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University of Maryland Extension &
Department of Plant Science and Landscape Architecture, University of Maryland, College Park

Apple Maturity Assessments 2022: Red Delicious and Fuji Week 11

We are entering our eleventh week of assessing fruit apple maturity. This week we continued assessing Red Delicious and Fuji fruits located in Federalsburg, MD and we also included Aztec Fuji from Smithsburg, Maryland. None of these fruits have received any plant growth regulator. This is the last week we evaluate Red Delicious fruits, as they are ready to be harvested for fresh consumption, displaying excellent red coloration (80% red color), firmness values ~15 lbs, flesh starch disappearance values of 6.0 and soluble solids contents of 13.5%. We also observed presence of moldy core in this cultivar, as expected, due to its known susceptibility to it. Fuji apples harvested from Federalsburg entered their harvest window this week, as they are displaying firmness values ~17 lbs, flesh starch disappearance values of 6.0 and soluble solids contents of 15.3%, although it is important to highlight that the red skin coloration values in this location were only ~45%. On the other hand, Aztec Fuji apples harvested from Smithsburg are still not ready for harvest, but very soon entering their harvest window. In contrast to Federalsburg, Aztec Fuji from Smithsburg are displaying skin red coloration values ~60%. We have observed the presence of the physiological disorder of watercore starting to develop in Fuji’s from both locations. The information is summarized in Table 1.


Surface color (eye-balling): Red Delicious fruits increased since last week and are presenting ~80% of red coloration. Fuji from Federalsburg presents only ~45% of red color, while Aztec Fuji from Smithsburg is displaying ~60%.
Background color (DA index): Red Delicious decreased its values to ~1.2 this week, which are still high but are typical of this cultivar. Fuji fruits are displaying values of 1.1-1.2 from both assessed locations. Fruits were measured with a DA meter, a device that measures the absorbance difference between 670nm and 720nm light. A higher DA index indicates a larger content of chlorophyll-a in the fruit skin.


Fruit firmness: Red Delicious fruits decreased their firmness to 15 lbs, while Fuji fruit from Federalsburg displayed firmness values of ~17 and Aztec Fuji from Smithsburg presented the highest flesh firmness values of ~18 lbs. In general, Red Delicious and Fuji apples that are destined for long-term storage (>3 months) should be harvested with a firmness of 18 lbs; while for fruit for mid- or shorter-term storage (1-2 months) a firmness of 16 - 17 lbs is appropriate. Firmness was measured with a penetrometer with a 7/16-inch diameter plunger.


Starch content:    In the case of Red Delicious and Fuji apples from Federalsburg, they both presented values ~6.0, increasing (meaning an increase in starch disappearance) since last week. In the case of Aztec Fuji from Smithsburg, the values are ~4.0. 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 ~13.5% for Red Delicious. Fuji apples are showing high values in the range of 15-15.5% for both locations, which are typical of this cultivar. In general, it is recommended to harvest fruits with readings around 12% to 14% SSC.

Acidity In the case of Red Delicious acidity values decreased <0.2, characteristic of this cultivar; while Fuji fruits from both locations are displaying values in the range of 0.4-0.45, with Smithsburg apples located in the higher range. 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 Red Delicious and Fuji harvested from Federalsburg, Maryland and Aztec Fuji harvested from Smithsburg, Maryland. Values in parentheses indicate the results from last week’s monitoring. 
Location Federalsburg, MD Federalsburg, MD Smithsburg, MD
Cultivar Red Delicious Fuji Aztec Fuji
Date 3 Oct  3 Oct 4 Oct
Rootstock Unknown Unknown G11
Diameter (in) 3.0 (3.0) 3.0 (3.0) 3.4 
Skin Red Color (% blush) 80 (70) 45 (40) 60
DA Index 1.2 (1.4) 1.1 (1.3) 1.2
Firmness (lbs) 15.0 (15.8) 17 (18) 18
Starch Index (Cornell 1-8) 6.0 (4.5) 6.0 (4.5) 4.0
Soluble Solids (%) 13.5 (13.0) 15.3 (15.0) 15.5 
 Acidity (% Malic Acid) 0.17 (0.2) 0.4 (0.45) 0.45

Fruit View

Federalsburg, MD
Red Delicious

Federalsburg, MD 

Smithsburg, MD 
Aztec Fuji

Meet the Team
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.
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. 
Contact Us: Macarena Farcuh, Ph.D.
Assistant Professor and Extension Specialist
University of Maryland, College Park


Haley Sater Ph.D.
Wicomico County Extension Educator 
Wicomico County Extension Office
28647 Old Quantico Rd, Salisbury
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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