Kinetic Studies on Cooking of Rice

Abstract

The mechanism of cooking rice was investigated in this study. The rheological method using the parallel plate plastometer was adopted for measurement of the degree of cooking. The range of temperatures measured ran from 75-150°C. Experimental results showed that cooking rate followed the equation of a first order chemical reaction. We designated the proportional constant as the cooking rate constant, but the slope of Arrhenius plots of the cooking rate constants changed around 110°C. The activation energy of cooking at temperatures below 110°C and above 110°C was about 19,000 and 8,800 cal/mol respectively. The influences of water soaking time before cooking were also studied. We concluded that the cooking process comprises two mechanisms; at temperatures below 1 10°C the cooking rate is limited by the reaction rate of rice components with water; and at temperatures above 110°C it is limited by the rate of diffusion of water through the cooked layer toward the interface of uncooked core where the reaction occurs. The reaction rate constant and the diffusion coefficient of water were calculated by assuming the core model or shell-type model.

Cooking quality and instrumental textural attributes of cooked rice for different milling fractions

“…Since it was a slender grain (b = 1.64 mm), the water diffusivity could have been faster than Swarna (b = 1.71 mm) and ADT37 (b = 1.96 mm) variety for the same degree of milling. This confirms to earlier results reported by Suzuki, Kubota, Omichi, and Hosaka (1976). The coarser grain variety ADT37, took the highest optimum cooking time (for complete disappearance of white core) as compared to Pusa Basmati and Swarna.…”

Review of the effects of different processing technologies on cooked and convenience rice quality

“…The cooking rate is the amount of cooked rice as a function of cooking time, and is strongly 254 affected by the temperature and the amount of cooking water (Bello, Tolaba & Suarez, 2007; 255 Suzuki et al, 1976). When water temperature is increased to the gelatinisation temperature, starch 256 granules swell irreversibly, lose their crystallinity and gelatinise (Metcalf & Lund, 1985).…”

“…When a long grain variety was 259 soaked/cooked from 25 -90 °C, the water absorption curves showed a rapid increase in the 260 diffusion of water at around 65 °C (Bello et al, 2007). The changes in the activation energy for 261 diffusion and physical change at 60 °C indicate that below this temperature the structural change of 262 water and rice components was the limiting factor while above 60 °C the diffusion of water became 263 the limiting factor for water absorption with the gelatinised starch physically preventing penetration 264 of water (Bello et al, 2007;Suzuki et al, 1976). These results are consistent with the study of 265 Chakkaravarthi et al (2008).…”

Energy conservation in domestic rice cooking

“…The cooking of rice is associated with complete gelatinization of the starch, complex formation, transformation and interactions involving biopolymer by heat treatment in the presence of water. Suzuki, Kubota, Omichi, and Hosaka (1976) reported that cooking rate followed the equation of a first-order chemical reaction.…”