Two elements make up grain:
- Dry matter (DM): this includes starch, proteins, lipids, and fibre.
- Water (H₂O): this is the variable water fraction that determines the moisture content.
Weight equation:
Total weight = Dry matter weight + Water weight
Example: 100 kg of corn grain with 15% moisture content contains:
- 85 kg of dry matter
- 15 kg of water
The effect of moisture content on weight
The market does not pay for water content, only for dry matter. Therefore, two batches containing the same amount of dry matter but with different moisture contents will have different weights. This means they will have different commercial values.
- Batch A: 100 kg at 15% → 85 kg of dry matter.
- Batch B: 100 kg at 17% → 83 kg of dry matter.
Visually, the gross weight appears to be the same, but the actual dry matter value is lower in batch B. The buyer therefore adjusts the price using a shrinkage factor.
The effect of moisture content on volume
One hectoliter of first-quality corn at 14.5% moisture content weighs approximately 72 kg. The more moisture the grain contains, the lower the weight per hectoliter, because water is lighter than cornstarch.
Thus:
- Corn at 13.5% → approximately 73.5 kg/hL
- Corn at 14.5% → 72 kg/hL (reference)
- Corn at 17% → approximately 70 kg/hL
Quite rightly, when corn is dried, it gains weight. This means that #3 grade corn may be reclassified as #2 grade due to the increase in density during the drying process.
But be careful! A grain that has not reached full maturity may lose weight, especially if it is heated to a high temperature.
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