Changes in Peel and Pulp Characteristics of Banana (Musa AAA ‘William Cavendish’) as Influenced by Ripening Temperatures

A study on the changes in peel (colour, chlorophyll and carotenoid content, chlorophyll oxidase activity and chlorophyll derivatives) and pulp ripening characteristics (firmness, soluble solids concentration, titratable acidity and pH) of banana (Musa AAA ‘William Cavendish’) were conducted. Five mature green banana fingers per polystyrene tray were induced to ripen using 1000µl/L ethylene gas. Five banana fingers per tray were wrapped with a plastic cling-wrap film. The film was then injected with syringe to induced ripening against the fruits using 1000µl/L ethylene gas. Masking tape was then used to prevent the gas from moving out from the tray. The tray containing the banana fruits was then kept in a ripening chamber at 18±2 and 27±2 °C. After 24 hour, the film was removed and the fruit was allowed to continue ripening in respective temperatures until day five of ripening. The experiment was conducted using a randomized complete block design (RCBD) with a factorial arrangement of treatments (2 ripening temperatures x 6 ripening days) with five replications. Data from measurements of the peel (colour, chlorophyll and carotenoid contents, chlorophyll oxidase activity and chlorophyll derivatives) and pulp ripening characteristics were analyzed using analysis of variance (ANOVA) and regression were done using general linear model (GLM) (SAS Institute, Cary, N.C., 1989). Treatment differences were separated using Duncan multiple range test (DMRT). Correlation analysis by means of Pearson’s correlation matrix was performed to establish the associations between each parameter. The peel colour, chlorophyll and carotenoid content, chlorophyll oxidase activity and chlorophyll derivatives of Cavendish were affected by the interaction between ripening temperature x ripening day. The results of this study showed that the combination of high L* and C* with low ho value produced light-vivid-yellow colour in peel of Cavendish banana ripened at 18±2°C (CBR18). However, peel of Cavendish ripened at 27±2°C (CBR27) produced dark-pale-green colour as indicated by low L* and C* combined with high ho value. The study showed that about 70% of the total chlorophyll content (total chl) had disappeared when Cavendish banana was ripened at 18±2°C and the banana peel attained bright yellow colour. However, total chl of CBR27 decreased by 27% as ripening progressed. There was no significant difference in the content of peel α and β-carotene of CBR18 and CBR27 at different days of ripening. A steady increase in the peel lutein was noted at both ripening temperatures. The activity of chlorophyll oxidase (chlox) increased both linearly and quadratically as ripening progressed from ripening day zero to ripening day five in CBR18 peel. However, the peel chlox of CBR27 had a significant linear decrease (R2 = 0.96) as fruit ripened. Chlorophyllide a (chlide a) increased as chlorophyll a (chl a) decreased with degreening of CBR18 peel. Chlide a in CBR18 seems to be degraded to pheophorbide a (phb a) as indicated by increasing in phb a, which is subsequently converted to colourless low molecular weight compounds. The results of this study also showed that chl a-1 increased as Chl a decreased. Results also indicated that the peel total chl, chl a and chl b of CBR18 had a significant positive correlation with ho value. There was significant correlation between peel colour values (L*, C* and ho) and peel carotenoid (α-carotene, β-carotene and lutein) in CBR18. The ho value of CBR18 had no significant correlation (r2 = 0.05) with chlorophyll oxidase activity. The results showed that ho value of peel CBR27 had a significant positive correlation with total chl (r2 = 0.53), chl a (r2 = 0.53) and chl b (r2 = 0.73). The peel ho value of CBR27 also showed significant positive correlation with peel carotenoid (α-carotene, β-carotene and lutein). The ripening characteristics (firmness, soluble solids concentration, titratable acidity and pH) of Cavendish pulp were affected by the interaction between ripening temperature x ripening day (RD). The pulp of CBR27 tended to be softer and sweeter than CBR18 as ripening progressed from RD0 to RD5.

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