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On our thirteenth week of apple fruit maturity assessment report, we continued to evaluate Evercrisp on G11 from Smithsburg, MD and added Cripps Pink fruits from this same location. None of these fruits have received any plant growth regulator. Evercrisp fruits are displaying values indicating they are starting to enter their harvest window by this week, as they are displaying >70% of red coloration, firmness values ~19 lbs, increased their flesh starch disappearance values to 5.0 as well as their soluble solids contents to >17.0%. We have continued to observe the presence of the physiological disorder of watercore in Evercrisp apples, which increases as the fruit advances in maturity (but most will dissipate in storage). Cripps Pink apples, as expected, are still not ready to harvest. Although the red skin color is ~55%, they are still displaying high flesh firmness values (~21 lbs), high DA values (~1.1.), and starch disappearance values of ~2.0. The information is summarized in Table 1.
Color
Surface color (eye-balling): Evercrisp fruit are presenting > 70% of skin red color, while Cripps Pink is presenting low values of ~55%.
Background color (DA index): Evercrisp decreased its values to ~0.7 this week, with respect to the 0.8 that we had reported last week. Cripps Pink fruits are displaying high values still of ~1.1. Fruits were measured with a DA meter, a device that measures the absorbance difference between 670 nm and 720 nm light. A higher DA index indicates a larger content of chlorophyll-a in the fruit skin.
Firmness
Fruit firmness: Evercrisp fruits have maintained their high firmness values, and this week of evaluation are still ~19 lbs. It is known that firmness is not an issue with this cultivar, but it should be harvested with values no lower than 17 lbs. Cripps Pink are displaying flesh firmness values of ~21 lbs. Firmness was measured with a penetrometer with a 7/16-inch diameter plunger.
Starch
Starch content: Evercrisp increased its starch disappearance from what we measured last week and is now displaying values of ~5.0. Cripps Pink fruits are displaying values of ~2.0, thus indicating a high presence of starch in the fruit. The common starch index rating system (Cornell chart) on a scale from 1 to 8, where 1 is full starch (all blue-black) and 8 is starch-free (no stain), was used. In general, on a 1 to 8 scale, values ranging from 5-6 are recommended for harvesting Evercrisp apples for storage.
Sugars and Acids
Soluble solids contents (SSC): SSC values, measured with a portable refractometer, are showing an increase in values for Evercrisp from ~17.0 to ~18%, characteristic of this cultivar. It is worth indicating that we observed the presence of watercore to continue to develop in this cultivar. In general, it is recommended to harvest Evercrisp fruits with readings > 16% SSC. Cripps Pink are displaying values of 13.5%.
Acidity: Evercrisp and Cripps Pink fruits are displaying acidity values of ~0.7 and ~0.6, respectively. A decrease in acidity content is an indicator of advancing maturity, reason why this indicator is included in this report. Acidity was measured with an automatic titrator, quantifying malic acid (the major acid present in the juice of apples).
Table 1. Summary table of maturity assessments for Aztec Fuji and Evercrisp harvested from Smithsburg, Maryland. Values in parentheses indicate the results from last week’s monitoring.
| Location |
Smithsburg, MD |
Smithsburg, MD |
| Cultivar |
Cripps Pink |
Evercrisp |
| Date |
18 Oct |
18 Oct |
| Rootstock |
G11 |
G11 |
| Diameter (in) |
3.0 |
3.6 (3.6) |
| Skin Red Color (% blush) |
55 |
75 (73) |
| DA Index |
1.1 |
0.7 (0.9) |
| Firmness (lbs) |
21 |
19.0 (20.0) |
| Starch Index (Cornell 1-8) |
2.0 |
5.0 (2.0) |
| Soluble Solids (%) |
13.0 |
17.8 (17.0) |
| Acidity (% Malic Acid) |
0.70 |
0.62 (0.70) |
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