Physiological changes in relation to growth and ripening of khirni [Manilkara hexandra(Roxb.) Dubard] fruit

Abstract

Introduction. Fruit ripening is the process resulting in changes in color, taste and texture, which make the fruit acceptable for consumption. Since a wide spectrum of physiological, biochemical and organoleptic changes are involved in the development of a soft, edible, ripe fruit, we studied theses changes in an underutilized fruit, khirni [Manilkara hexandra (Roxb.) Dubard]. Materials and methods. The changes in biochemical composition, which includes chlorophylls, carotenoids, anthocyanins, sugars, starch, free amino acids, phenols and proteins, and the specific activity of enzymes such as amylase, invertase, catalase, peroxidase, pectinmethylesterase, polygalacturanase and cellulase were analyzed in the fruit of Manilkara hexandra at five sequential developmental stages (young, premature, mature, preripened and ripened fruit stages). Results and discussion. The pulp of khirni fruit tastes sour during its growth period, but turns sweet when it ripens. A decreasing trend in chlorophylls occurs simultaneously with an increase in the quantity of total carotenoids and anthocyanins. Further, an increase in the quantity of sugars, proteins and phenols occurs towards the ripened stage, but starch and total free amino acids show a decrease in their quantities. Also, khirni fruit exhibits climacteric behavior with its increased rate of respiration and ethylene production. The moderate to significant changes in the activity of enzymes such as amylase, invertase, catalase and peroxidase involved in a number of catabolic and anabolic reactions indicate that these enzymes also have an active role in the process of khirni fruit growth and ripening.