Grain sampling and assessment: Sampling grain in lorries

Abstract

The aim of this project was to establish if there are any inherent problems with the sampling of grain for the determination of quality characteristics in lorries at the point of intake and to establish recommendations in the form of a protocol for the sampling of grain under these conditions.

Grain was sampled using automated systems (Samplex CS90) and manual spearing to see if the method of sampling influenced the grain quality measurements. A key part of the process was to assess the influence that the number of samples taken from each load had on the likely accuracy of the results. Samples were collected at 4 different locations; on two occasions 10 lorries were sampled and on two occasions 8 lorries were sampled.

At three locations CS90 samplers were used and 8 samples were withdrawn from each load and at the other location samples were taken manually with a multi-compartmented spear with 5 samples being taken from each lorry. A comparison of different ways of sample handling was obtained by comparing the individual results from the 8 samples against an analysis of samples withdrawn from a composite sample formed from 8 samples. The latter method reflects more accurately the procedure followed at most stores.

Results indicated that there were no statistically significant differences between results from the individual samples or from the composite samples. Monte Carlo simulation of the impacts of using 2, 3, 5 or 8 samples per load revealed that the greater the number of samples used the greater the reliability of the result and the more likely it was to represent the true mean of the load. It was noted that automatic sampling equipment can no longer sample the entire length of a trailer and this could cause problems with obtaining the ideal sample. Manual sampling also had severe limitations due to the lack of safe access for sampling of trailers.

A sampling protocol for lorries is presented which emphasises the need for 8 samples to be taken from each load in order to get a good representation of the quality of the entire load.

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