SATAKE CORPORATION UK DIVISION
COLOUR GRADER PCGA FEATURE ARTICLE

COLOUR IS THE KEY

Despite the nutritionists’ declarations that wholewheat bread is better for our health, the white bright loaf remains top of the consumer’s shopping list.

In this article, we explain the advantages of colour grading as a measurement of flour quality and describes the features of the widely-accepted Colour Grader PCGA.

Quality and consistency  -  two key routes to profitability for millers and bakers.

The consumer expects the loaf bought today to be identical to the one bought yesterday and the one bought the day before that.  Our consumer also expects the cost of the loaf to remain as low as possible and so, in order to make a profit, the baker must operate efficiently, paying particular attention to his costs.

With his eye fixed firmly on quality and consistency, the baker wants to be able to buy flour wherever and whenever he needs it.  He is increasingly anxious to purchase on a Just in Time basis, so that he does not need to carry large stocks and so he will always be using “new” flours.  He wants this flexibility but he does not want to be constantly adjusting his recipes and baking procedures to cater for variations in the flours’ properties.

The miller want to protect his profitability by achieving the maximum extraction of flour from the wheat he buys.  But he must not sacrifice the quality and consistency of the flour or he will not satisfy his customer – the baker.
Quality and consistency are both measurable, two of the recognised criteria for flour quality are ash and flour colour grade.

Reliable

In   countries such as Britain, where mineral matter in the form of calcium, carbonate has long been added to flour for nutritional reasons, ash measurement has, many years ago, been discredited and discontinued as a routine test.

Even in countries with rigorous ash regimes, we have become aware of a change in attitude to flour quality criteria, with more interest in flour colour as a reliable means of quality measurement and prediction.

Ash content has to-date been usable as a measure of the baking quality of flour on the basis that it gives an indication of the bran contamination.  However, a slow change is taking place to give more emphasis to flour colour and image analysis.  With the introduction of effective debranning systems, we at Satake UK foresee an acceleration in this trend.

Bread baked from flour milled using a debranning process has a better volume and a brighter colour, despite sometimes having a higher than expected ash content.  Therefore, as only minimal bran is likely to be present in flour pre-processed in a debranning system, a typical ash content analysis would give a quite misleading measure of the baking quality of the flour.

Universally Accepted

Colour determination involves making a measurement on a calibrated scale by comparing a sample of flour from the mill against another flour sample or a ceramic tile of a known  colour value.  It is a measurement of deviation-from-a-known .  The procedure is an essential element of milling flour for breadmaking, because flour colour affects bread colour and, more importantly, because it gives an indication of the product’s breadmaking quality. 

In 1950, the Kent Jones and Martin Laboratories launched their Flour Colour Grader, an instrument which was an immediate success with British and Irish Millers, and which has since become universally accepted.

Various alternative instruments have been developed in the intervening years – in particular, the Agtron Tristimulus is used in North America whilst Minolta or Dr Lange Tristimulus meters are used in Australia.
Most recently, video/computer techniques involving image analysis of the size and number of bran particles present in a sample have been developed.

The results of image analysis can be used to complement the colour measurement.

Meanwhile, the original Kent Jones and Martin instrument has been developed through four generations.  It is still the forerunner in providing quality assurance managers with an accurate and reliable indication of colour and hence the quality and consistency of flour.

Automated

The Series 4 instrument, the automated Colour Grader PCGA now available from Satake UK, was design following the closure of the Kent Jones & Martin Laboratory, taking into account the findings of market research which, especially in Japan, placed particular emphasis on the use of improved technology and user-friendly methods of operation.

The Colour Grader PCGA Series 4 uses state-of-the-art electronics and microprocessor controls with reliable modern power supplies.  The human interface features simple, rugged digital display and printout facilities.   The flour grade is displayed via 15 mm LED’s and simultaneously printed with the time and date on the integral printer.
The instrument has a linear light path and uses better lamps than previous models, with stable illumination.  The optics have been improved, with an integrating sphere detection system of the same type as those used in NIR (Near InfraRed) analysers.  Since product particle size affects the reflectance of light from a surface, the flour must be mixed to a paste with water before measurement to eliminate any discrepancy caused by uneven particle sizes.

The light source is a halogen lamp with a long life expectancy and uniform illuminating power right up to final failure.  In order to ensure both short and long term stability, the measurement of reflectance from the measured surface is continuously compensated by correcting for any variation in lamp intensity using separate optical sensors, and by automatic reference to an Internal Standard a few seconds prior to each measurement of the sample.

                                                  
The value C is the colour of the Internal Standard and this is obtained by careful standardisation with a flour of known colour grade.

Earlier instruments in use up to 1980 required a white tile or Ultimate Internal Standard to be immersed in a specific liquid inside the colour grade sample cell.

However, this liquid, called monochlorobenzene, was found to present a health hazard.    Henry Simon Ltd, who then marketed the Kent Jones and Martin Colour graders, decided to stop the supply of UIS for these health reasons and advised all customers of the calibration and standardisation procedure using Standard Flour.

Adendum (author Satake UK)

Satake UK measures the values for the standard flour using a Standard Series 3 Colour Grader and now the newer Tristumulus instrument the NCG1a, which in turn is kept in calibration using “Linearity Testing Instrumentation”, as always used since 1954, its dedicated Ultimate Internal Standard and the National Standard flour as supplied to the UK industry.

Ash Determination – A Useful Standard or a Flash in the Pan?
A.D. Evers, Ascus Ltd.,
M. Kelfkens, TNO Nutrition and Food Research,
G. McMaster, BRI Australia Ltd.