Assessing Apple Fruit Maturity in 2017

This is the second year of a grower-funded project to routinely assess fruit starch levels, ground color, and other maturity indices.
Assessing Apple Fruit Maturity in 2017 - News


Blush and ground color changes as fruit mature. Photo: Brianne Redman

This will allow growers to make improved decisions about optimum harvest dates for long-term storage. The Mid-Atlantic apple industry is going through a number of dramatic changes due to the planting of high density orchards with newer cultivars. These transitions, coupled with climate and weather changes, make it difficult for growers to predict optimum fruit maturity for long-term storage.

To track developments in physiological maturity, we will measure starch pattern, firmness, soluble solids, fruit size, % red color and ground color changes (visually and with a Delta A meter). The cumulative data will be updated weekly at Apple Maturity Assessments, and summaries of Starch Pattern Index and Delta A values will be posted weekly at Fruit Times.

Our working hypothesis is that ethylene--sometimes referred to as the fruit ripening hormone--increases as fruit mature, leading to the coordinated ripening of apples. Ethylene initiates new enzyme production in fruit that affects visible attributes like surface color and ground color, as well as hidden attributes like starch pattern index, flesh firmness and soluble solids.

The project is supported by the State Horticultural Association of Pennsylvania Research Committee and is a cooperative effort of University of Maryland Extension and Penn State Extension.