64. Measurement of processing and cooking qualities 2
- INDEX -
Characteristics of Cooked Rice
Water Uptake Ratio
Expanded Volume
Total Solids in Residual Liquid
Iodine Blue Value of Residual Liquid
Amylose
Amylose and Amylopectin
Measuring Method Using Sample of Powdered Milled Rice
Determination of Amylose Using a Sample of Rice Starch
Characteristics of Cooked Rice
Based on the method developed by Dawson in the U.S.A., Chikubu of the Food Research Institute developed a testing method to determine the characteristics of cooked rice using only a small amount of milled rice as a sample. Eight to ten grams of milled rice are put into a metal basket. The basket is hung within a tall beaker with excess water (approximately 160ml), and the beaker with the basket is placed in an electric rice cooker for thermal cooking. After cooking, the cooked rice is measured for expanded volume, water uptake ratio (WUR), weight of solid substance in residual liquid (total solid in residual liquid), and iodine blue value of residual liquid, IBV (dissolved amount of amylose in residual liquid). IBV is believed to have a high correlation with the amylose content, while IBV and WUR are said to affect the palatability of cooked rice.
Water Uptake Ratio
The water uptake ratio shows the water uptake of 8g of milled rice sample cooked in a 20-mesh metal basket of 10cm high and 4cm in diameter. The metal basket is weighed first. After cooking the cooked rice together with the metal basket is weighed, and calculated as:
Water uptake ratio = (weight of cooked rice) / (weight of milled rice sample)
Expanded Volume
Measure the height of cooked rice in the net basket at four different points using a pair of calipers after cooking is completed, and obtain the apparent expansion of volume using the following equation:
Expanded volume = πr2h,
r : radius of the net basket (cm)
h : height of the cooked rice (cm)