Impact of varietal diversity and cooking on plantain banana phenolic compounds

The Musa germplasm presents a large genetic diversity including numerous edible Musa species. In particular, the fruit of plantain, a cooking banana, is a pillar of the food security in Central and West Africa. The demand for this food increases with the growing population. Moreover, plantain bananas are also traditionally involved in the healing of many health disorders such as stomach ulcer, wound, diabetes, hypertension, dysentery and typhoid. However, knowledge on the bioactive compounds such as phenolic compounds, which could contribute to these health benefits, is lacking in the literature. The strategy employed in the present study was first to characterize physico-chemical attributes of the fruit according to the diversity of edible Musa species and to the plantain ripening stages. This was accomplished by applying multivariate methods on the physicochemical characteristic data gathered through the analysis of the fruit. The contribution of the total phenolic compounds was evaluated. Secondly, the specific phenolic compounds of plantains were identified by high performance liquid chromatography coupled with a high resolution mass spectrometry with electrospray ionisation (HPLC-ESI-HR-MS) and used to characterize the diversity within plantain cultivars. The fate of the identified phenolic compounds was further determined after the boiling process. The pulp total phenolic compounds were among the most contributing attributes involved in the differentiation between cultivar groups built on the basis of the consumption mode and genomic constitution. This parameter separated the monospecific cultivars from the interspecific cultivars within dessert bananas as well as within cooking bananas. Physico-chemical attributes commonly recorded in post-harvest analyses of edible Musa fruit, together with pulp and peel total phenolics, were used to build ripening stage prediction models with interesting fitting parameters. The assessment of the specific phenolic compounds of plantain pulp and peel revealed that the pulp phenolic profile was dominated by hydroxycinnamic acids whereas the peel was dominated by flavonols. Ferulic acid-hexoside was the most important hydroxycinnamic acid in the pulp (4.4-85.1 µg / g dry weight) while rutin was the most abundant flavonol in the peel (242.2-618.7 µg / g dry weight). Hydroxycinnamic acids appeared to be the most contributing compounds involved in the differentiation between plantain cultivars. The pedo-climatic conditions could impact the phenolic profile of the pulp and the peel but further investigations need to be done on this issue. The effect of the boiling treatment on plantain phenolic compounds was tissue specific. Pulp total phenolics were well preserved after boiling with or without the peel whereas peel total phenolics drastically decreased after the boiling. An increase in ferulic acid monomers suggested a release from the cell wall or other polymeric components. This phenomenon was more intense in the peel than in the pulp. All the flavonols decreased with maximum losses of 61.3 % and 59.8 % obtained for kaempferol-rutinoside and rutin, respectively, for the cultivar Red Yade. Overall, this work contributes to a better knowledge of the phenolic composition of the edible Musa fruit and particularly of plantain. We showed that plantain bananas are good sources of phenolic compounds, which could be involved in the reported health benefits. In addition, the relevance of the pulp and peel phenolic profile to describe plantain diversity might be very useful for the breeders in the plantain field. Finally, the high flavonol content of the peel should stimulate this uneaten part of the fruit to be considered as a new source of bioactive compounds for food and pharmaceutical industries.(AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 201