Microbiological & Keeping Qualities of Rice

Metal Bin Storage

• Different temperatures in stored rice cause moisture to move within the rice. The problem is greater if you store your rice in metal bins. Stored rice is usually warmer than the outside air in the late fall and early winter. Warm air rising slowly from the center of the rice cools when it hits the cold air at the top of the bin. The relative humidity increases and the top of your rice will gain moisture, which is an invitation to fungal microbes.

Flat Bin Storeage

• Dips and peaks in your rice will restrict the air flow. Keep your rice level. If you store your rice in a flat bin, use fans to maintain an airflow of at least .2 cubic feet per minute (cfm) for every hundred pounds of rice (cwt). This will cause cooling or warming air to move through your rice every 100 to 200 hours. If your airflow is .1 cfm, run your fans 200 to 240 hours for each cwt.

Fans

• Run your fans in the fall when the air temperature is cooler than the rice and in the spring when the air temperature is warmer than the rice. If you keep your rice cool in the winter, warm it in the spring. If you control your aeration fans manually, run them two or three times a week or when then relative humidity outside is between 55 to 70 percent. If the humidity drops below that range, your rice will dry out; if it is above that, your rice will gain moisture, inviting fungal microbes. You can buy an aeration controller that will stop and start fans depending on the relative humidity and air temperature.

Rice Moisture Level

• Your rice should contain less than 12.5 percent moisture in the summer. If you keep your rice at 14 percent moisture in the winter, it will remain below the recommended 65 percent humidity. If you add 7 to 8 degrees F of heat to cold, foggy air, you will reduce the relative humidity from 100 percent to 75 percent. The best way to check the moisture levels of your rice is to use an electronic humidity probe to measure the humidity of the air within your bin. Some probes will give you a humidity reading in about five minutes.

Rice Inspection

• Inspect your rice weekly. Be alert for odors that suggest spoilage, the work of fungal microbes. Remove and dry wet rice. After you dry it, make sure it is free of mold before you mix it back with your good rice. If you have dependable, automated fans, you may not need to monitor grain temperature.