The best way to measure the moisture of nuts in the laboratory

In this article, we review the best way to measure the moisture content of nuts in the laboratory. Nuts are one of the best foods and snacks that have many benefits for the body because of containing their nutrients, vitamins, minerals, omega 3, protein, fiber, useful metals such as calcium and potassium, and antioxidants.

The moisture content of dried fruits and nuts such as pistachios, pistachio kernels, almonds, hazelnuts, walnuts, walnut kernels, and seeds such as sunflower seeds are measured using the method introduced in this article.

This method is like determine the moisture content of dried fruits with this difference that the oven temperature and storage time in the oven and the size of the samples are different.

Moisture removal of nuts is one of the most important factors in its quality. Standard 672 of Iran Standards Organization, AOAC 22.013, and ISO 665: 2000 have been used to identify these methods to measure the moisture content in nuts.

This method is suitable to measure moisture in nuts and dried kernels such as pistachios, pistachio kernels, almonds, hazelnuts, walnuts, walnut kernels, and seeds such as sunflower and coconut kernels.

Required laboratory supplies for determination of nuts moisture:

• Laboratory scales with an accuracy of 0.001 g
• Oven with adjustable constant temperature 103 ±2 °C
• Platinum, porcelain, or silica plate with a containing capacity of 2 g/cm³ of the sample with a height of 5 mm
• Mill
• Desiccator
• Spatula
• Sieve with 3 mm mesh

Test method

Put the plate and its lid in the oven at 103±2 °C for 1 hour, then place it in the desiccator for half an hour to reach room temperature. Then weigh it (M₀)

Weigh 100 g of the skinless samples such as kernels and 200 g for skinned samples such as Pistachios or hazelnuts. Then grind them and pass them through a sieve so that the particle size is not bigger than 3 mm.

The temperature should be constant during the sieving time so as not to reduce the moisture in the nuts.

Now take 10 g of nuts without inner skin such as sunflower seeds and small nuts and 15 g of nuts with inner skin as the test samples. Pour the sample into a plate and close the lid so that it does not absorb moisture from the environment and weigh. Write down this weight (M₁).

Remove the lid of the plate to let the moisture leave it during evaporation when placing the plate in the oven. The sample should be placed in an oven at 103±2 °C for 3 h. put the plate lid on it after taking it out from the oven and immediately put it in the desiccator. When the sample reached the ambient temperature, weigh it, and write down the weight (M₂).

Repeat the test to increase the measurement test accuracy. The test is repeated as long as the weight difference between the two measurements is not equal to or less than 0.0005 g.

Remember- never put the wet and dried samples in the same oven together. The metal or glass plates can also be used but must be resistant to this temperature.

The amount of moisture in dried fruit is calculated according to the following formula and the result is expressed as a percentage:

Ref:

1. The health benefits of nuts
2. DETERMINATION OF THE MOISTURE CONTENT FOR NUTS