GB 18394-2020Permitted level of moisture in meat of livestock and poultry (English PDF)

5.1.4 Sample preparation

5.1.4.1 Sample collection Make an incision from the sampling site, avoiding fat, sinews, and tendons. Cut about 200 g of muscle. Place in an airtight container. Cooling meat should remove any surface air-dried parts. Frozen meat should be sampled from within the sample.

5.1.4.2 Sample processing 5.1.4.2.1 Non-frozen samples Fat, sinews, and tendons should be removed from the sample before testing. Take the muscle part and homogenize it. Homogenized samples should be tested as soon as possible. If it cannot be detected in time after homogenization, it should be stored sealed and refrigerated. Sealed and refrigerated storage time should not exceed 24 h. Stored samples should be remixed during testing. 5.1.4.2.2 Frozen samples Thaw at 15°C~25°C. Record the sample mass m3 and m4 before and after thawing (accurate to

0.01 g). Thawed samples are processed according to 5.1.4.2.1.

5.1.5 Analysis steps

5.1.5.1 Constant weight of weighing vessel: Put a thin glass rod and about 10 g of sand into the weighing vessel. Place it into a constant temperature drying oven at (103±2)°C and maintain a constant weight. Record the mass after constant weight (m0).

5.1.5.2 Weigh about 5 g of sample (accurate to 0.0001

g) and place it in a weighing vessel. Accurately record the total mass (m1) of the sample and weighing vessel. Use a fine glass rod to mix the sand and sample evenly.

5.1.5.3 Move the weighing vessel and sample to a constant temperature drying oven at (103±2)°C. After drying for 4 h, take it out and cool it in a desiccator before weighing. Dry it again in a constant temperature drying oven for 1 h, take it out, cool it and weigh it. Repeat the above steps until the mass difference between two consecutive times is less than 2 mg. Record the total mass of the final weighing vessel and contents (m2).

5.2 Infrared drying method (quick method)

5.2.1 Principle Use infrared heating to remove moisture from the sample, and then use the mass difference before and after drying to calculate the moisture content.

5.2.2 Instruments Infrared rapid moisture analyzer: the moisture measurement range is 0%~100%. The reading accuracy is 0.01%. The weighing range is 0 g~30 g. The weighing accuracy is 1 mg.

5.2.3 Determination

5.2.3.1 Turn on the power and turn on the switch. Set the drying heating temperature to 105°C and the heating time to automatic. The result is expressed in the range of 0%~100%.

5.2.3.2 Open the sample chamber cover. Take a sample pan and place it on the balance frame of the infrared moisture analyzer, and return it to zero.

5.2.3.3 Take out the sample pan. Spread approximately 5 g of the sample prepared according to

5.1.4.1 evenly on the plate. Put it back into the sample room.

5.2.3.4 Cover the sample chamber cover. Start heating. After drying is complete, read the moisture content on the digital display. When equipped with a printer, the moisture content can be automatically printed.