Grain Storage: Considerations to Maintain Quality: Part 2 - Moisture Temperature Storage Capability,

Moisture Temperature Storage Capability

On the left side of this chart (Figure 1) is temperature, and at the bottom is moisture (as a percent of content in whole grain). By reducing the available moisture in grain, the growth opportunity for mold and fungi decreases dramatically. Reducing temperature also contributes to the reduction of mold and fungi growth.

Reducing moisture has less effect on insects, but grain temperatures below 22 ºC decrease insect life activity (without consideration of moisture content). Temperatures below 18 ºC stop most insect life cycle activity. In tropical climates this can be achieved only with mechanical refrigeration, which has proven very effective.

Safe Storage Period (Days - Corn/Maize)

Moisture content and temperature within a stored grain mass have a direct impact upon the number of days that grain can be stored. The worst-case example on this table, grain with a temperature of 27 ºC and 30% moisture content can only be stored for 2.6 days before the grain is spoiled. By reducing the moisture content to15%, the total number of possible storage days increases to 87 at 27 ºC. At the same time if the temperature were reduced to16 ºC. the available storage days will rise to 250. The day count begins at the time of harvest not the day that the grain is placed in storage. Lost available storage days can never be recovered. If half of the storage life of grain is lost while the grain is at high temperature or high moisture, those days cannot be restored. Therefore it is important to reduce grain moisture content and temperature as quickly as possible after harvesting.

Safe Storage Period (Days) Temperature & Moisture (Corn)

By examining the safe storage day information in a graph, it becomes apparent how critical the reduction of moisture and temperature become. Notice that grain stored at 13% moisture can be stored in excess of 4000 days at a temperature of 4 ºC. On the next slide, we will examine in greater detail the Safe Storage Days in the more common range of 16 ° to 27 c. and moisture content of 13% to 20%.

By reducing the moisture content to 15%, Safe Storage Days increases to between 100 and 250 days depending upon the temperature of the grain. Managers must determine how dry the grain should be, by deciding how long the grain will be stored before use. Remember that the number of days the grain has been stored before you purchase it will affect the total Safe Storage Days.

When To Aerate Grain?

Because moisture and heat can accumulate in hot spots within the grain mass, aeration should be initiated to distribute or remove concentrations of heat and moisture. Accumulations of moisture cannot be detected, but the rise of temperature associated with moisture and spoilage can be detected with temperature detection systems.

Aeration should be initiated on a regular schedule of preventative maintenance in order to equalize the moisture and temperature within the grain mass. The temperature of the grain mass should be maintained equal to the temperature of the outside air. Because temperature differences greater than 9 ºC between the air and the grain mass can create condensation and moisture in the grain, aeration should only begin when the difference between the grain and the outside temperature is less than 9 ºC. A regular schedule of aeration maintenance will keep the grain close to the average outside temperature.

The aeration objective is to maintain the grain at a uniform temperature of +/- 2 degrees of the average 30-day daily temperature.