Abstract
The aim of this work is the optimization of phenolic compound extraction from three by-products of banana crops (rachis, discarded banana, and banana’s pseudostem pulp), as a way to valorize them through a green extraction process. The influence of the temperature and aqueous ethanol concentration (Et-OH) on extract properties (total phenol content (TPC) and antioxidant activity) was firstly analyzed. 78 ℃ and ethanol concentrations close to 50% yielded the best results for the three materials. The equations obtained by the response surface methodology gave a satisfactory description of the experimental data, allowing optimizing the extraction conditions. Under optimized conditions, time influence was then assessed, although this parameter seemed not influence results. Among the three by-products, rachis extract (60% Et-OH, 78 ℃, and 30 min) presented the highest TPC (796 mg gallic acid/100 g of dried material) and antioxidant activity (6.51 mg Trolox equivalents/g of dried material), followed by discarded banana, and pseudostem pulp. Under the optimal conditions, experiments were performed at a larger scale, allowing to determine the extraction yields (EY) and to characterize the extracts. The highest EY was obtained for the rachis (26%), but the extract with the highest activity was obtained for discarded banana (50% Et-OH, 78 ℃, and 60 min), which presented a TPC of 27.26 mg/g extract corresponding to 54.59 mg Trolox equivalents/g extract. This study contributes to the valorization of banana crops residues as a source of polyphenolic compounds with bioactive functions that can be extracted under economic extraction conditions.Graphical abstract
Highlights
The agricultural production and the agro-food industry produce large volumes of residues and their utilization for the production of value-added products has received much attention in recent years
Proximate analysis of rachis and banana’s pseudostem pulp (BPP), both of lignocellulosic nature, and banana reflected a high content in carbohydrates, upper than 50% for all the materials
Those differences can be attributed to real variations in the composition and to the protocols employed in the characterization, which reflects that the compositional analysis of biomass is still a challenging task [43] and that standardized protocols that minimize the errors resulting from the approaches assumed are needed
Summary
The agricultural production and the agro-food industry produce large volumes of residues and their utilization for the production of value-added products has received much attention in recent years. One example of it is the banana cultivation. Banana is cultivated over 130 countries and it is the second largest produced fruit, after citrus [1], with an estimated gross production exceeding 116 million tons [2]. Banana crops produce a great amount of wastes at the farming site (pseudostem, leaves, and inflorescences), because of the necessity of decapitation of the whole plant so that the young suckers can replace the mother plant, and at the processing sites (rachis and discarded bananas) where the fruit is packaged.
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