Beans: protect the grains from mold during storage.

Post-harvest of bean Proper harvesting, threshing, drying, and storage require attention from the moment the plants are harvested from the field until the product is delivered to the market or processing unit. Inadequate harvesting, threshing, drying, and storage can lead to moldy grains, reduce quality, and compromise the commercial value of the production.

Mold growth is primarily the result of fungal action under favorable humidity and temperature conditions. Besides devaluing the product, deterioration can lead to the formation of mycotoxins, compromising food safety and the commercial acceptance of batches.

In virtually all bean-producing regions of Brazil, the challenge is to harvest the beans from the field with adequate moisture, achieve efficient drying, and maintain storage conditions that hinder the development of fungi.

The problem begins in the field. The harvest point, the time until drying, and the care taken during threshing directly affect the quality that will be maintained during storage.

Beans harvested with very high moisture content present a greater risk of overheating and fungal growth if not dried quickly. On the other hand, delaying harvesting increases exposure to rain, rehumidification, regrowth, and mechanical damage.

Insufficient drying is also among the main causes of deterioration. When the grain retains moisture above the level appropriate for the storage period, conditions increase for heating of the mass and development of fungi.

The process needs to be conducted with balance. Very slow drying in humid environments can prolong the grains' stay in conditions favorable to fungi. On the other hand, excessively high temperatures can cause thermal damage and cracking.

These damages are important because breaks, cracks, and fissures facilitate the penetration of fungi and accelerate deterioration during storage.

In mechanized harvesting, well-regulated equipment helps reduce the percentage of broken and husked grains. During threshing, adjustments to speed and plant intake flow also contribute to minimizing damage.

Pre-cleaning is another important point. Straw, pod fragments, soil, stones, and weeds increase local humidity, hinder air circulation, and can serve as a substrate for fungi.

Removing these impurities before drying improves the efficiency of the operation and helps reduce the formation of mold. Drying is considered one of the main steps in preserving the quality of beans. The faster the product reaches a safe storage condition, the shorter the period of exposure favorable to deterioration tends to be.

During natural drying, the grains should remain on clean, impermeable surfaces, such as paved patios, tarpaulins, or appropriate structures. Direct contact with the soil should be avoided to reduce the risk of contamination and moisture absorption.

The grains should be spread in a uniform and relatively thin layer, allowing for greater ventilation. Very thick layers retain moisture and promote the formation of mold spots.

Regular turning throughout the day also helps to even out drying and prevent localized heating. Another precaution is to protect the product from rain and dew. The beans should be moved to a covered area or protected with suitable tarpaulins when necessary, as rehumidification overnight promotes the development of fungi.

In artificial drying, it is necessary to use equipment suitable for small grains, following the manufacturer's recommendations and technical assistance. The air temperature needs to be controlled to avoid thermal damage, such as reduced germination, hardening of the grains, and cracking. In the case of seeds, even greater care is needed.

During the process, the moisture content of the grains must be monitored. Drying should be stopped when the appropriate level for the intended storage period is reached. Homogeneity of grain flow is also important in continuous or intermittent systems. The goal is to prevent part of the mass from becoming excessively dry while another part remains moist.

After drying, storage must maintain stable humidity and temperature conditions. Good practices are important for both bagged beans and the product stored in bulk. Before receiving the grains, the warehouse must be thoroughly cleaned. Residues from previous harvests, dust, broken grains, husks, and dirt accumulated on floors, walls, ceilings, and equipment can act as breeding grounds for fungi and insects.

The structure also needs to be inspected. Leaks in the roof, cracks, poorly sealed doors and windows, and points of water infiltration must be corrected to prevent water and moisture from entering.

Sacks should be stored on pallets or racks, never directly on the floor. It is also important to keep them away from walls to allow for air circulation and facilitate inspections. Ventilation and aeration, when available, help maintain the temperature of the grain mass at safer levels and reduce condensation points.

When storing goods in sacks, clean, dry packaging in good condition should be used. Stacks must be stable and have aisles for circulation between them and the walls. Very high stacks in hot, poorly ventilated warehouses should be avoided, as the central area can concentrate heat and humidity.

