Fruit and Vegetable Program

Specialty Crops Inspection (SCI) Division

SUBJECT: Tomato Products Spectrophotometer Studies

In March 2008 Processed Products Branch (PPB) in cooperation with the University of 

California, Davis (UCD) completed a study of the Minolta Konica CR410 spectrophotometer

for use in the evaluation of "color" in tomato products. The study was initiated to consider 

additional instruments for approval at the request of instrument suppliers. PPB currently 

maintains a list of approved instruments including the Hunter Lab D25-D2 series; Agtron M400, 

M500, and E5M Colorimeters; and BYK Gardner models XL20, XL23, XL-805, and Colorgard 

2000/05.

The study compared the Hunter Lab Scan XE from Hunter Lab and the UCD reference 

spectrophotometer (Hunter Lab Scan 5100) to the Minolta Konica model number CR410.

Samples of commercially prepared tomato products were purchased from grocery stores in the 

Davis, Sacramento, Vacaville, CA and Reston, VA areas. The illuminant used for the color study 

was CIE illuminant C. The standard observer was 1931, 2 degrees Standard Observer.

As a result of the study and determinations made by PPB, the following spectrophotometers and 

the equations associated with each instrument are approved for the calculation of the color score 

for products covered by the U.S. Standards for Grades of Canned Tomato Sauce, Tomato Juice, 

Tomato Juice from Concentrate, Tomato Paste, Tomato Puree, Concentrated Tomato Juice, and 

Tomato Catsup.
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Minolta Konica model number CR410

Tomato Sauce Score: TSS = -51.231 + 1.463 a + 13.986 b - 1.021 b2

Tomato Catsup Score: TCS = -50.28 + 9.956 a - 0.263 a2 - 2.76 b

Tomato Juice Score: TJS = 25.51 + 1.406 a - 2.97 b

Tomato Paste and Puree Score: TPS = -1.345 + 1.253 a + 7.733 b - 0.574 b2

 where a and b are from Hunter L, a, b values.

BYK Gardner Color View

Tomato Sauce Score: TSS = -227.607 + 1.154 a + 33.615 b -1.278 b2

Tomato Catsup Score: TCS = -59.387 + 5.635 a - 0.0990 a2 + 0.414 b

Tomato Juice Score: TJS = 95.652 + 0.956 a - 11.840 b + 0.379 b2

Tomato Paste and Puree Score:

TPS = -2.63270 + 13.822 log b - 7.422 log L + 0.0234 a - 1.002 b + 0.295 L

 where L, a, and b are readings reported by the instrument.

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HunterLab ColorFlex 4500L

Tomato Sauce Score: TSS = -153.100 + 1.187 a + 22.332 b - 0.864 b2

Tomato Catsup Score: TCS = -80.888 + 8.355 a - 0.144 a2 - 1.194 b

Tomato Juice Score: TJS = 25.963 + 0.989 a - 1.787 b

Tomato Paste and Puree Score: TPS = -81.582 + 1.069 a + 15.390 b - 0.591 b2

 where a and b are readings reported by the instrument.

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Hunter D25A-9000

Tomato Sauce Score: TSS = -180.263 + 1.145 a + 26.413 b - 1.012 b2

Tomato Catsup Score: TCS = -99.999 + 9.532 a - 0.166 a2 - 0.936 b

Tomato Juice Score: TJS = 25.715 + 0.956 a - 1.748 b

Tomato Paste and Puree Score: TPS = -58.296 + 1.093 a + 12.120 b - 0.480 b2

 where a and b are readings reported by the instrument.
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Hunter Lab Scan XE

Tomato Sauce Score: TSS = -149.176 + 1.139 a + 21.608 b - 0.826 b2

Tomato Catsup Score: TCS = -81.964 + 8.321 a - 0.142 a2 - 1.129 b

Tomato Juice Score: TJS = 25.114 + 0.939 a - 1.638 b

Tomato Paste and Puree Score: TPS = -40.926 + 1.061 a + 9.473 b - 0.376 b2

 where a and b are readings reported by the instrument.

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The following equations are used for the calculation of color score for the previously approved 

colorimeters for tomato products. 1/

Hunter D25-D2 Colorimeter

Tomato Sauce Score: TSS = -154.39 + 1.1142 a + 22.596 b - 0.86736 b2

Tomato Catsup Score: TCS = -74.937 + 7.5172 a - 0.1278 a2 - 0.8051 b

Tomato Juice Score: TJS = 29.600 + 0.8835 a - 1.8553 b

Tomato Paste and Puree Score: TPS = -46.383 + 1.0211 a + 10.607 b - 0.42198 b2

 where a and b are readings reported by the instrument.

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Agtron M400 and M500 Colormeters

Tomato Sauce Score (tentative): TSS = -25.002 + 1.5234 R - 0.0092174 R2 - 0.25817 G 

Tomato Catsup Score (tentative): TCS = -5.3411 + 1.0309 R - 0.00745 R2 - 0.15663G 

Tomato Juice Score: TJS = 28.629 + 0.1428 R - 0.24197 G + 0.14176 B

Tomato Paste and Puree Score: TPS = 20.850 + 0.828 R - 0.004335 R2 - 0.283 G + 0.312 B

R = Red, G = Green, B = Blue

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1/

These equations are based on Hunter a and b values referenced in the initial study by USDA at 

UC Davis entitled, “Color Scoring Tomato Color Measure”, by George Marsh, James Buhlert, 

Sherman Leonard, Teri Wolcott and Julie Heil, Dept. of Food Science and Technology, 

University of California, Davis, July 15, 1980. 
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Agtron E5M Colorimeters

Tomato Sauce Score (tentative): TSS = 38.936 - 0.45231(E5M Reading)

Tomato Catsup Score: TCS = No equation is available for an accurate color score for catsup.

Tomato Juice Score: TJS = 40.898 - 0.35759 (E5M reading)

Tomato Paste and Puree Score: TPS = 54.250 - 0.005265 (E5M Reading)

2

For Tomato Paste and Puree having a brown or burnt visual appearance the Agtron E5M meter 

reading yields accurate “substandard” scores.

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BYK Gardner XL20, XL23, XL-805, and Colorgard 2000/05 Colorimeters

Tomato Sauce Score (tentative): TSS = -193.20 + 1.0211 aL + 27.649 bL - 1.0175 bL

2

Tomato Catsup Score: TCS = -40.511 + 4.7767 aL - 0.07791 aL

2 - 0.56986 bL

Tomato Juice Score: TJS = 34.094 + 0.71464 aL - 1.7883 bL

Tomato Paste and Puree Score: TPS = -46.383 + 1.0211 aL+ 10.607 bL - 0.42198 bL

2

 where aL and bL are readings reported by the instrument.

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