By Heide Dolan, Colorado Master Gardener

Fresh, homegrown tomato season is upon us, and the serene sighs of summer harvest lie just around the corner. Searching for that sweet, yet perfectly balanced, tastiest tomato to grow is a perpetual quest for tomato growers. Did you know there is a scientific way to measure a tomato’s sweetness? Did you also know that curious home gardeners can obtain this device without breaking the bank?

While scientists have used refractometers for years to measure sugars in things like wine, these same devices can also be used to measure tomatoes’ Brix. Brix is a word for sugar content in simplified scientific terms. It doesn’t tell the whole story about tomato taste, but Brix content is certainly a piece of the puzzle. Overall, Brix levels in fruit are dependent and vary, based on plants’ specific genetics, nutrient-dense soil quality, the weather, and also the time of the season when you test. Higher Brix levels happen at peak season and Brix tapers down, sometimes rapidly, as summer ends.

The process of measuring Brix is simple. Calibrate your refractometer according to manufacturer’s specifications. Select ripe fruit to test at peak season when conditions are best. Cut the fruit and squeeze a drop of juice into the open meter window. Boom! A number will display. With tomatoes, that number runs anywhere from 3, for a very tart tomato, all the way to 12 for a very sweet one.

Refractometers are quite compact and can be digital or traditional handheld devices that produce results by looking through a tube to a shaded graph where you can read the levels. Digital models are the simplest and easiest to use when you have gooey hands. Many models of different sophistication and sensitivity levels are available at almost any price point.

Home gardeners who are curious may want to know that size counts here. Cherry tomatoes are the smallest, sweetest and have the highest Brix levels. That Supersweet 100 cherry tomato plant you are eyeing at the nursery is, in fact, sweeter than others. Typical cherry tomatoes run Brix levels of 7 to 12. Roma type tomatoes, such as San Marzano, are generally referred to as pastes. They are fleshy, but not overly sweet with a nice balance of acidity. We all can appreciate that this balance is necessary for a deep tomato sauce. You wouldn’t want a Brix of 10 in a Roma for just that reason. Brix levels of 3.5 to 4.5 are a pretty good benchmark for paste tomatoes. Larger tomatoes also typically have lower Brix contents. Beefsteaks and Oxheart tomatoes can vary greatly in sugar levels. Some popular tomatoes like Cherokee Purple or Kellogg’s Breakfast usually run between 5.5 to 8 Brix.

At this time of year, as we crave a sweet, slobbery, sun-warmed tomato straight off the vine, think about using a new garden gadget – the refractometer. It’s a fun process to measure and record the sweetness of America’s favorite fruit – the homegrown tomato. Are you ready?