Dewatering and Extraction of Hydrophilic Solutes and Essential Oils from Cryopreserved Lemon Peels Using Liquefied Dimethyl Ether

In general, dewatering of plant tissues (such as vegetables) and food materials is achieved by heating. In order to prevent the degradation of biologically active components in plant materials, the dewatering process should be carried out at low temperature. Therefore, in the present study, we attempted to develop a simple protocol for dewatering cryo-preserved plant tissues using liquefied dimethyl ether (DME). Prior to dewatering from frozen plant materials, we have examined the efficiency of liquefied DME for cryogenic removal of water from ice cubes. Here, lemon peel residue (consisting of flavedo and albedo) was chosen as the model plant material for dewatering and concomitant extractions of water-soluble components such as ascorbate and citric acid and hydrophobic components, chiefly, essential oils (EOs). By focusing on the exploitation of unused resources after food processing, the juice extraction residues from lemon fruits (lemon peels) were used as the starting materials. The yield of vitamin C (VC) extracted from the peel tissues derived from a single lemon fruit exceeded the amount of VC found in the manually press-extracted juice from a single lemon fruit. The major components in DME-extracted crude lemon EOs were determined and quantified with gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detector (GC-FID) to be limonene (40.4%, w/w), beta-pinene (10.4%, w/w), and gamma-terpinene (6.9 %, w/w).