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PT_BR 
Cleaning the grains bean Post-harvest handling is an important step in preserving quality and reducing risks during storage. Removing straw, stones, clods, seeds from other plants, and damaged grains helps to decrease the presence of fungi, insects, and weight loss, as well as contributing to maintaining the commercial standard of the product.
After harvesting, beans typically arrive at the processing plant mixed with fragments of pods, stems, soil, stones, weed seeds, and broken, green, immature, or blemished beans. This material can increase the moisture content of the bean mass, encourage the presence of pests, and raise drying and handling costs.
Cleaning also becomes important when harvesting and threshing occur under varying moisture conditions. During rainier periods, the amount of impurities and damaged grains tends to increase, requiring greater attention before the product is sent to storage.
The process generally begins with the reception and inspection of the grains. At this stage, the moisture content, the level of impurities, and the presence of visible insects or fungi are evaluated. The color, shine, and the occurrence of green, stained, or moldy grains are also checked.
Based on this information, the producer or person responsible for processing can determine the drying needs and the type of cleaning required. Typically, the beans should have an adequate moisture content, around 13%, for the process to be carried out efficiently.
Pre-cleaning is the first step in the separation process. Sieves or specific machines remove larger materials, such as straw, pod pieces, stems, and clods, as well as finer particles like dust and loose soil.
When the system has air suction, dry leaves, light straw, and dust can also be removed due to the difference in density. Adjusting the inclination, feed flow rate, and air intensity is necessary to prevent good grains from being eliminated along with the impurities.
If the beans arrive at the processing plant with a moisture content higher than recommended for storage, drying becomes necessary. The process can be natural, on a drying patio, or artificial, using dryers with heated air or forced natural air.
The temperature and drying time must be adjusted to avoid cracking and other defects in the grains. After the operation, the moisture content needs to be checked again and, if necessary, the product can return to the cleaning stage.
In cleaning and sorting using sieves, different mesh sizes are used to separate grains according to size and remove unwanted particles. Larger sieves can retain very large grains and foreign materials, while smaller sieves allow the removal of small, broken grains and fine impurities.
The adjustment should take into account the type of bean and the average grain size of the cultivar. An inadequate setting can lead to losses of marketable product or allow unwanted materials to remain in the batch.
Ventilation complements the work of the sieves. A controlled airflow passes through the grain stream and removes light particles, such as loose husks, dust, and straw fragments.
The air velocity needs to be calibrated. When it is insufficient, light impurities are not removed properly. If it is excessive, it can carry away good grains and increase losses.
When available, density sorting can further improve batch quality. Density or gravity sorting tables allow for the separation of full grains, with higher specific gravity, from those that are shriveled, damaged by insects, moldy, or partially deteriorated.
In units with more advanced equipment, optical sorters can also identify grains with different colors or external defects and separate them from those that meet the standard. In simpler systems, manual sorting can complement the process, especially in higher value-added batches.
Before the beans are sent to the silo, warehouse, or bagging area, it is recommended to carry out a new sampling. The evaluation should verify the moisture content, the percentage of residual impurities, the number of broken grains, and the presence of seeds of other species.
Proper cleaning helps reduce the risk of fungi and mycotoxins because it removes impurities and grains that are already damaged. Removing straw and broken grains also reduces the availability of shelter and food for storage insects, such as weevils and moths, as well as mites.
Another effect is related to commercial quality. A batch with fewer broken, stained, and foreign materials can achieve better grading and meet more demanding marketing standards.
Cleanliness also affects the efficiency of drying and aeration. Masses with a large amount of impurities hinder airflow, while clean grains allow for better circulation and facilitate preservation operations.
The timing and intensity of cleaning depend on the characteristics of each batch. The moisture content upon receipt is one of the main criteria, as well as the quantity and type of impurities present.
Plots with a lot of soil, stones, and plant debris may require more intensive pre-cleaning or more than one pass through the sieves. The type of harvest and threshing conditions also influence the result, since well-regulated operations tend to generate fewer broken grains and a smaller quantity of impurities.
The weather is another factor to consider. During rainy periods, prioritizing cleaning immediately after receiving the beans helps reduce the time they remain in contact with impurities and high moisture content.
The intended use of the product should also be considered. Beans destined for more demanding markets or higher-quality industrial processes may undergo additional selection steps and require a more rigorous cleaning standard.
To avoid losses, the process should begin with organized reception and representative sampling of the cargo. Collecting samples at different points allows for a better assessment of moisture and impurities, guiding subsequent steps.
Pre-cleaning should be carried out as quickly as possible, removing straw, larger stones, and excess dust. Then, when necessary, the product should be dried, with constant monitoring of the moisture content.
Subsequently, fine cleaning should be carried out using properly adjusted sieves, with feed flow control to avoid overloading the equipment. When available, a densimetric table can complement the separation of light, shriveled, or damaged grains.
After all operations, a new sampling allows for verification of the achieved quality. If there is still an excess of impurities, further adjustments or another pass through the cleaning system may be necessary.
Only after this inspection should the beans be sent to storage. Silos, grain warehouses, and sacks must be in suitable conditions, with a dry and well-ventilated environment and pest control.
Cleaning, however, should not be treated as an isolated operation. The result also depends on the harvest point, the quality of the threshing, and the drying process. Harvesting at the right time reduces the amount of green and damaged grains, while correct machine settings decrease breakage and impurities.
Removing impurities before drying can also improve process efficiency, while storing clean grains facilitates air circulation and control of the stored mass's conditions.
Excessive vibration or impact from equipment can cause further breakdowns, while poorly adjusted sieves can remove good grains along with impurities or allow unwanted materials to remain.
The same care should be taken with vacuuming. A very strong airflow can remove marketable grains, increasing quantitative losses. On the other hand, insufficient cleaning compromises subsequent steps and increases the risk of problems during storage.
Therefore, post-harvest bean cleaning must be planned according to moisture content, impurities, harvesting system, and the intended use of the product. The combination of pre-cleaning, drying, sorting, vacuuming, and, when available, density sorting or optical selection contributes to delivering a cleaner, more uniform batch suitable for storage.
