Color Classification: Utilizing Spectrophotometry for Analysis and Grading of Tomato Products

Spectrophotometry
The eye-catching colors of tomatoes act as clues to their taste and quality.
Image Source: Flickr user rpavich

October is National Tomato Month and to honor the occasion, wellness company Lycored set out to create a record-breaking 1000-pound tomato salad in the middle of Times Square. Featuring 132 types of tomatoes in a rainbow of hues, the salad presented the largest variety of tomatoes ever assembled in a single location. And yet, even this vast array represents only a small proportion of the ever-expanding number of tomato varieties in existence.

The diversity of tomatoes and dedication to creating new varieties speaks to the global, cross-cultural appeal of the fruit. As horticulturalist and tomato-expert Monica Ozores-Hampton says, “People have these romantic ideas about tomatoes. People always have a story about that favorite soup or pizza and they yearn for the tomato. There is not one culture that doesn’t have tomato as a centerpiece of their culture’s cuisine.”1 Given the central role tomatoes play in the dining experiences of people across the world, it is no surprise that spectrophotometric quality control is paramount to producers of both fresh and processed tomatoes.

Spectrophotometry
Grading of processed tomato products relies on spectrophotometric color measurement.
Image Source: Flickr user Steven Depolo

Spectrophotometric Grading of Tomato Products

While raw tomatoes come in a wide variety of colors and flavors, USDA grading of tomato products such as pastes, sauces, ketchups, and juices depends on adherence to specific color standards to indicate quality. Each grade has exact color ranges and where a product falls within that range can have a significant impact on consumer perception and success in the marketplace. Although archaic visual comparison methods are still in use, spectrophotometry has long been utilized to provide more precise grading and the USDA is now encouraging producers to turn to electronic color measurement. HunterLab’s spectrophotometric instruments and conversion formulas are recognized by the USDA as the premiere tools available for color classification of tomato products.

Although a number of multi-purpose HunterLab instruments meet the criteria for tomato evaluation reliability, we also produce a dedicated tomato spectrophotometer: the ColorFlex EZ Tomato. By combining optimal 45º/0º geometry with specialized firmware for the analysis of fresh and processed tomatoes, the ColorFlex EZ Tomato allows for easy determination of tomato color classification. Scales include:

  • Fresh Tomato Index (FTCI)
  • Tomato Paste Score (TPS)
  • Tomato Sauce Score (TSS)
  • Tomato Catsup Score (TCS)
  • Tomato Juice Score (TJS)
  • a/b ratio

HunterLab also offers a tomato tile to ensure accurate, repeatable measurement over time and hitch standardization between instruments, optimizing tomato color analysis and grading throughout production. In addition to measuring processed tomato products, raw tomatoes may also be measured to indicate ripeness, freshness, and overall quality.

spectrophotometry
Lycopene content increases as tomatoes ripen and is primarily concentrated in the skin of the fruit.
Image Source: Unsplash user Deniz Altinda

Spectrophotometry for Lycopene Measurement

The color changes that occur during the ripening of tomatoes are the result of falling chlorophyll levels and increasing carotenoids. The primary carotenoid in tomatoes is lycopene, a chemical renowned for its health benefits and the central component in creating tomatoes’ rich, red hue. Lycopene levels are not static, but vary depending on tomato type and growing conditions and have a direct relationship to the color of the fruit. Spectrophotometric instrumentation provides a highly reliable method of measuring lycopene concentration in both fresh tomatoes and tomato products by quantifying colorimetric data to produce a Lycopene Index number.2 HunterLab’s sophisticated CFEZ Tomato firmware offers the most precise Lycopene Index calculation using Hunter a and b color values gained via a directional 45º/0º geometry instrument.

The Gold Standard

HunterLab has been a pioneer in the field of tomato color measurement for decades. In fact, when the first correlation between visual and instrument-based scoring was developed in the late 1970s, the USDA considered the HunterLab D-25 A the gold standard for evaluating tomato scores.3 Today we have taken tomato color measurement to even higher levels of precision through advanced spectrophotometric instrumentation and custom firmware and software packages that allow you quantify chromatic information with ease. Contact us for more information about our innovative product range and dedicated customer support services.

  1. “National Tomato Month: Largest Tomato Salad Sets Guinness World Record In Times Square,” October 13, 2015, http://www.medicaldaily.com/national-tomato-month-largest-tomato-salad-sets-guinness-world-record-times-square-357086
  2. “Lycopene Concentration of Tomato Fruit can be Estimated from Chromaticity Values,” 1992, http://hortsci.ashspublications.org/content/27/5/465.full.pdf
  3. “Color Quality in Tomato Products,” 2008, http://www.fruitandvegetable.ucdavis.edu/files/217108.pdf

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