Grain moisture determination: Influence of the mill type and implementation of the standard addition method in the trueness estimation

Olena Shcherbakova, SE “Ukrmetrteststandart”, Kyiv, Ukraine (Lena_nau@ukr.net)
Serhii Kulyk, Se “ukrmetrteststandart”, Kyiv, Ukraine
Oleksandr Melnykov, Se “ukrmetrteststandart”, Kyiv, Ukraine

Grain moisture content is a critical factor for storage optimizing and establishing a fair price for grain. However, according to the data of inter-laboratory comparisons, the moisture determination results obtained by main Loss-of-Drying (LoD) methods (ISO 712, ISO 6540) in different agricultural laboratories differ significantly. Such difference indicates that even if the ISO 712 requirements are met in laboratory, the laboratory result may still contain a systematic error.  

The purpose of the study is to verify the result trueness of the common LoD method, primarily ISO 712, using the standard addition method (SAM).

It was found that the main factor affecting the trueness of the result is the type of mill used to grind a grain sample. Disc mill Perten LM 3310 provides wheat grinding without statistically significant moisture loss if the sample moisture is within 11 % - 16 % and oven Binder FD 56 is used. Average value of water additive recovery is 99,7 %, and bias (-0.3 %) is statistically unsignificant against the overall variability of the results. The standard uncertainty of moisture determination result is 0,05 %.

The use of an uncooled knife mill provided a water additive recovery of 96.9 %. Bias (3.1 %) is statistically significant.

Comparative study found that a statistically significant underestimation of the moisture determination results is observed in more than 90 % of cases of uncoiled knife mills. Underestimation varies within a wide range - from about 0,06 % to 0,7 %; on average, the result is underestimated by 0,27 %.

Proposed SAM-approach can be used when checking the trueness of the results of moisture determination in laboratories including ones engaged in the production of CRM.

 

Short Biography of Presenting Author

My name is Olena Ghermanivna Shcherbakova, I am a researcher.