Summary:
BACKGROUND: Minolta and machine vision are two different instrumental techniques used for measuring the color of muscle food products. Between these two techniques, machine vision has many advantages, such as its ability to determine L*, a*, b* values for each pixel of a sample's image and to analyze the entire surface of a food regardless of surface uniformity and color variation. The objective of this study was to measure the color of irradiated Atlantic salmon fillets using a hand-held Minolta colorimeter and a machine vision system and to compare their performance.
RESULTS: The L*, a*, b* values of Atlantic salmon fillets subjected to different electron beam doses (0, 1, 1.5, 2 and 3 kGy) were measured using a Minolta CR-200 Chroma Meter and a machine vision system. For both Minolta and machine vision the L* value increased and the a* and b* values decreased with increasing irradiation dose. However, the machine vision system showed significantly higher readings for L*, a*, b* values than the Minolta colorimeter. Because of this difference, colors that were actually measured by the two instruments were illustrated for visual comparison. Minolta readings resulted in a purplish color based on average L*, a*, b* values, while machine vision readings resulted in an orange color, which was expected for Atlantic salmon fillets.
CONCLUSION: The Minolta colorimeter and the machine vision system were very close in reading the standard red plate with known L*, a*, b* values. Hence some caution is recommended in reporting color values measured by Minolta, even when the 'reference' tiles are measured correctly. The reason for this discrepancy in color readings for salmon is not known and needs further investigation. Copyright © 2009 Society of Chemical Industry