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Modelling pH and titratable acidity in banana fruit based on acid and mineral composition

Bugaud C., Etienne A., Cazevieille P., Mbéguié-A-Mbéguié D., Lobit P.. 2013. In : Eds. H. Abdullah, M.N. Latifah. Proceedings of the Seventh International Postharvest Symposium, vol. 3, Kuala Lumpur, Malaysia, 25-29 June 2012. Louvain : ISHS, p. 1223-1228. (ISHS Acta Horticulturae, 1012). International Postharvest Symposium. 7, 2012-06-25/2012-06-29, Kuala Lumpur (Malaisie).

pH and titratable acidity are important indicators of banana fruit quality, since they are involved in the perception of sourness and sweetness. To understand which chemical components drive these parameters of acidity in banana pulp, they were modelled by solving a set of equations (conservation, dissociation, and ionic balance) representing acid/base reactions. The weak acids used in the model were malic, citric, oxalic, isocitric and phosphoric acids. Mineral cations taken into account were potassium and magnesium. The mineral anion chloride was taken into account as it neutralizes cations. The pH and titratable acidity were calculated based on the known acid and mineral composition of the 46 banana samples from 17 cultivars. The model was validated by comparing observed and calculated pH. The prediction of pH and titratable acidity by taking organic acids (malic, citric, oxalic, and isocitric acids), phosphoric acids, potassium, magnesium and chloride was insufficient. Adding a weak acid at a content of 1.5 meq 100 g-1 of fresh weight in the model considerably improved the prediction. The titratable acidity was best predicted with the same input data when titration endpoint was at a pH of 6.5 rather than at a pH of 8.1.

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