Combined Effect of Drying Method and Extraction Solvent on Ultrasound-Assisted Recovery of Ferulic Acid from Banana and Pomegranate Peels

Introduction

The increasing generation of fruit processing by-products has stimulated the search for sustainable strategies for their valorization into high-value bioactive compounds. Banana and pomegranate peels are abundant lignocellulosic residues rich in ferulic acid, a phenolic compound with antioxidant, antimicrobial, and anti-inflammatory properties. The recovery of ferulic acid depends not only on the extraction technique and solvent but also on sample pretreatment. Drying influences plant tissue structure and phenolic stability, thereby affecting extraction efficiency. Ultrasound-assisted extraction (UAE) is considered a green extraction technology due to its reduced solvent consumption, shorter extraction time, and enhanced mass transfer.

Methods

The influence of drying method and extraction solvent on the UAE recovery of ferulic acid from banana and pomegranate peels was investigated. Samples was subjected to convective drying at 50 °C and 70 °C or freeze-drying prior to extraction with ethanol or methanol under identical UAE conditions. Ferulic acid concentration (FAE) was quantified spectophotometricaly. Extraction yield, total phenolic content, antioxidant activity, pH, electrical conductivity, total dissolved solids, and color were determined.

Results

Pomegranate peel showed substantially higher ferulic acid recovery than banana peel under comparable UAE conditions. The highest FAE values were obtained after freeze-drying, reaching 14.02 µg/g_d.m. in pomegranate peel compared with approximately 1.11 µg/g_d.m.  in banana peel, while convective drying at the higher temperature resulted in considerably lower recovery. Methanol was particularly effective for freeze-dried pomegranate peel, whereas the influence of solvent was less pronounced for banana peel. Overall, the results demonstrate that both drying pretreatment and solvent selection strongly affect UAE performance, with pomegranate peel exhibiting markedly greater potential as a source of extractable ferulic acid.

Conclusions

Overall, drying pretreatment and solvent selection strongly influenced ferulic acid recovery, with pomegranate peel showing markedly greater extraction potential than banana peel. The results highlight the importance of integrating appropriate drying and extraction conditions to maximize the recovery of valuable phenolic compounds from fruit-processing residues. These findings contribute to the development of sustainable valorization strategies for agro-industrial by-products within a circular bioeconomy.