Valorization of rejected plantain fruit as an isomaltooligosaccharides syrup

Abstract

Introduction. The generation of agricultural waste, in particular from plantain fruit, have been increasing. Its accumulation and poor valorization limits the environmental, economic and social development of communities. The main goal of this work was to characterize physicochemically and functionally the flour obtained from rejected DominicoHartón pulp (Musa AAB Simmonds). As well as to evaluate the production of a prebiotic isomaltooligosaccharides syrup from this waste feedstock. Methodology. Moisture, total protein, ethereal extract and ash contents of the raw flour were determined applying AOAC methods. Thermal properties of the raw flour were determined through rheometry, differential scanning calorimetry and thermogravimetric analysis. The functionality and kinetics hydrolysis of the raw and cooked flour was evaluated by in vitro gastrointestinal digestion using the INFOGEST protocol. The production of isomaltooligosaccharides was made from plantain flour solution 18% (p/p) that was treated with thermostable -amylase at 95 ºC for 3 h. Starch dextrins were then treated with -amylase (barley) and pullulanase at 50 ºC for 24 h. Finally, the syrup was treated with -glucosidase (transglucosidase) at 50 ºC for 24 h. Saccharides were analyzed by HPLC. Results. Moisture, total protein, ethereal extract and ash contents determined for the flour were 9.8±0.5%, 2.83±0.01%, 0.46±0.03% and 2.15±0.02%, respectively. Starch and amylose content was 87±2% and 31.2 ± 0.8%, respectively. The pasting temperature, gelatinization temperature, gelatinization enthalpy, mass loss at the first decomposition stage and mass loss at the second decomposition stage were 79.26±0.02 ºC, 69.9±0.24 ºC, 2.48±0.04 J×g-1, 10.79±0.04% and 59.3 ± 0.1%, respectively. When cooked, the starch content changed for rapid (0.5±0.1 to 2.4±0.3), slow (15.6±1.2 to 32±1) and resistant digestion (59±1 to 48±2). The glycemic index predicted for raw and cooked flour was 47.7±2.2 and 84.2±1.8, respectively. The greatest amount of production of isomaltooligosaccharides was of degree of polymerization (DP) 3 (isomaltotriose) at 6 h of transglycosylation step, in a content of 25.75 g/L. Conclusions. The rejected plantain fruit showed potential as a prebiotic source, which may be a good strategy for the valorization of this waste.