DA Meter
BC Tree Fruits Grower Services Manager Hank Markgraf demonstrates the DA meter.
Apple quality going into storage is the biggest factor that will determine the quality coming out of storage, BC Tree Fruits (BCTF) Post Quality Development Manager Bill Wolk told the BCTF Hort symposium this spring.
“The CA (controlled atmosphere) operators are good,” Wolk says. “But growers have a significant amount of control over fruit quality.”
A one-day delay in harvest can lead to a difference of weeks in storage life Wolk says. “ A difference of day or two may not be apparent at harvest, but I promise you those are very different fruit coming out of storage.”
AAC Summerland Research Scientist Dr. Peter Toivonen is working with an Italian invention, the DA meter, to help growers better determine optimum harvest times for apples.
Toivonen says the DA meter tells the physiological age of the fruit. Harvest the fruit too early and it will come out of storage hard as a bullet. Harvest it too late and it will be mushy.
“That’s what the packing house wants to know,” says Toivonen. “Are these apples going to hold up? They don’t want to find out in February that the apples are starting to break down.”
LED lights from the meter go into the apple and a sensor measures how much light reflects back out – “the DA” or Delta Absorbance, which reveals the level of chlorophyll that is in the apple peel.
“Chlorophyll concentration is an indicator of how ripe the apple is inside,” said Toivonen. “It doesn’t matter what color the apple is, the DA meter only measures the chlorophyll.”
Toivonen works with Ambrosia, an apple that demands a quick and accurate measure of ripeness. Ambrosia has an average picking window of 10 days, but some years that can be as short as five days. “You have to be fast on your feet and the DA meter allows you to make decisions faster and plan for multiple picks,” said Toivonen.
The instrument is portable, easy to use, reliable, and according to Toivonen’s data over the last six years, an excellent predictor of how well an apple performs during long-term storage.
“It is important to have Ambrosia’s superlative qualities preserved,” says Toivonen. “That’s why people are buying those apples, they are not commodity apples they are premium apples.”