Postharvest biochemistry of the Plantain (Musa paradisiacal L.)

Abstract

ACC oxidase activity (ethylene production) in the peel and pulp was monitored over the ripening stages of the plantain (Musa paradisiacal L.). The activity of the enzyme in the peel increased from the hard green stage (0.36 ng ethylene h-1 g-1 Fw) and reached a maximum at the more green than yellow stage (21.99 ng ethylene h-1 g-1 Fw). There after the activity of the enzyme declined rapidly to 1.20 ng ethylene h-1 g-1 FW at the yellow with few brown patches stage. No enzyme activity was detected at the yellow with large brown patches stage. Similar results were obtained for the pulp. The enzyme was inhibited by sodium dithionite and sodium metabisulphite, 31.8 and 25.0%, respectively. The activity of β-D-galactosidase, β-D-glucosidase and N-acetyl-β-D-glucosaminidase was determined at the unripe, ripe and overripe stages of ripening in the plantain. β-D-galactosidase and β-D-glucosidase activity was greater in the pulp than in the peel when p-nitrophenyl-β-D-galactopyranoside and p-nitrophenyl-β-D-glucopyranoside were used as respective enzyme substrates. The reverse was true for N-acetyl-β-D-glucosaminidase (using p-nitrophenyl-N-acetyl-β-D-glucoaminiside as substrate); where more activity was detected in the peel than in the pulp at all the ripening stages. When o-nitrophenyl-β-D-glactopyranoside was used as the substrate for β-D-galactosidase more activity was detected in the peel than in the pulp. The cell wall degrading enzyme polygalacturonase showed more activity in the pulp than in the peel for all the ripening stages, with the activity increasing, going from the unripe stage (1.03 × 10-4 μmole galacturonate min-1 g-1 Fw) through to the over-ripe stage (4.5 × 10-4 μmole galacturonate min-1 g-1 Fw). Postharvest technology was performed on the plantain, at controlled atmosphere (CA) and regular atmosphere (RA). The production of ethylene under CA conditions (using the diffusion channel system) was not detected when compared to fruit kept at RA. The use of postharvest technology resulted in the enhancement of the shelf-life of the plantain when stored at CA. © 2007 Asian Network for Scientific Information.