Quality Evaluation of Parboiled Rice with Physical Properties.

Abstract

This study was undertaken to generate useful information regarding the change of quality of parboiled rice for different processing conditions through the change of physical properties and to search for correlation among the quality indicators. Physical properties, namely, maximum viscosity, hardness of brown rice, hardness and adhesion of cooked rice, volume expansion ratio and solid content were investigated. A first order kinetic model predicted well the effect of processing conditions on the maximum viscosity and hardness of brown rice, indicating the quality index and rate of change of quality with their respective final and reaction rate constant values. The effect of steaming period was found to be greater on the quality indicators of cooked rice, such as adhesion, volume expansion ratio and solid content. Good linear correlation of gelatinization property with the cooking quality and rheological property of parboiled rice was achieved. The positive correlation between adhesion and solid content is assumed to be responsible for producing a less sticky product.Keywords: quality evaluation, parboiled rice, physical properties, parboiling processThe parboiling process is a big share of the global rice processing industry. Generally, the majority of the population of a developing country consumes parboiled rice. This is especially true on the Indian Sub-continent, where it was originated a long time ago. It was reported that about one-fifth of the world's rice is parboiled (Bhattacharya, 1985). This production seems to be increasing day by day, because the growth rate of the population in these countries is higher and a major part of the food value comes from rice itself. Parboiling is the hydrothermic treatment given to rough rice. As a result, the physicochemical properties of the rice are changed (Roberts et al., 1954;Kurien et al., 1964;Bhattacharya & Subba Rao, 1966;Bhattacharya & Indudhara Swamy, 1967;Raghavendra Rao & Juliano, 1970;Gariboldi, 1972;Kimura, 1983;Bhattacharya, 1985;Itoh & Kawamura, 1985;Kimura, 1991;Kimura et al., 1993;Unnikrishnan & Bhattacharya, 1995), which affects the milling quality, nutritional value and storability of grain. It consists of soaking, steaming and drying. This treatment also leads to the final product of the cooked parboiled rice, having a favourable texture for those who eat it. There is much in the literature available regarding the physicochemical properties, milling, cooking and eating quality of parboiled rice. To better understand the quality it is worth knowing how the physical properties affect the quality of the rice with the change of processing conditions. This study was undertaken to provide useful information to the processors as well as to the consumers of parboiled rice regarding the change of quality for different processing conditions through the change of physical properties and to search for correlation of some quality indicators with others. The objectives of this paper are: i) to study the effect of parboiling on the physical properties of rice su...

Effect of Processing Conditions on Physical Properties of Parboiled Rice.

“…The hardness of parboiled rice depends on the severity of the parboiling treatment. Many researchers reported hardness is greatly affected by parboiling conditions, moisture content after drying, elapsed time, the balance of starch gelatinization and retrogradation and other factors (Ali & Bhattacharya, 1976;Pillaiyar & Mohandoss, 1981;Bhattacharya, 1985;Itoh & Kawamura, 1985;Kimura, 1991;Islam et al, 2001). Figure 6 shows the effect of parboiling treatment on the hardness of brown rice for different steaming conditions and sample sizes.…”

“…3. Brown rice grains were put on the sample table attached to the load cell and their bio-yield point value measured in a flat position (Kimura, 1991;Islam et al, 2001). A 245.2 N load cell, a probe of 2 mm diameter and 0.1 mm/s compression rate were used.…”

“…This starch gelatinization changes the physicochemical properties of rice (Bhattacharya & Subba Rao, 1966;Bhattacharya & Indudhara Swamy, 1967;Raghavendra Rao & Juliano, 1970;Gariboldi, 1972;Kimura, 1983;Bhattacharya, 1985;Itoh & Kawamura, 1985;Kimura, 1991;Kimura et al, 1993;1995;Islam et al, 2001), which affects the other processing operations of storage, milling, cooking and eating quality. Islam et al (2001) evaluated the quality of parboiled rice by its physical properties of maximum viscosity, hardness of brown rice, hardness and adhesion of cooked rice, volume expansion ratio and solid content, utilizing the first-order kinetic model. They identified the rate of change of quality and the quality index of parboiled rice with the reaction rate constant and final values of the quality indicators.…”

Effect of ingredients on sensory profile of idli

“…Roy et al (2010) noted that the hardness and adhesion of cooked rice were dependent not only on the moisture content but also on the forms and variety of rice. Roy et al (2004Roy et al ( , 2008, Islam et al (2001) and Shimizu et al (1997) reported that the hardness of the cooked rice depend on the moisture content of cooked parboiled and untreated rice. In case of idli, steaming increases the moisture content of idli and it is a major factor that makes idli made with parboiled rice softer and for the same reason that red rice has acquired more moisture which affected its texture losing firmness.…”

“…The parboiling treatment given to rice decreases the stickiness (Roy et al 2004;Kato et al 1983;Biswas and Juliano 1988;Islam et al 2001). Rice with low amylose content is generally soft when cooked, whereas rice with high amylose content has higher grain hardness (Juliano 1971).…”