Different Milling Methods: Physicochemical, Pasting and Textural Properties of Rice Flours

Abstract

Rice grains are consumed as staple food in many Asian countries and rice flour is used as a main ingredient in many products for various uses. Consumers prefer rice and rice flour because it is a source of carbohydrate and is highly nutritious and contains non-allergic protein and high amounts of unsaturated fatty acid ({\textgreater}70\%) as well as bio-active compounds such as Gamma-oryzanol, vitamin E and phytosterols1. Food producers prefer rice and rice flour due to low price, large volume of production and its acceptance by customers. The chemical composition and physicochemical properties of rice and rice flour must be studied to utilize the suitable rice for product development with desired characteristics. The information provided by the current study may encourage rice utilization as an alternative ingredient in various products. The milling method is one of the factors affecting the chemical composition and physicochemical properties of rice flour2. There are three milling methods: (1) Dry milling involves cleaning the rice grains using air blowing and then grinding to obtain a powder. This flour has rather low quality because of the coarseness of the powder, the high level of contaminants (dust, husk, stone), its short storage time and high rancidity as well as large amounts being lost to insect damage. The advantages of dry milling are less waste and the low level of loss during the actual milling (2) Wet milling is widely used for rice production especially in Thailand and Asian countries to produce a high quality, fine powder with fewer contaminants. The large volume of wastewater is a disadvantage of wet milling. (3) Semi-dry milling developed from wet and dry milling3. The rice grain moisture content is adjusted to about 25\% before milling and then the moist flour is dried in a hot-air oven. Milling methods had a marked effect on the properties of flour2-4. Both milling method and rice varieties with varying amylose content were studied in this research. The objectives of the current study were to investigate the effect of milling methods and rice varieties with varying amylose content on the chemical composition and the physicochemical, pasting and textural properties of rice flour.