Solvent selection for efficient phenolic extraction from palm kernel cake using microwave-assisted techniques

This study investigated the recovery of phenolic compounds from palm kernel cake (PKC) using microwave-assisted extraction (MAE), focusing on the effects of solvent type and liquid-to-solid ratio on extraction efficiency. MAE was performed under constant microwave power (300 W) and extraction time (25 minutes), while varying the solvent types (ethanol, methanol, and water) and liquid-to-solid ratios (20:1, 30:1, and 40:1). Among the solvents tested, ethanol achieved the highest extraction yield (45%) and total phenolic content (TPC) of 0.086 mg GAE/g dry oil, while water produced the lowest yield (10%) and TPC (0.052 mg GAE/g dry oil). Regarding the liquid-to-solid ratio, the highest extraction yield (48%) was observed at a 40:1 ratio. However, the highest TPC was obtained at a 30:1 ratio, emphasising the dilution effect at higher solvent volumes. These findings demonstrate that optimising both solvent selection and liquid-to-solid ratio is critical for maximising phenolic recovery from PKC. Moreover, the use of ethanol, a food-grade and biodegradable solvent, coupled with MAE technology, provides a sustainable and cost-effective approach for the valorisation of agricultural by-products. The optimised process offers potential applications in the food, nutraceutical, and pharmaceutical industries.