How to measure the colour of different beans

How to measure the colour of different beans

Measuring the colour of different beans

The amount of types and varieties of beans is vast and is in the region of thousands but all share similar appearance traits. If one was to look at a selection of beans of the same type collected together in a pile, they would notice that while it is obvious the beans were of the same type there is a slight variation in appearance. The varying colour may not be an issue to a certain degree but there will be tolerances regarding appearance that deem a bean acceptable or nonstandard and establishing and controlling these tolerances is what spectrophotometers excel at.

Being a natural food stuff, there is bound to be disparity from bean to bean. All types of bean, regardless of the requirement and the reason for processing the bean, can be analysed in the same way, through reflected colour measurements; all that is needed is the correct spectrophotometer.

If we look at a simple method, it is obvious how easy and beneficial colour measurement can be.

Instrument

Because of the variations in size, shape and colour of the beans, an instrument is needed that can create a detailed image of what the human eye sees whilst giving accurate scientific data and not becoming unstuck by the natural variations in samples. This is to say that any spectrophotometer used should be able to negate height or size differences whilst gathering data.

Number of measurements

As with the measurement of most things, the more data you have, the better idea of the quality of the product. With a sample of such variation like beans, the best way to organise the data taken would be to create an average. This average would best represent the batch as a whole and provide suitable tolerances that would allow for natural variation but inhibit the allowance of substandard products.

Size of sample

For taking average measurements, the sample presented should be of a suitable size that it provides a large enough surface area for measurements. The amount of sample available for testing is one of the factors when deciding how much sample can be spared for examination. An operator can either take a measurement, turn the sample to adjust it and take another measurement or replace the entire sample for more from the same batch.

Utilising the Results

When the results have been received by the instrument, the next point to think of is what to do with them and what the purpose of collecting data is. Is the data used simply for quality control, making sure the product remains consistent? Is the data being sent to different locations to make sure the company has consistent quality from factory to factory? Is the colour technology being used to look for ripeness and to check the quality of each batch being brought in for processing? There are so many applications for colour measurement that it can be put to whatever use a company deems necessary.

A suggested method

Below is a basic method of measuring the appearance to outline the points listed above. This is a general guide and any method would be tailored to suit an individual manufacturer and their processes.

The instrument used would be the versatile D25 NC Spectrophotometer that utilises infrared technology to take non-contact measurements of samples of irregular sizes and appearance. The D25 NC uses an automated turntable set-up to take measurements of the entire sample automatically by turning the dish for an adjustable amount of time.

A sample dish would be provided so the beans would be poured into the dish and placed on the turntable. Enough of the sample should be provided that it should cover the entire dish but if there is the odd gap it does not matter as height tolerances can be set to ignore the base of the dish. The turntable will spin for a set amount of time, dependent on individual preference and data will appear in a variety of indices, relevant to the manufacturer and the purpose of colour measurement.

Once the first measurement has been taken, another measurement could be taken to give a broader representation of the beans in the tray. The dish of the sample can either be turned or shaken to move the sample around slightly or, if enough of the product is available for analysis, discarded and replaced with another lot of sample. Taking multiple measurements in this way will allow for a broader view of the quality of the product and data from all measurements can be calculated into an average, making comparing data easier. As this instrument is easy to clean, multiple sample types can be measured with little to no intrusion on the regular processes.

The brief method detailed above is a guide to demonstrate that appearance analysis, whilst providing extremely accurate and detailed results, need not be complicated to incorporate in any company’s quality control processes.

Content Written by Rachael Stothard

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How to measure the colour of different beans

HunterLab D25 NC Spectrophotometer

Evolutionary & Revolutionary

Combining its unique automated motion with the ability to measure and average up to 5 readings per second, the D25 NC is unsurpassed in its ability to accurately measure large, irregular shaped samples of any type. From beans and chips, to plastic pellets, the D25 NC is the ultimate choice for colour measurement.

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