Chromatography

EXPERIMENT 8 COLOUR MEASUREMENT OF FOOD PRODUCTS USING A CHROMA METER OBJECTIVE: 1. To measure the colour of food products 2. To studies the application of chroma meter INTRODUCTION Colour models are used to classify colour and to qualify them according to such attributes as hue, saturation, chroma, lightness, or brightness. Chromameter are used to detect colour and measure correlated colour temperature and the difference from the blackbody. There are some methods that are used in colour measurements that are used by chromameter for example; tristimulus value (X, Y, Z) can specify colour such as lightness (light or dark), hue (red, orange, yellow, and green, blue, purple) and saturation (pink-red; pastel-fluorescent; baby blue deep blue). In addition, Munsell system that was created by Munsell modelled his system as an orb around whose equator runs a band of colours. The axis of the orb is a scale of neutral grey values with white as the North Pole and black as the South Pole. Extending horizontally from the axis at each grey value is a gradation of colour progressing from neutral grey to full saturation. With these three defining aspects, any of thousands of colours could be fully described. Munsell named these aspects, or qualities as Hue, Value, and Chroma. In interpretation of colour, the value that was given from the chromameter was used in order to interpret the colour of the food. There are some colour spaces that are used depending on the type of the foods. A colour space is a means of uniquely specifying a colour. The example of colour space include, L* a* b*, Yxy, L* C* h*and XYZ. Each of the space indicates the colour and chromaticity. In this experiment, the colour of

different types of apple and turmeric powder was determined by using chroma meter.

MATERIALS 1. Turmeric powder (BABAS, ADABI) 2. Apples (Apple A , Apple B) 3. Chroma meter (CR400, Konica Minolta, Japan) METHODS 1. The power of the measuring head of the chroma meter was switched on 2. The power of the PC linked to the chroma meter was switched on 3. The SpectraMagic NX icon was doubled clicked on the desktop screen 4. The connect icon on the software task bar was clicked to connect the measuring head to the PC 5. The File/New/Standard was choosed from the menu and OK was 

clicked to start Calibration 1. Data/Observer & Illuminant was choosed from the menu 2. 2 degree was selected in the observer dialogue box, and OK was clicked twice 3. Instrument/calibration was selected from the menu 4. The calibration white tile plate was placed on the top of the measuring head and “white calibration” was pressed. The calibration was completed after the sound of three beeps appeared 5. The menu Instrument/Set calibration data was selected to check on the value of calibration with the white tile (D65: Y=93.9, X=0.3155,



y=0.3318) Measurement of Sample 1. The sample was placed on top of the measuring head 2. The icon “measure sample” was clicked on the menu 3. The name (sample ID) was key in and OK was pressed 4. ABS/DIFF was pressed to view the absolute/differential measurement data condition (Yxy / L*a*b* / L* C* h* / XYZ)

DISCUSSION Through the experiment, the colour measurement of different brand of food products which are red apple and turmeric powder was determined by using a chroma meter. Colour space that was used are L*a*b* that was created by Munsell system whereby Munsell modelled his system as an orb around whose equator runs a band of colours. L* a* b* is one of the uniform colour spaces defined by CIE in 1976 in order to reduce one of the major problems of the original Yxy space. On the other hand, colour is an important quality attribute in the food as it can affect and influences consumer’s choice and preferences. In this experiments, the colour space L* a* b* was selected and the colour of the samples was measured and the reading from the display panel was directly read. The colour interpretation was also interpreted by referring to reference colour book by Konica Minolta. L* indicates lightness and a* and b* are the chromaticity coordinates. Meanwhile, the value of positive and negative of the measurement also play important role in colour interpretation. In addition, the negative value for a* show the green direction. Meanwhile, b* show positive which are in yellow direction. Based on the results from different brand of Apple (Apple A and Apple B) and turmeric powder (BABAS and ADABI), the result for apples shows that’s the lightness of Apple B was more lighter (L*=41.81) than apple B (L*=31.12). Meanwhile the value of a* (27.44) space for Apple A shows that the colour are more to red direction and the value of b* (10.64) indicate to yellow direction. As the reading shows the positive value of colour interpretation hence the intercept reading from the colour space Munsell system was measured. Thus, the interpretation of the Apple A shows that combination of orange and red is present.

In contrast, the result for apple B shows that’s the value of a* (37.24) is more to dark red in colour while the value of b*(20.39) indicate to yellow direction interpretation hence the intercept reading from the Munsell system’s colour spaces was measured. Thus, the interpretation of the Apple B shows that combination of orange and lighter red is present. Hence, the colour of Apple B was lighter in red colour compared to Apple A. On the other hand, for turmeric powder colour evaluation, different brand of turmeric powder was used which are BABAS and ADABI. For BABAS turmeric powder colour interpretation, the lightness of BABAS (L*=64.54) shows that it was slightly darker compared to ADABI (L*=67.33) turmeric powder. The different in lightness might results from different type of processing of the powder such as the time taken and temperature that has been conducted by different brand during the processing of turmeric powder. Besides, the other colour space for BABAS turmeric powder is (a*=18.77) and (b*=53.13). From the intercept reading that was measured from the L*a*b* colour space in Munsell

system, the

interpretation colour of the BABAS turmeric powder shows that the combination of yellow and orange colour was present. Meanwhile, ADABI turmeric powder colour space of a* and b* was 14.98 and 55.59 respectively. The intercept reading from the Munsell system colour space shows that the colour was more to light yellow and orange. Hence, ADABI turmeric powder was lighter in yellow colour compared to BABAS turmeric powder colour. During the experiment, they are some sources of error that occur which may affect the accuracy of the result. For example, the colour measurement on the apple surface was not even as there is some curve on the surface of the apple. To minimize these errors various precautions should be taken such as, make sure an even surface of measurement was taken during measuring and three consecutive of measuring need to be carried out to eliminate the errors of the handlers.

CONCLUSION In conclusion, the colour space interpretation of Apple A is L*=31.12,

a*=27.44

and

b*=10.64.

Meanwhile,

the

colour

space

interpretation for Apple B is L*=41.81, a*=37.24 and b*=20.39. Hence, the colour of Apple B was lighter in red colour compared to Apple A. In contrast, the colour space interpretation of BABAS turmeric powder is L*=64.54, a*=18.77 and b*=53.13. Meanwhile, the colour space interpretation for ADABI is L*=67.33, a*=14.98 and b*=55.59. Hence, ADABI turmeric powder was lighter in yellow colour compared to BABAS turmeric powder colour.

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from

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and from

http://eprints.ru.ac.za/407/1/HaighJM_Analysis.pdf Pankaj B. Pathare. (2012), Colour Measurement and Analysis in Fresh and Processed Foods: A Review" Food and Bioprocess Technology, Retrieved http://works.bepress.com/pankaj_pathare/3/

from