Canadian Grain Commission
Symbol of the Government of Canada

Measuring barley kernel colour and size to predict end use malt quality



Introduction

The grading system of the Canadian Grain Commission relies on a combination of visual and objective assessments to segregate malting barley into grades of different end use value. The effectiveness of the segregation system is not well documented as relationships between grades and processing, or malting potential, are not well understood. The importance of predicting malting barley potential will increase in importance as the Canadian malting barley industry strives to increase the malting barley pool by selecting barley of more mediocre and controversial quality. Therefore, Industry Services and the Grain Research Laboratory, both of Canadian Grain Commission, initiated a program to investigate relationships between barley assessment factors and malting quality. Visual appearance, or kernel colour, and kernel size were identified as primary factors requiring immediate attention.

Visual appearance is accounted for in Canadian Grain Commission grades by degree of soundness which is based on kernel maturity, weather staining and overall discoloration. The degree of soundness of a sample is established through visual comparisons with grade standards. Standards, representing the minimum quality for each grade, are assembled every crop year and are dependent on the dominant degrading factors for that particular harvest. Degree of soundness is expressed as standard verbal descriptions which are specific for individual grades. The official wording for the grades is as follows; "Reasonably sound, fairly well matured, may be moderately weather stained, but not seriously discoloured" for Special Select; "Fairly sound, may be slightly immature and moderately weather stained or discoloured" for Select; and "Excluded from other grades of malting quality barley on account of weather staining or discolouration" for Standard Select. The relationship of grain soundness to malting quality is not well documented. The present study investigated the malting quality of a series of samples with varying degrees of soundness. Malt quality was also compared to more objective colour values as assessed with image analysis or a visual colour scale.

Kernel size is another important grade determinant. Malting barley grades have minimum levels for percentage of plump kernels, and test weight, as well as maximum levels for percentage of thin kernels. In addition, export certificates often require 1000 kernel weight as a measurement of kernel size. Standard tests for measuring kernel size are generally more objective than degree of soundness, however, the value of the sizing results for predicting end use quality is often questioned. In the present study, malt quality of a series of samples was compared to kernel size as determined by 1000 kernel weight as well as with the SKCS. SKCS measures and calculates means and standard deviations of the weight, diameter, moisture and hardness of 300 individual kernels from each sample tested.