Mechanical property and quality aspects of rice dried in industrial dryers

Study of Selected Physical-Mechanical Properties of Corn Grains Important from the Point of View of Mechanical Processing Systems Designing

Mechanical properties of corn grains are of key importance in a design of processing machines whose energy demand depends on these properties. The aim of this study is to determine the selected mechanical properties of corn grains and the rupture energy. The research problem was formulated as questions: (1) How much force and energy is needed to induce a rupture of corn grain maintaining good quality of the product of processing (mixing, grinding transport)? (2) Can empirical distributions of the studied physical-mechanical properties be described by means of probability distributions provided by the literature? (3) Is there a relationship between the corn grain size and the selected mechanical properties, as well as rupture energy? In order to achieve the goals, the selected physical properties (size, volume) of corn grains have been distinguished and a static compression test has been carried out on an Instron 5966 testing machine. The results indicate a significant scatter of the results in terms of size, grain shape, forces, energy, and deformation corresponding to the point of inflection, bioyiled point, and rupture point. It has also been indicated that empirical distributions of the analyzed properties can be described by means of distributions known from the literature, e.g., gamma, Weibull or lognormal distributions. It has been confirmed that mechanical properties such as force, energy, and stress that cause rupture depend on the grain size, more precisely, the grain thickness-there are negative relations between thickness and force, energy and stress in relation to the point of inflection, bioyiled point, and rupture point.

Mechanical and Processing Properties of Rice Grains

Strength properties of grains have a significant impact on the energy demand of grinding mills. This paper presents the results of tests of strength and energy needed the for destruction of rice grains. The research aim was to experimentally determine mechanical and processing properties of the rice grains. The research problem was formulated in the form of questions: (1) what force and energy are needed to induce a rupture of rice grain of the Oryza sativa L. of long-grain variety? (2) what is the relationship between grain size and strength parameters and the energy of grinding rice grain of the species Oryza sativa L. long-grain variety? In order to find the answer to the problems posed, a static compression test of rice grains was done. The results indicate that the average forces needed to crush rice grain are 174.99 kg m·s−2, and the average energy is 28.03 mJ. There was no statistically significant relationship between the grain volume calculated based on the volumetric mass density Vρ and the crushing energy, nor between the volume Vρ and other strength properties of rice grains. In the case of Vs, a low negative correlation between strength σmin and a low positive correlation between the power inducing the first crack were found for the grain size related volume. A low negative correlation between the grain thickness a3, stresses σmin and work WFmax was found as well as a low positive correlation between thickness a3 and the force inducing the first crack Fmin.

Impact of physicochemical properties on duration and head rice yield during abrasive and friction milling of rice

The physicochemical properties of four rice varieties representing high amylose (Jyothi and IR64), intermediate amylose (Taraori Basmati) and waxy (Agonibora) were evaluated to understand their influence on milling. Based on the grain dimensions, Jyothi and Agonibora were classified as long and medium, IR64 as long and slender, and Basmati as extra-long and slender. The head rice yield (HRY) was higher with abrasive milling (61-75%) compared to friction milling (10-60%) although it required longer milling duration. Lower grain thickness, hardness and, amylose and higher bran fat content reduced the friction milling duration while these properties prolonged the duration in abrasive milling. Agonibora variety with low amylose content and high-fat content exhibited the highest HRY in both the types of milling. The study revealed that the selection of milling process should be made with due importance to grain geometry as well as its chemical properties.