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EBC Method 4.7.2 Colour of Malt: Visual Method — Yellow Spot Colour Discs
Author(s) -
Sole S.M.,
Johnson B.A.,
Griggs D.L.,
Gibbs J.,
White D.
Publication year - 2005
Publication title -
journal of the institute of brewing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.523
H-Index - 51
eISSN - 2050-0416
pISSN - 0046-9750
DOI - 10.1002/j.2050-0416.2005.tb00676.x
Subject(s) - white (mutation) , citation , white paper , product (mathematics) , information retrieval , computer science , library science , chemistry , mathematics , political science , law , biochemistry , geometry , gene
In January 2005 the Crisp Malting Group Central Laboratories compared a new 3-field colour comparator and discs, on loan from The Tintometer Ltd, with their current Tintometer equipment prior to its being serviced and recertified by the manufacturer. Investigations showed differences between the two sets of yellow spot colour discs. Contact with The Tintometer Ltd revealed that in December 1999, Tintometer’s colour laboratory became certified to ISO/IEC 17025:2000 as a traceable colour calibration facility. In October 2002 (10/02) the approved master set of EBC yellow spot discs was realigned to the reference CIE (Illuminant B) chromaticity co-ordinates published in 1997 in ANALYTICA-EBC. Changes to the discs were small and notification to the brewing and malting industries was considered unnecessary. The net effect, however, was to create two slightly differing standards within the yellow spot coding of the discs, viz: pre 10/02 and post 10/02. A co-operative assessment involving Crisp Malting Group, Greencore Malt and The Tintometer Ltd examined a range of beers and laboratory worts. Colours were determined by five analysts using new 2-field and 3-field comparators with new preand post 10/02 disc sets. Spectrophotometric readings were also obtained. Paired t-tests were carried out on the 2-field and 3-field comparator data. In both cases, significant differences at the 95% confidence level were detected between pre 10/02 and post 10/02 disc sets. No significant difference was found between 2-field and 3-field comparators. Data from both sets of discs were found to be statistically different to the spectrophotometer data, although the post 10/02 discs were a closer match. Analysis of variance showed that there was no significant difference between the analysts involved in the experiment. The relationships between colour from the two sets of discs and spectrophotometric colour were found to diverge as colour increased (see Table I). The differences in the disc readings, although apparently small, could have a significant commercial impact in the trading of beer and malt, and particularly for suppliers of speciality malts to brewers. It is possible that the values for colour reported by laboratories using pre 10/02 or post 10/02 yellow spot disc sets could result in product being dispatched within specification by a supplier but being rejected on evaluation by a customer. A full report is to be submitted for publication.