1. Nutritional Values of Rice

The rice grain consists of rice husks, cortex, embryo and endosperm, the weight percentage of which is 18~21% of the husk, about 6% of cortex, 66~70% of endosperm and 2~3% of embryo respectively. And the chemical composition of each part is different, rive husks contain about 40% of fiber which possess little nutritional value; the cortex rice in fat and protein as well as riches in the fiber; the embryo contains a lot of protein, fat, and vitamins; the endosperm is with the least fiber content and carbohydrates compare these three elements.

2. Development of Rice Processing Technology

The aim of rice processing is to separate the endosperm from other parts with the smallest degree of fragmentation, thereby producing high quality of rice. The main rice processing steps can be divided into paddy cleaning, paddy husking, and rice milling.

rice processing steps

2.1 Paddy hulling process

The process of paddy husking is to remove rough rice shells to make it for brown rice. The husk is removed by friction as the paddy grains pass between two abrasive surfaces that move at different speeds. The machine that used for husking paddy is called Paddy Huller Machine, the most commonly used rice huller is a rubber roller hulling machine. The main components of the roller hulling machine are a pair of parallel rubber rollers that rotated in opposite directions with the different. Peripheral. The shell of grains will be removed under the press and twist force of the two rollers. Rice is not completely hulled after the first hulling, and about 20% of the paddy is not hulled, so the materials after the hulling ( brown rice, paddy, and rice gluten, etc.) should be separated from brown rice by using paddy separating equipment, and then, re-hull the rice back into the hulling machine to achieve the effect of efficient hulling purpose.

2.2 Paddy De-cleaning Process— There are some impurities such as sand, clay, coal, nails, rice straw and weed seeds, and so on in rice. Efficient cleaning of these impurities in rice can not only provide high-quality cleaning rice for people but also improve the quality and market value of rice

2.2.1. Cleaning rice according to its volume–to choose the suitable screening sieve according to the different width and thickness of rice and impurities, which can effectively clean the impurities in rice.

2.2.2. Cleaning rice according to its length–to choose the screening sieve according to the length of the rice and impurities. This kind of screen is engraved with hemispherical sieve hole with a curved or round face when the screening screen begins to rotate, the short grain will be embedded into the curved sieve hole and be thrown out when reached a certain height; while the long grain can not be embedded in the curved sieve hole, and flow out from another side of the machine. Such a kind machine includes TQLM Series Rotary Paddy Cleaner, which can ensure sufficient screening for high cleaning efficiency.

2.2.3 Winnowing Cleaning: to use the screening sieve according to different gravity and suspended velocity of rice and impurities. So, impurities with the light quality (such as chaff, rice straw, etc,) will be separated from rice under the wind force in the rising or horizontal airflow. TQSX Series Paddy Destoner is the ideal grain cleaning equipment in the grain processing industry.

2.2.4 Gravity Cleaning–to choose cleaning equipment according to the different proportions of rice and gravel. Grains and stones are separated into two layers in the oblique vibration of the screen surface under the force of airflow and linear reciprocating vibration of sieve, grains are graded automatically after they enter into the upper sieve, stones stay on the sieve’s surface due to its gravity and being discharged from the outlet, the rice will floating in the upper layer. Among so many paddy de-stoners, TQSF Series Gravity Destoner is considered the advanced and cost-effective one.

2.3 Rice Milling Process–After the process of hulling, the surface of the cortex contains more fiber that affects the quality and taste of rice. Milling of brown rice means to crush the cortex. The working principle of Rice Milling Machine is to crush the cortex by the rice mill friction and grind. The main parts of rice mill are whitening chamber with rotating roller and local pressurization device (rice knife, pressure screen section), the external rice screen which used to exclude from the rice on the milled rice bran.

In order to reduce the pressure of rice grain in the milling process, to reduce broken rice and make the brown rice to high-precision rice generally required by two to four rice milling process for gradually crushing the cortex. Grinding out of the finished rice to be finished, including the use of rice separating machine to separate the complete rice and broken rice.

milled rice of high quality

All steps listed above are an inevitable part of a complete set rice milling plant. If you want to manufacture high-quality rice to satisfy customers’ tastes, there are 2 essential things you should know: a) Detailed analysis on your local market; b) enough money to purchase advanced rice processing machines.