Method for Determining the Moisture Content of National Reserve Rice

Based on Section 3.2.2, Part 3, National Technical Regulation QCVN 06:2019/BTC promulgated together with Circular 78/2019/TT-BTC stipulating the method for determining the moisture content of national reserve rice as follows:

Determination of Moisture Content: Conducted according to ISO 712: 2009 Cereals and cereal products - Determination of moisture content - Routine reference method or other methods that yield results with equivalent or higher accuracy can be used.

Tools and Equipment

- Analytical balance, accurate to ± 0.001 g.

- Metal or glass weighing cup with a tight cover.

- Drying oven, with temperature control between 130°C to 133°C.

- Desiccator.

- Grinder, with the following characteristics:

+ Made from non-hygroscopic material;

+ Easy to clean, with capacity suitable for the sample size;

+ Capable of quick grinding and producing uniform particle size without significant heat generation and airtight (no external air contact);

+ Adjustable to ensure all ground particles pass through a 1.7 mm x 1.7 mm mesh sieve.

Procedure

Adjust the grinder to ensure all ground particles pass through a 1.7 mm x 1.7 mm mesh sieve. Grind a small sample and discard it. Then quickly grind and immediately weigh approximately 5 g of the test sample. Weigh the ground sample with an accuracy of 0.001 g. Place it in the weighing cup with a lid (the weighing cup and lid should be pre-dried to a constant weight and weighed with accuracy to 0.001 g). Open the weighing cup lid and place the cup in the drying oven (place the lid next to it inside the oven). Dry the sample at a temperature between 130°C to 133°C for 120 minutes (± 5 minutes) from the time the oven reaches 130°C to 133°C.

Quickly remove the weighing cup from the oven, cover it, and place it in the desiccator. After 30 to 45 minutes, once the cup has cooled to room temperature, weigh it with an accuracy of 0.001 g.

The moisture content of the rice (W) is calculated as a percentage, determined by the formula:

Where:

m₁ is the sample weight before drying, in grams.

m₂ is the sample weight after drying, in grams.

The test result is the arithmetic mean of two parallel determinations on the same sample when their deviation does not exceed 1% of the mean value. Report the result to one decimal place.

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