Authors: Ioana M. Bodea | Alberto Garre Pérez | Giorgiana M. Cătunescu | Alfredo Palop
Source: Food and Bioprocess Technology (review, 2025-06-11)
Field: Chemistry — Analytical Chemistry

A Review on Microwave and Ultrasound-Assisted Extractions of Essential Oil from Orange Peel Waste Abstract Oranges are consumed globally, being widely appreciated for their nutritional benefits. Oranges embrace up to 53% of waste produced per year in the citrus industry, and most of the orange waste is destroyed because of its low nutritional value. But this problem could be overcome by extracting valuable compounds from orange waste and further using these compounds because of their bioactive nature. Orange essential oils are bioactive substances located mainly in the orange peel and have gained increased attention lately, being frequently utilized in the food, cosmetic, and pharmaceutical industries. Increased efforts have been made in finding efficient extraction methods of this valuable product. Novel effective, economic, and environmentally friendly extraction methods are needed for essential oil recovery, with minimal impact on the extracted yield and quality. Thus, this review critically assessed recent developments and improvements in the extraction of essential oil from orange waste by two innovative non-thermal methods: microwave and ultrasound-assisted extractions. The effectiveness in terms of cost, time, and energy consumption was assessed in comparison to conventional extraction methods (hydro-distillation, cold pressing, and steam distillation). The process parameters of the extraction methods and their effect on the yield and chemical composition of extracted essential oil were also studied, as this information could guide future efforts towards optimizing these technologies. Additionally, the challenges and future applications of microwave and ultrasound-assisted extractions techniques are also critically presented. Both microwave and ultrasound extractions showed improvements in terms of yield (11.5% vs 3.6%), cost, extraction time (30 min vs 180 min), carbon dioxide emission (160 g vs 2400 g), and energy saving (0.2 kW·h vs 3 kW·h) compared to conventional methods. However, there is a lack of implementation scenarios of these non-conventional techniques at industrial scale, as most studies were performed only at laboratory level. Thus, further research is needed for both microwave and ultrasound extractions to enable an effective transition toward large-scale implementation. Nonetheless, the main findings of this review are relevant to both research academics and industry professionals in research and development activities. This review offers critical insights that may advance applied research beyond the current state of the art by exploiting new approaches suitable for essential oil extraction. Additionally, it brings structured information to researchers supporting informed decision-making when selecting the most suitable essential oil extraction method for adding value from a by-product that is otherwise wasted. Orange (colour) ; Microwave ; Chemistry ; Pulp and paper industry ; Essential oil ; Ultrasound ; Food science ; Waste management ; Engineering ; Acoustics ; Physics Spectroscopy and Chemometric Analyses ; Essential Oils and Antimicrobial Activity ; Edible Oils Quality and Analysis