In bulk storage, grains must enter the silo or warehouse with adequate moisture content for the intended storage period. Aeration systems can be used to homogenize the temperature and prevent moisture migration and the formation of mold zones.

Regular monitoring of the mass is also necessary. Thermometers, probes, and moisture measurements at representative points help identify changes before the problem spreads.

Storage insects also need to be controlled. Weevils and moths, in addition to consuming the product, can produce heat and increase the respiration of the grain mass, creating favorable conditions for fungal growth.

Integrated pest management should combine cleaning, sealing of the warehouse, use of screens, monitoring with traps and, when necessary, chemical methods duly registered and recommended for beans. The use of unregistered products or products outside the label and package insert recommendations should be avoided. In addition to being illegal, this practice can leave non-compliant residues and does not solve the main cause of mold when it is related to high humidity.

During storage, visual inspections should be carried out periodically. Whitish, greenish, or blackened spots, a musty odor, stuck grains, and crust formation may indicate spoilage. Hot spots in the dough also deserve attention, as they may indicate fungal growth or insect infestation.

Whenever possible, samples should be collected from different points in the batch to check for moisture, especially when rehumidification caused by leaks or condensation is suspected.

Rotating inventory also helps avoid unnecessarily long storage periods. The recommendation is to use a first-in, first-out (FIFO) principle. The economic impact of mold can be significant. Fungi consume dry matter and can reduce the weight and commercial yield of grains.

Discoloration and the appearance of blemishes also reduce the value of the product. In types of beans where appearance directly influences the price, such as carioca and black beans, the impact can be even more significant.

Deterioration can also affect cooking power. Damaged grains tend to require longer cooking times, become hard, and have altered flavors, negatively impacting consumer acceptance.

Another point of concern is the risk of mycotoxins. Some fungi can produce substances such as aflatoxins and ochratoxins. At high levels, these substances can pose a risk to human and animal health and also contribute to the rejection of batches by the industry and institutional purchasing programs. For seed producers, the damage can also compromise germination, vigor, and the health of the material, affecting the performance of future crops.

Prevention, therefore, needs to integrate field and post-harvest practices. A well-nourished crop, with adequate control of late-cycle diseases and proper irrigation management, tends to produce healthier grains with less incidence of damage that facilitates the entry of fungi.

The choice of cultivars can also contribute. When available, materials with better pod and grain health and an architecture that facilitates harvesting can reduce the product's exposure to moisture and pathogens in the field.

Planning the planting season is another component of the system. Organizing crop establishment so that harvesting occurs during periods with a lower probability of heavy rainfall facilitates natural drying and reduces the risk of harvesting grains with high moisture content. To increase autonomy and ensure quality, post-harvest infrastructure also needs to be considered. Drying areas, artificial drying equipment, storage structures, and cleaning and sorting systems are important investments for the producer.

Worker safety cannot be overlooked. Post-harvest operations involve risks related to dust, noise, moving machine parts, and working at heights in silos.

Appropriate personal protective equipment should be used according to the activity, including dust masks, goggles, gloves, ear protectors, and appropriate footwear.

Dryers, elevators, conveyors, and other equipment must follow usage recommendations and undergo preventive maintenance. In addition to reducing accidents, maintenance helps prevent malfunctions that could compromise grain quality.

When pesticides or fumigants are needed in warehouses, it is necessary to strictly follow the legislation, the label, the package insert, the agronomic prescription, and the safety standards, as these products require specific training and proper application and re-entry procedures.

The involvement of agricultural engineers and other qualified professionals is recommended for sizing structures, defining drying and storage strategies, and guiding integrated pest management. The main strategy to prevent moldy beans is to prevent moisture, favorable temperature, and exposure time from creating conditions for fungal growth.

In practice, this means harvesting at the right time, reducing the drying time, cleaning the grains, conducting the drying process correctly, preparing the storage area, controlling insects, and continuously monitoring the temperature, humidity, and appearance of the product. With these integrated practices, the producer reduces quality losses and increases the chances of preserving the commercial value and safety of the beans throughout the storage period.