2017 Apple Maturity Assessments—Week Four

With the continued cooler temperatures and heavy rainfall in August, fruit size and red color are good. Gala harvest is in full swing; picking began soon after we sampled.
2017 Apple Maturity Assessments—Week Four - News

Updated: October 5, 2017

2017 Apple Maturity Assessments—Week Four

Photo 1: Measuring the starch pattern index. Photo by Kathy Hunt, University of Maryland

Buckeye Gala and Ultima Gala

Many of the red Gala fruit we spot picked in commercial orchards in Adams County were 100% red. That made it difficult to judge their ground color. While they have good red color, fruit in our sample blocks is still small. We again noticed a relatively-low seed count in these fruit. The Ultima Gala have lost much of their starch. Their tree ripening can be seen in the change in their starch pattern index.

To measure the starch pattern index (Photo 1), fruit are cut at the equator and then dipped into a brown-colored solution of iodine/potassium iodide for one minute. About five minutes after taking the apples out of the solution, the blue staining pattern is rated using the Cornell Starch Chart. Photo by Kathy Hunt, University of Maryland

A week ago the spot-picked Ultima Galas had a starch pattern index (SPI) of 4.8. In one week this increased to 6.6 which is approaching tree-ripe maturity. About ten percent of the Ultima Gala fruit we sampled had stem-end cracking. Individual Gala fruits with cracks typically had an SPI of 7 or 8 while sound fruit from the same block had an SPI of 5 or 6.

Honeycrisp

No data are shown this week for Premier Honeycrisp. The trees we sampled earlier this month have been harvested and marketed. Honeycrisp fruit has better size, but much less red color development than the Galas we tested.

The ground color of the Honeycrisp fruit was not as green as last week. Uneven maturation of Honeycrisp makes this a spot-pick variety. While most the fruit sampled were starchy and acidic, some had already lost most of their starch (See photo). Based on the variability we noticed, a first picking in the tops of Honeycrisp trees should begin soon.

With this year's early bloom, many people have been expecting an earlier harvest. The good news is size and color are excellent, and growers will not need to delay harvest. Remember, fruit going into long-term storage should not be tree ripe. When tree-ripe apples are stored for a long period, they may look good when they come out of storage but may be too soft to be packed.

Here is a brief summary of the data from our fourth week's samples:

CultivarDiameter (inches)Red Color (%)Ground ColorFirmness (pounds)Soluble Solids (°Brix)
Buckeye Gala (8/22)390Whitish Yellow21.513.2
Ultima Gala (8/22)380Whitish Yellow18.212.1
Honeycrisp (8/22)3.625Yellowish Green1612.9

Photo 2: Fruit color and starch staining pattern of representative samples of Buckeye Gala (Upper) and Ultima Gala (Lower) apples harvested on August 22, 2017 in Adams County, Pennsylvania. The loss of starch in the core and flesh regions was more pronounced in Ultima Gala. One Ultima Gala fruit at the bottom of the photo has stem end cracking and was also devoid of starch. Photo by Kathy Hunt, University of Maryland

Photo 3: Fruit color and starch staining pattern of representative samples of Honeycrisp apple fruit harvested on August 22, 2017 in Adams County. The great variability in the starch staining pattern in the Honeycrisp apples is typical of the spot-picked fruit we sampled. Photo by Kathy Hunt, University of Maryland.

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