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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 10

We are entering our tenth week of assessing fruit apple maturity. This week we continued assessing Red Delicious fruits located in Federalsburg, MD and we also included Fuji from this same location. None of these fruits have received any plant growth regulator. Red Delicious fruits continued advancing their maturity, and this week they are ready to be harvested for short-term storage, as they are presenting 70% of red coloration, firmness values ~16 lbs, flesh starch disappearance values of 4.5 as well as soluble solids contents of 13%. Fuji apples are still not ready for harvest for storage, but very soon entering their harvest window. They are already showing high soluble solid contents ~15%, typical of this cultivar. The information is summarized in Table 1.



Surface color (eye-balling): Red Delicious fruits increased since last week and are presenting ~70% of red coloration, while Fuji presents ~40% of red color. 
Background color (DA index): Red Delicious decreased its values to ~1.4 this week, which are still high but are typical of this cultivar. Fuji fruits are displaying values of ~1.3. 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. Fruit 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.


Fruit firmness: In this second week of evaluation, Red Delicious fruits decreased their firmness to ~16 lbs, while in its first week of assessment Fuji displayed the highest flesh firmness values of ~18 lbs. In general, Red Delicious apples that are destined for long-term storage (>3 months) should be harvested with a firmness of at least 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 values are ~4.5 for both cultivars, with Red Delicious presenting an increase in values (meaning an increase in starch disappearance) since last week. 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 ~13.0% for Red Delicious. Fuji apples are showing high values of ~15%, which are typical of this cultivar. In general, it is recommended to harvest fruit with readings around 12% to 14% SSC.

AcidityIn the case of Red Delicious acidity values also decreased to ~0.2, characteristic of this cultivar; while Fuji fruits are displaying values of ~0.5 in this first week of assessment. 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. Values in parentheses indicate the results from last week’s monitoring. 
Location Federalsburg, MD Federalsburg, MD
Cultivar Red Delicious Fuji
Date 26 Sep 26 Sep
Rootstock unknown unknown
Diameter (in) 3.0 (3.0)  3.0
Skin Red Color (% blush) 70 (65) 40
DA Index 1.4 (1.6)  1.3 
Firmness (lbs) 15.8 (16.5)  18
Starch Index (Cornell 1-8) 4.5 (3.5)  4.5
Soluble Solids (%) 13 (12) 15.0
Acidity (% Malic Acid) 0.20 (0.35) 0.45 

Fruit View

Federalsburg, MD
Red Delicious

Federalsburg, MD 

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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