Apple Maturity Assessments 2022: Red Delicious Week 9
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On our ninth week of evaluating fruit apple maturity, we started evaluating Red Delicious fruits harvested from Federalsburg, MD. None of these fruits have received any plant growth regulator. Red Delicious fruits are ready to be harvested for mid to short-term storage, as they are displaying 65% of red coloration, firmness values ~16.5 lbs, flesh starch disappearance values of 3.5 as well as soluble solids contents of 12%. Red Delicious is a cultivar that presents high susceptibility to harvest drop, thus it is important to harvest at the right time to avoid further losses. We also observed presence of moldy core in this cultivar, as expected, due to its known susceptibility to it. The information is summarized in Table 1.
Color
Surface color (eye-balling): Delicious fruits are presenting ~65% of red coloration.
Background color (DA index): Red Delicious fruit is presenting high values of ~1.6, typical of this cultivar. Readings of 0.6-0.7 are recommended for harvesting fruits for long-term storage, while an index of about 0.35 is targeted for harvesting fruit for short-term storage. 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: Red Delicious fruits are displaying firmness values of ~16.5lbs this week. In general, Red Delicious apples that are destined for long-term storage (>3 months) should be harvested with a firmness of at least 18lbs; while for fruit for mid- or shorter-term storage (1-2 months) a firmness of 16 - 17lbs is appropriate. Firmness was measured with a penetrometer with a 7/16-inch diameter plunger.
Starch
Starch content: Red Delicious fruits are displaying values of ~3.5. 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 3.5-5 are recommended for harvesting apples for storage, while 6-7 for fresh market.
Sugars and Acids
Soluble solids contents (SSC): SSC values, measured with a portable refractometer, are showing values of ~12.0% for Red Delicious. In general, it is recommended to harvest fruits with readings around 12% to 14% SSC.
Acidity: Red Delicious acidity values are ~0.35, characteristic of this cultivar. 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. Table 1 Summary table of maturity assessments for Red Delicious harvested from Federalsburg, Maryland.
| Location |
Federalsburg, MD |
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| Cultivar |
Red Delicious |
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| Date |
19 Sep |
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| Rootstock |
Unknown |
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| Diameter (in) |
3.0 |
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| Skin Red Color (% blush) |
65 |
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| DA Index |
1.6 |
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| Firmness (lbs) |
16.5 |
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| Starch Index (Cornell 1-8) |
3.5 |
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| Soluble Solids (%) |
12.0 |
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| Acidity (% Malic Acid) |
0.35 |
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Federalsburg, MD
Red Delicious
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Macarena Farcuh is an Assistant Professor of Horticulture in the Department of Plant Science and Landscape Architecture. She is interested in investigating how to develop novel strategies for improving fruit quality, nutritional value, shelf-life capacity, safety and marketability throughout fruit development, harvest and postharvest storage. Macarena’s research program integrates diverse approaches, including systems biology, physiology, biochemistry, analytical chemistry, molecular biology, and sensory science. Her goal is to contribute to decrease fruit loss/waste, support environmental sustainability and, at the same time, enhance fruit consumption by meeting consumers’ expectations and thus improve the health and well-being of populations.
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Haley Sater is an agricultural extension agent for Wicomico County specializing in fruit and vegetable production. She is interested in connecting with produce growers across Maryland to identify and promote profitable and sustainable fruit and vegetable systems. Her background is in small fruits and plant breeding.
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Contact Us: Macarena Farcuh, Ph.D.
Assistant Professor and Extension Specialist
University of Maryland, College Park
Email: mfarcuh@umd.edu
or
Haley Sater Ph.D.
Wicomico County Extension Educator
Wicomico County Extension Office
28647 Old Quantico Rd, Salisbury
Email: hsater@umd.edu
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The University of Maryland, College of Agriculture and Natural Resources programs are open to all and will not discriminate against anyone because of race, age, sex, color, sexual orientation, physical or mental disability, religion, ancestry, or national origin, marital status, genetic information, or political affiliation, or gender identity and expression.
Los programas del Colegio de Agricultura y Recursos Naturales de la Universidad de Maryland están abiertos a todos y no discriminará contra nadie debido a raza, edad, sexo, color, orientación sexual, discapacidad física o mental, religión, descendencia, origen nacional, estatus matrimonial, información genética, afiliación política, o identificación y expresión de género.
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