Rice is a particularly popular crop all over the world and it offers the opportunity to grow different varieties of grains. It is a basic element in the nutrition of almost half of the world's population (Ricestat, 2018): around 500 million tons of processed rice are produced globally and about 90% of this production comes from Asian countries.
In fact, the moisture content of paddy rice after harvest is generally higher than 20%, while for its correct shelf life it is necessary to reduce it to 12-14%. After harvesting, the paddy rice should be dried as soon as possible: the ideal would be to proceed with the treatment within 24 hours, in order to avoid the onset of mold, but also the germination of the product, with consequent losses. In fact, the drying of wet paddy rice carried out in a non-optimal way is responsible for the loss of quality of the cereal and the increase in economic losses.
In this article, Mecmar explains how a correct rice drying process allows to reduce post-harvest losses by minimizing the microbial activity and respiration of the cereal.
Rice: characteristics and types
Rice is a hygroscopic material: it can absorb water molecules present in the environment. Therefore, if it is exposed to air with higher humidity than that of rice grains, they will absorb the water present in the air by increasing their internal moisture; otherwise, if the wet rice is exposed to an air with low humidity compared to that of the rice grains, these will release water into the air.
For proper storage of the rice, it is essential to provide for a drying phase and, if possible, also a cleaning phase of the grains, to allow a uniform drying, free from moisture stains. To obtain optimal drying, it is necessary to accurately determine the temperature of the humidity of the air that will surround the grains, to prevent the humidity of the grain from increasing with a consequent deterioration in the quality of the seed.
Before being consumed for human nutrition, rice needs to be appropriately filtered and bleached, through a process of undressing the rice that removes its husks and husks.
There are different varieties of rice on the market, each with specific characteristics (for example, Vialone Nano, Arborio, Indica, etc.) characterized by different shapes and sizes.
The rice drying process
The market value of rice is determined by its quality, which generally reaches its peak immediately after harvest. The final quality of the rice is determined by the post-harvest processes; therefore, it is essential that the drying and storage process are properly calibrated to avoid a loss of moisture too fast and not to cause unwanted cracks or breaks in the carossides, or to cause decay of the product due to inadequate cooling and ventilation systems.
Drying and storage have the power to increase the efficiency of the rice starting from the possibility of reducing delays in harvesting and monitoring the quality of the grain. Moreover, it is essential to dry the grains within 12-24 hours from the harvest to reduce the risk of losses due to quality loss.
There are several methods for drying rice. Depending on the region, available technologies, and even local traditions, from Africa to Asia through Europe there are different alternatives, including:
- Rice lying in the sun,
- Forced air perforated beds,
- Column dryers,
- Recirculating dryers.
To carry out a correct drying of the rice without incurring unpleasant risks that could ruin the harvest, Mecmar proposes the drying of rice with its own mobile grain dryers and tower dryers. With Mecmar dryers it is possible to reduce drying times, speeding up the cereal processing phase and making it suitable for subsequent treatments or storage. All dryers are equipped with perforated sheets with 1.5 mm holes and with the "rice kit", consisting of a series of technical features, carefully designed and aimed at optimizing drying.
The drying of rice is a particularly delicate process and typically longer than the drying of other products: in fact, the air used to dry the rice must not exceed the temperature of 40-45 °C, since a higher drying temperature it could damage the grain. The technical precautions achieved after years of development allow to caress the grain and achieve a gentle and homogeneous drying of the whole product.
Thanks to the high performance of Mecmar mobile dryers it is possible to dry small and large quantities of rice. Furthermore, the flexibility and ease of transport that characterizes them makes them particularly suitable both for small farms and for larger ones that need to dry discontinuously and according to certain seasons.
Tower dryers, on the other hand, meet high drying requirements for hourly production and quantity of product to treat. Thanks to the continuous cycle operation, the rice is perfectly deprived of moisture without damage caused by thermal changes and, by specific inverters of the flow of the grain wall, a high homogeneity of the treatment is guaranteed.
The BIO line is perfectly suited to the delicate drying of rice for human nutrition: thanks to an innovative heat exchanger, which can be applied to both mobile and tower dryers, only clean air is used during drying, while the combustion products are conveyed into the atmosphere without coming into contact with the product. The resulting product is a homogeneous cereal, cleaned of external impurities and dried in accordance with the criteria of organic production.
Mecmar dryers are distinguished by high quality components, reliability and durability and ensure optimal, homogeneous, and delicate drying of any quality of paddy. Knowing that you can rely on precise machinery built around the real conservation needs of the grain, allows you to work safely and with the peace of mind that your harvest will not lose its quality and market value. If you want to know more about rice drying technologies, do not hesitate to contact us: the Mecmar team will be ready to answer all your questions and doubts.