14 August 2015
Coffee is one of the most consumed beverages worldwide with over 400 billion cups being drunk every year. The perception of coffee beans being used in beverages compared to the use of instant coffee granules is so prestigious that consumers pride themselves on using only the finest coffee beans they can get. If you were to imagine a market vendor selling coffee beans of different flavours and types, the appearance is the first attribute the customer will be evaluating; if any of the beans appear too light or dark or of a different hue, they will not even be considered, regardless of the aroma or taste.
Points to think of:
Why are we analysing appearance?
When completing any analysis of colour and appearance it is important to know from the start why measurements are being taken. Are customers claiming a difference in colour and therefore consistence? Are samples coffee beans being compared to those from different suppliers to find the beans of consistently good quality? Is the data being used to ensure top quality products over time? Is the data being used for research and development processes? Whatever the reason for colour measurement, the methodology should suit the needs of the customer and work well within the production processes.
How many measurements?
The amount of measurements taken is dependent on the time available for testing, how much sample is available for testing, how accurate the data needs to be and what instrument is being used for testing. Generally speaking, the more measurements taken, the better the data received represents the batch of product as a whole. For samples of irregular appearance, data taken over a number of samples combined to form an average is a more precise method for data analysis.
How much sample?
Similarly to how many measurements are needed, the more sample tested the better. An ideal method is to calculate an average using the data collected. A sample of the product should be measured then, depending on how much sample is available, the sample should be replaced with more from the same batch or turned to provide a different surface to measure. The main aim of this is to give a broader view of the batch being produced; this can be repeated as many times as required.
When to measure
Most production processes, whilst very similar across the industry, are naturally modified to individual manufacturers in keeping with specific recipes or methods of production. For the majority, there are a few stages in which colour can be measured, depending on the amount of time available for evaluating quality and also the instrument being used and its capabilities. The best points to take measurements would be when the appearance of the bean best represents the final product or when the appearance of the bean will be changed by processes such as roasting. Analysis after these process can not only provide data relating to bean appearance but also monitors the effectiveness of the different processes.
At the very least, a sample should be measured before the product is packaged ready for shipping. Taking a measurement at this stage acts as a final check to make sure no substandard product leaves the processing plant.
What data should be analysed
To have as much relevant data as possible, measuring with either Hunter L, a, b or CIE L*, a*, b* can give a detailed idea as to the colour of the sample. For more detail, the HCCI (Hunterlab Coffee Colour Index) can be used or the sample compared to SCAA (Specialty Coffee Association of America) standards. When using software, many more indices can be used to gather as much in depth data as is required.
A Tool for the Job
The main options available for coffee analysis would be to use either a Colorimeter or Colorimetric Spectrophotometer, but which one? A tristimulus colorimeter can measure colour and the technology is built with the older optical filter design. A Colorimetric Spectrophotometer, on the other hand, carries out colour measurement avoiding the variation of the optical filters and provides a far more detailed analysis of colour by, in this case, obtaining accurate reflectance colour data over the visible spectrum. Its reliability of measurements for longer periods of time make it an ideal tool when measuring a mass produced product for public consumption.
A Spectrophotometer should be used that is capable of measuring and acquiring data of irregular solid samples. The ability to measure samples of different surfaces means that the quality control process can be a quick and productive one.
A couple of examples
The D25NC Spectrophotometer is designed to excel at irregular shaped and coloured samples. This space saving instrument allows non-contact measurements of a larger sample size that will create better average data readings and therefore more accurate results. This instrument can accommodate the beans throughout the manufacturing process, giving accurate reflected colour data for examination at any stage.
Versatility is an important factor within any manufacturing or production process as it can allow for any eventuality and compliment the quality control processes without hindering them. Whatever instrument chosen it should be ensured that it can give accurate data that can resolve any colour issue and help keep quality as good and consistent as expected.