If you have sharp eyes and read your User’s Manual, you may have noticed that two different tomato score formula sets are now available with purchase of the D25 DP-9000 tomato score option. The first is the “older,” or legacy, scores, which should be used by operators who have employed these scores in the past or those who wish to compare samples read with historical data or data from other users using these legacy scores. These scores are defined as follows:
1. Tomato Juice = TJS = 29.600 + 0.88354a - 1.8553b
2. Tomato Paste and Tomato Puree = TPS = -46.383 + 1.0211a + 10.607b - 0.42198b2
3. Tomato Sauce = TSS = -154.39 + 1.1142a + 22.596b - 0.86736b2
4. Tomato Catsup = TCS = -74.937 + 7.5172a - 0.1278a2 - 0.8051b
The history of these legacy scores is as follows:
In the late 1970s, the United States Department of Agriculture (USDA) conducted a series of tests to develop conversion equations relating tristimulus colorimeter readings to scores defining the visual acceptability of certain tomato products. In a memorandum written by Teri Wolcott, et. al. at the University of California, Davis, these conversion equations were defined for colorimeters and spectrophotometers of several manufacturers, including HunterLab’s D25A. These are the legacy equations given above.
In 2001, HunterLab undertook qualification of the LabScan XE and ColorFlex Tomato on tomato products. The D25A DP-9000 was requalified at the same time to account for small changes in the optical design that occurred over the years. This work was completed in July of 2003. The “new,” or 2003 tomato scores were the result. These scores should be used by operators who are beginning to use tomato scores or the D25A DP-9000 for the first time.
The formulas are as follows:
1. Tomato Juice Score = TJS = 25.715 + 0.956a - 1.748b
2. Tomato Paste/Puree Score = TPS = -58.296 + 1.093a + 12.120b - 0.480b2
3. Tomato Sauce Score = TSS = -180.263 + 1.145a + 26.413b - 1.012b2
4. Tomato Catsup Score = TCS = -99.999 + 9.532a - 0.166a2 - 0.936b using C/2°.
Like the legacy scores, these scores have been deemed compliant with USDA expectations. USDA’s letter of July 10, 2003 is shown below.
The difference between the formula sets is not large, but may be significant, depending on your tolerances. Therefore, HunterLab recommends choosing one set for consistent use. The table below compares the two sets for some typical tomato product samples.
(See attached pdf file for the complete article with images and formulas)