Why Dry Matter Matters In Apples
Apples have long been known for their bright, bold, and beautiful appearance. Sometimes, though, consumers found these beautiful “typey” apples, such as Red Delicious, lacked in flavor and their preference shifted from looks alone to flavor and crunch. The adage “what’s inside matters most” could not be truer. Research is being conducted to help breeders and growers build the perfect apple by understanding its internal chemistry, specifically the dry matter content.
Why Dry Matter Matters
What exactly is dry matter? The simple answer is everything in the apple minus the water.
“Dry matter is the accumulated sugars, cell wall, proteins, and starch that are present in the apple. All of this is derived from the photosynthetic activity in the leaves and enters the fruit as sugar and is subsequently metabolized into storage (starch), enzymes (protein) and/or cell wall material. As the fruit grows and matures it accumulates dry matter,” says Peter Toivonen, a postharvest physiologist with Agriculture and Agri-Food Canada.
Dry matter gives you an insider’s view of what’s going on within the apple. Some researchers say accurate reads of dry matter content, or DMC, can help you gauge the ripening state of your apples, help you see if there is an issue with your crop, and can help you establish when to harvest your fruit. Understanding the nuances of dry matter can give you a leg up on your competition because there is a direct correlation between consumers’ preference and varieties with high DMC.
“[Dry matter] measures the biological process as it happens on the tree — you can start to see early on if there’s a problem. For growers, they have information they can share with the supply chain,” says Roger Harker, principle scientist with Plant and Food Research in New Zealand. “There are opportunities to use [the information] more so you can understand well before harvest what the fruit is likely to be.”
How You Can Test For Dry Matter
Testing for dry matter content is not a new concept. The standard method has been to cut apples into quarters or thin slices, weigh the quarters and dry them in an oven for approximately 48 hours, or until weight loss is no longer detected. The final weight divided by the original fresh weight is the dry matter reading. This testing for dry matter is referred to as “destructive” methods.
While common, using destructive methods like these to assess dry matter can be time-consuming, and there is a wait to get a reading of the fruit’s maturity. The same is true of the starch pattern index, familiar to many growers, which has traditionally been used to track maturity.
“Apples are now picked on starch degradation. It’s a common index for harvesting. In apples, there is a scale of value that corresponds to starch degradation,” says Stefano Musacchi, associate professor of tree fruit physiology and management with Washington State University.
Both Felix Instruments and T.R. Turoni have handheld meters that use infrared technology to assess fruit in a nondestructive method. Felix Instrument’s F-750 Produce Quality Meter captures the range of Brix, color, acidity, and dry matter. T.R. Turoni’s DA meter measures the chlorophyll content in a fruit immediately below the skin, giving an index of the fruit’s ripening state.
“The DA meter can integrate the information the starch degradation provide to the growers. Something that can be very useful to better define the ripening stage of the fruit,” says Musacchi.
As fruit matures, it loses chlorophyll. The DA Meter “puts a number to this loss of chlorophyll,” says Jon Clements, Extension Educator, University of Massachusetts Amherst.