Determination of a colour index for fruit of pomegranate varietal group “Mollar de Elche”

Pomegranate acceptability by consumers and processors depends basically on a combination of several quality attributes, among them rind colour, sugar content, acidity and flavour. The pomegranate varietal group “Mollar de Elche” is one of the most highly valued worldwide because of its outstanding flavour and high antioxidant content. The aim of this study was to determine how the external colour of the fruit evolves from the young state to harvesting, focusing on obtaining a maturity index to provide growers with a cheap, rapid and non-destructive way of assessing the optimal time for harvesting. The colorimetric maturity index (MIc) proposed, which integrates the three colorimetric coordinates, L*, a* and b*, shows very little interannual variability. It also shows a high degree of correlation with the number of days elapsing since the beginning of fruit development, with fruit growth and with the chemical maturity index, permitting the period of fruit growth and ripening to be divided into four phases running from the beginning of fruit development (MIc < −20, immature very green fruit) until the time when fruit are ready for harvest (MIc > 25, mature reddish yellow or red fruit).The index proved to be robust, with little interannual variability and a high degree of correlation with the number of days since the beginning of fruit development, fruit growth and the evolution of the chemical maturity index, permitting growers to determine cheaply, non-destructively and objectively the optimal moment for harvesting the varietal group “Mollar de Elche”.

► Determination of a colour index for fruit of pomegranate.
► A strong correlation between the colorimetric coordinates and the maximum temperature.
► The colorimetric maturity index (MIc) integrate the three colorimetric coordinates, L*, a* and b*.
► Relation between colorimetric maturity index, chemical maturity index and fruit development.