Valorization of banana inflorescence with integrated blanching and Taguchi-optimized ultrasound extraction

Abstract

Banana inflorescence (BI) is discarded as agricultural waste as it competes for nutrients with banana fruits. Despite containing valuable nutrients, naturally occurring polyphenol oxidase deteriorates its bioactive compounds, challenging its utilization. This article proposed a new valorization platform, including in-farm blanching and an optimized novel extraction methodology, aiming to extract phytochemicals from bracts and male flowers of BI. In this sense, power ultrasound, an emerging nonthermal technology, is compared with conventional solvent extraction while optimizing the extraction conditions using the orthogonal L9(3⁴) Taguchi method. Independent parameters were ultrasound power, solvent concentration, solid–liquid ratio, temperature, and time. Process optimization was followed by extract analysis, including total phenolic content (TPC), total flavonoid content (TFC), and antioxidant capacity (DPPH and ABTS radical scavenging activity). The highest TPC (8.76 ± 0.09 mg/g) for conventional extraction of banana bracts was obtained under 60% ethanol, 1:35 solid–liquid ratio, and 45 min of extraction at 50°C. At the same time, the highest TPC (50.64 ± 0.63 mg/g) of the male flowers was achieved with 40% ethanol, 1:35 solid–liquid ratio, and 45 min of extraction at 55°C. On the other hand, optimal ultrasound conditions were 150 W, 60% ethanol, and a solid–liquid ratio of 1:35 for 8 min, which yielded TPC of 9.43 ± 0.23 and 60.37 ± 0.54 mg/g for banana bracts and male flowers, respectively. Accordingly, ultrasound enhanced the extraction efficiency of bracts and male flowers by 7.6 and 19.2%, respectively, while saving substantial time (82.2%) compared to the conventional method. Besides, ultrasound-assisted extraction increased TFC by 1.29-fold. The findings highlighted the potential of BI as a rich resource for functional ingredients (e.g., for food and cosmetic industries) and the capability of the proposed integrated extraction approach to promote sustainability by utilizing and reducing agricultural waste to advance toward zero waste and more sustainable food production.