SOP: Determination of Moisture Content and Total Solids in Cereals and Pulses Flour
GIFSQ — Global Institute for Food Safety & Quality
1. Principle
The sample is heated at a specified temperature for a specified time in a hot air oven, and the loss in weight is taken as a measure of the moisture content of the sample. Total solids are obtained by difference from the moisture content.
2. Equipment required
- Calibrated electronic balance (±0.01 g)
- Calibrated hot air oven (temperature 100–130°C)
- Aluminum moisture dish with lid
- Tongs
- Airtight desiccator with dried silica crystal
- Calibrated thermometer
3. Procedure
Dry the aluminum dish with lid for half an hour in the oven at 130 ± 3°C
↓
Cool in a desiccator to room temperature
↓
Weigh the cooled aluminum dish
↓
Weigh about 2 g of well-mixed flour sample in the moisture dish
↓
Uncover the dish and dry the sample in the hot air oven at 130 ± 3°C for 1 hour, until constant weight
↓
Cover the dish with the lid while still in the oven, transfer to a desiccator, cool, and weigh the dish with the dried sample
4. Calculation
Percentage of free moisture = (Weight loss on drying ÷ Weight of sample taken) × 100
= [(Y − Z) ÷ (Y − X)] × 100
Where,
– X = weight of aluminum dish
– Y = weight of dish with sample
– Z = weight of dish with dried sample
Percentage total solids = 100 − % Moisture content
5. Precautions
- The drying period should start only when the temperature of the oven actually reaches 130°C.
- Spread the sample over the aluminum dish evenly.
- The cooling desiccator must contain effective desiccant.
- The hot air oven must have good temperature control, and the thermometer should be well calibrated.
6. Limit of detection
This method gives the amount of free moisture, but does not give the total water present in the sample. (Section heading and note as printed in the source.)
References
AOAC, 21st edition, 2019; Official Method 925.10.