Farm Focus: All Things Brix

Every once in a while you will hear us throw around the word Brix in reference to our fruit's sweetness and we thought now, in the heart of stone fruit season, would be a great time to explain what a Brix test is and why we do it!

The Brix test is a measurement for testing fruit sweetness. More accurately it is a measurement of the soluble solids content of a liquid. In fruit juice most of those soluble solids are sugar so this means the higher the Degree Brix (usually just called Brix), the higher the sugar content, which means a sweeter fruit! This measurement is used throughout agriculture and is very common in winemaking because sugar levels are directly related to the fermentation process.

To Brix test stone fruit we cut off the bottom of the fruit and squeeze some juice into a refractometer and put it up to the sun. Refractometers work like a prism- separating different wavelengths of light. It reacts differently depending on the amount of sugar present in the sample and reads out on the scale.

Most store-bought fruit, especially fruit that is transported long distances, has to be picked while the fruit is still hard so it can survive transportation. This means that it has less of a time to soak up sugars from the tree. Here at Frog Hollow Farm we pride ourselves on giving fruit a little extra time on the tree for full tree-ripened flavor. The Brix for typical store-bought peach, for instance, will come in around 10 to 11 while we aim to pick our peaches around 12 to 14. Summer fire nectarines, coming in this week’s box, are the second sweetest nectarine we’ve harvested so far this summer coming in at 19.68. Flavor King Pluots are nearing cherry level sweetness with their Brix averaging 21.97! Most people's palates prefer a nice balance of sweet and acid so some varieties might score relatively low Brix but, because of their acidity and flavor still taste delicious.

While it is wonderful to quantify the sweetness of our fruit, Brix testing is, more importantly, a tool for monitoring crop ripeness. Each week Rachel and Danielle, our summer intern from UC Davis, test the fruit ready for harvest. We track each variety in the orchard on a big spreadsheet to track harvest times and yields over the years. By using the Brix test to check in on these crops we are able to monitor ripening rates. It is an especially useful tool when, like this year, we are harvesting new varieties of fruit we’ve never grown before. We will do Brix tests on these varieties more frequently on as a way to get to know the rate of ripening and when they are ready to harvest.

One of the best parts of the afternoon at the farm office is when Rachel or Danielle come through when a big platter of freshly Brix tested fruit. The bottoms are cut off so you can see the wonderful color of peaches, nectarines, plums, and pluots. While they still might be harvested underripe it is amazing how sweet they are using the original Brix test… tastebuds!