DigiPix > CASE STUDY: CCFRA
The ORGANISATION
CCFRA Group (Campden and Chorleywood Food Research Association) is the UK's largest independent membership-based organisation carrying out research and development for the food and drinks industry worldwide. It is committed to providing industry with the research, technical and advisory services needed to ensure product safety and quality, process efficiency and product and process innovation.
Through a continuous programme of investment CCFRA ensures leading edge processing and analytical facilities for research and contract work. In October 2003 the Group initially purchased the DigiEye System to use in an industry funded project to establish objective ways of measuring the appearance of food including its colour and now has DigiEye systems in their laboratories in the UK and Hungary used for research and contract work for applications which include studies of the effects of food processing variations. It is also being used to produce reliable, meaningful images for companies on their extensive client base.
CURRENT METHODS OF COLOUR MEASUREMENT
People buy food with, amongst other senses, their eyes. Therefore the colour and aesthetic appearance of food products is a critical element for the consumers and therefore an important quality attribute of the product.
However traditional instrumental measurement of food products is restrictive; obtained using a colorimeter or spectrophotometer, measuring only a limited area of the product with subsequent data being an average colour of the selected area.
Photographic images are also currently used by the food industry for the appearance of product to provide specification standards for quality control comparisons but the reproduction of the images is inconsistent and the variables of image, printing and viewing consistency prevent such images being relied upon for true reliable control of the quality of food product.
THE APPLICATIONS
The DigiEye system includes a calibrated digital camera; printer and monitor and also critically a lighting environment for image capture which ensures consistent colour and lighting. The immediate advantage over traditional methods is the ability to capture an accurate colour, which will match the actual appearance of the product.
As the DigiEye system has applications and capabilities well beyond those achievable with traditional measurement techniques CCFRA uses the system in two distinct areas and end-uses;
- To provide good consistent calibrated images and
- As a reliable colour measurement tool
CCFRA are able to measure spatial variations of colour within a product or from product to product across very diverse, and arguably limitless, types of food product. The examples below illustrate how colour distribution can be measured through a melon from centre to edge to assess and quantify the colour variation and also the differing shades of tomatoes in a selected punnet.
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One of the significant advantages of the DigiEye system allows, due to the consistency of the images taken, direct comparisons to be made between images taken of product in different locations worldwide and at different times.
This benefit, together with the ability to subsequently send images electronically, with the associated colour measurement data, ensures reliable visual comparisons.
The greater versatility offered by DigiEye over the measurement obtainable from a standard colorimeter makes the system an invaluable application for companies in the food sector to achieve the desired objective - ensuring the consumer is able to buy consistent and reliable product. This versatility allows specific regions of a diverse selection of food and food components to be imaged and reliable, quantifiable colour measurements to be available for analysis.
The image above of leeks illustrates the use of DigiEye to measure the colour variation along the length of the leeks; this information was used to create a plot of distribution of colour against distance from the root end. This can be used to determine the average length of the white part of the leek.
THE TECHNICAL BIT
The DigiEye system gives accurate and reproducible colour reproduction.
- The devices - camera and monitor are calibrated against the CIELAB system to establish the relationship between RGB colour values and CIELAB values. The images can then be converted to CIELAB colour space, enabling consistent and traceable results to be obtained for the images. Images taken using different DigiEye systems or at different times can then be compared.
- The product samples are captured in standardised conditions; this is achieved by placing the samples in a cabinet with a neutral grey interior which is illuminated by a light produced by VeriVide, the world leaders in the design, development and manufacture of highly specialist viewing assessment equipment for all industries.
- The light used in this DigiEye system closely matches the CIE D65 lighting; the standard generally used for colour measurement.
- DigiEye can be used with different illumination geometries. The Diffuse illumination setting is suitable for many applications, including the imaging of samples with a glossy surface, as it then avoids bright specular reflections in the image. Alternatively, directional illumination can be set at any of several fixed angles to enable the surface texture of the subject to be revealed more clearly.
APPLICATION 1. – COLOUR MEASUREMENT OF A SPECIFIC AREA OF A PRODUCT
The DigiEye system provides objective, consistent and reliable measurements of a wide array of the characteristics of a seemingly unlimited range of food types, products and food constituents.
At CCFRA it has been used to measure, for example, the shape, size and structure of food including the thickness of bread crust and the distribution of cherries within fruitcake.
The use of the DigiEye system enhances the existing image analysis systems and measurement tools already used at CCFRA adding the capability to measure colour from images - thereby increasing tremendously the scope and versatility of services offered. In addition to the average measurement of colour of a product achievable with existing facilities, the distribution of the differing colours within food products can also be measured and recorded for further analysis.
Examples of this type of application include measurement of bread assessing the visual colour effects of differing baking times upon the crust in terms of, for example depth, saturation and distribution of the colour over the surface. The aim being to offer the facility to produce definitive colour reference scales for various foods for use by CCFRA members
DigiEye offers measurement of colour and aesthetic appearance that is quantifiable, has traceability and objective consistent data.
The image of baked beans shows examples of three different brands, the production methods result in differences in sauce colour. DigiEye was able to image the samples, measure the sauce colour and the beans independently and in-situ and analyse the colour variation between the brands.
