effect (p< 0.05) on the functional properties of flour of all four selected traditional rice varieties. Treated flour of Madatuwalu and Rathdal showed significantly higher WAI and SP compared to all other treatments. This study demonstrated that the simple physical treatments of rice grains could improve the functional properties of rice flour making them more suitable for the bakery industry.