Contribution of microwaves or ultrasonics on carvone and limonene recovery from dill fruits (Anethum graveolens L.)

The objective of this study is to investigate alternative preparation techniques such as microwave and ultrasound for the recovery and evaluation of carvone and limonene from flaked dill fruits (Anethum graveolens L.). The study indicates that microwave-assisted extraction using hexane is highly recommended to reveal the correct amount of carvone and limonene in dill fruits. In this respect, when hexane is used, microwave-assisted system gives a better carvone yield of 29.96mg/g compared to 24.54 and 23.49mg/g for ultrasound and maceration (control) methods respectively. Furthermore, systems using hexane are able to recover high amount of limonene as opposite to systems using water where extracts are characterised by an absence of free fatty acids and a high abundance of carvone translated by high carvone/limonene ratio especially in microwaves (22.88) and ultrasound (6.55). These findings suggest that the intervention of microwaves or ultrasonics enhances extraction selectivity for carvone but have no great effect on limonene recovery. Although the recovered quantity of carvone in water extracts is much lower than the system using hexane due to low solubility of carvone in water, the advantages of using a GRAS solvent such as water are evident. It allows extracts to be readily available for spray application on potatoes' storage. In addition, the proposed enhancement involving ultrasound pre-treatment has helped in increasing carvone yield and has the advantage to be easily implemented on existing extraction processes. Our study shows that new technologies such as ultrasound and microwaves offer important advantages over conventional methods, such as shorter extraction time, energy saving and selectivity. Furthermore, the pretreatment of samples with ultrasound stands an intelligent tool to enhance extraction yields without jeopardising selectivity. Those aspects are of primary importance for industry to reduce cost and bring greener routes to their established processes. In another aspect, the application of the proposed tandem method involving ultrasonics and water as a solvent would contribute to the creation of a niche market for hydrocarbon-free products, which are very sought after from exigent clients. In addition, the results indicate also that water gives valuable advantages in terms of safety, cleanliness and adoption if we decide to generalise its use at an industry scale for carvone recovery. On top of that, using water as solvent in microwave