This would have been difficult to assess with a standard colorimeter due to the combination of beans and sauce and the glossy appearance of the product. The system, by enabling quantifiable and objective Quality Control is a tool which can assist in delivering the visual expectations of customers.
APPLICATION 2. – VISUAL QC
As a result of the accurate and reproducible colour reproduction achieved by DigiEye, images taken by CCFRA can be used for visual assessment and comparison against an established standard, either via the calibrated monitor or by colour accurate printing.
CONSISTENT LIGHT SOURCE
The factors affecting the visual appearance of a product are not only a result of the reflectance of the sample but also the light source under which it is viewed or intended to be viewed. It is therefore essential, before the commencement of any colour measurement work, to establish the required illuminant in which the product is to be viewed.
The DigiEye has a fixed light source of D65 – artificial daylight (this is also a common light source within the food sector) but is able, through the software, to stimulate and give results in other standard light sources. The colour measurement and images produced at CCFRA are intended for viewing under D65 illuminant.
The consistency of the viewing lighting is critical due to potential issues with metamerism, this is the experience whereby objects appear to have different colour when viewed in different lightings. (Examples of metamerism often include clothing and furnishings which, once back at home, “look nothing like the colour they did in the shops”.)
For reliable viewing during product assessment it is therefore important to standardise the light source to ensure compatibility between the visual standard and the product viewed from a production line on the factory floor. VeriVide produce a range of viewing cabinets, with a range of differing illuminants ideal for this end-use that are essential for visual assessment of the colour and appearance characteristics of food samples.
The image of bread rolls below illustrates diverse variation in the crust colour of a selection of bread rolls. These rolls can be imaged with DigiEye individually or as a group to produce appearance standards for crust colour.
IMAGE OF BREAD ROLLS
These standards can be issued to manufacturing units as photographic standards, eliminating the inconsistencies in colour reproduction that commonly exist in the wide use of photographic product images for use of the quality control of food products. The use of DigiEye, in conjunction with the appropriate VeriVide viewing cabinet, for the first time offers a reliable and accurate method for visual QC of food product.
APPLICATION 3 – COLOUR CLUSTERING
The Colour Clustering technique within the DigiEye system automatically groups pixels of the same colour together and then calculates the percentage of the total pixels within the image. By measuring the proportion of different colours within an image, this feature has uses within a range of industries, including the food sector.
This function can be used to calculate the proportions of different coloured components in a food and is able to calculate the percentage amount as a whole or in relation to the distribution of the various constituents of a food sample that are present and visible within that food sample.
The colour clustering function can enable differently coloured regionsto be identified automatically. CCFRA have developed additional software to analyse images produced by the DigiEye system for particular applications in their laboratories. They have used a similar clustering approach to identify differently coloured regions of images, enabling further measurements then to be made for each of the regions.
The screenshot below of the two slices of cherry cake shows, by the use of their own additional software, the following data was extracted by CCFRA, after the cake was separated from the background.
- The Colour of the crumbs. Shaded blue in the two images on the right. The cherries (in red) and crust (shown in white) was excluded. To measure the crumb colour using traditional method who have required a measurement of a section of cake which was ‘cherry-less’, making it more difficult to achieve colour measurement data that was representative of the cake slice as a whole. DigiEye can separate and measure differing coloured elements of product such as the crumb colour of a cake.
With the use of their own additional software, CCFRA were able to further analyse samples to provide additional data for both the cherries and the crust.
- The Distribution, Colour, Size and Number of cherries. This enables measurement of the effects upon the height distribution of the cherries in relation to of the viscosity of the cake measure against various cooking procedures and times.
- Crust Thickness. Each pixel, from the edge inwards, was measured to establish the exact measurement of the crust.
SUMMARY
- DigiEye has proved to be a very versatile system for research applications, allowing images to be taken and data interpreted using the software within the system or by other software to make particular measurements or analysis.
- It has allowed CCFRA to document the appearance of samples received from clients for some contracts. This has included documentation of products sent for categorisation by HM Revenue and Customs. These provide useful records for future reference. High quality prints of the images taken with the DigiEye have also been taken to meetings with other customs authorities to assist in ensuring a consistent approach to classification decisions within the EU.
- There are many benefits to food companies and it is inevitable that the use of this system will increase as the food industry becomes increasingly aware of the capabilities of the system through organisations such as CCFRA. DigiEye are collaborating with CCFRA to identify further opportunities for the system in the food industry, and to develop the capabilities of the system to address any new requirements identified.
- It has enabled a system for documenting product trials at CCFRA to be developed and has been used in work for the sea fish industry to assess a new High Pressure Processing method used to help remove shellfish from the shell efficiently while retaining the fish in a raw state. Further details can be seen on the CCFRA Newsletter Aug 2007
- It will certainly be used for more areas of research as its availability becomes more widely known within CCFRA, being applied to more and more ‘funded from industry’ projects.
"The work described here was conducted by CCFRA and we are grateful to Dr. Martin Whitworth for providing the information from the CCFRA studies. The images are CCFRA copyright and reproduced with permission."
Anyone who might wish to find out more about the work at CCFRA please click on the link below.www.campden.co.uk