Glucide Factors of the Inflorescence Sap of Four Coconut (Cocos nucifera L.) Cultivars from Côte D’ivoire

Abstract

Aim: To assess physicochemical characters related to the glucide contents of the sap provided by four coconut cultivars.   Study Design: Thirty-six coconut saps from thirty-six healthy coconut trees inflorescences, replicated two times. Trees were randomly selected; cultivars were the most widespread coconut types in Côte d’Ivoire. The whole coconut saps consists of three batches of three samples per cultivar. Place and Duration of the Study: Station Marc Delorme for the coconut Research at Port Bouet, National Centre of Agronomic Research (CNRA) of Côte d’Ivoire during 2012 and 2013. Methodology: Inflorescences saps from four coconut cultivars namely Malayan Yellow Dwarf, West African Tall, and PB 121+ and PB 113+ hybrids were investigated according to their carbohydrate content. Nine coconut trees were randomly selected per cultivar on experimental fields and their unopened inflorescences (spathes) of rank 8 have undergone the production of sap. The sap was harvested twice a day and samples from both harvestings were stored at -20ºC. Even quantities of the daily samples were mixed and a slight volume was taken from this mixture for analysis. Five traits (pH, contents of total soluble solids, dry matter, total soluble sugars and reducing sugars) related to glucidic richness of the coconut sap were assessed. Then the main carbohydrates components (sucrose, glucose, fructose, mannose and glycerol) were elucidated using a high performance ionic chromatography and led to the evaluation of the sweet index. Results: The effect of coconut cultivars on the pH and contents of total soluble solids, dry matter, total soluble sugars, sucrose, mannose, glycerol and sweet index was significant at P = .05. The sap of MYD recorded highest means of pH (7.32). This type of sap contained also highest contents of total soluble solids (16.31%), dry matter (16.47g/100ml), total soluble sugars (16.08g/100ml), mannose (0.019g/100ml) and glycerol (0.094g/100) contents and provided the greatest sweet index (16.00). Sucrose was the main carbohydrate of coconut sap. The MYD obtained higher sucrose content (12.24g/100ml) than the WAT (9.40g/100ml). Hundred (100ml) of saps from PB 121+ and PB 113+ provided respectively 10.31g and 10.38g of sucrose, which intermediate both means above. The contents of reducing sugars, glucose and fructose were respectively between 2.41 and 3.73g/100ml; 1.63 and 1.84g/100ml and from 1.24 to 1.52g/100ml, but didn’t differentiate saps originating with MYD, WAT, PB 121+ and PB 113+ cultivars. Reducing sugars were significantly composed of glucose (r = 0.83) and fructose (r = 0.91). Conclusion: The richness in glucides of coconut inflorescence sap is related to the contents of total soluble solids, dry matter and the whole carbohydrates. Thanks to their higher sucrose, glucose and fructose contents, the saps of the MYD, PB121+ and PB113+ cultivars could be suitable for the production of syrup, sugar and alcohol in order to improve benefits derived from the coconut.