Cold Pressing Citrus Oils

Such a system has been used for the comprehensive 2D chromatography of proteins [9,14], synthetic polymers [16], oxygen heterocyclic fraction of cold-pressed citrus oils [22,29], carotenoids [39], triglycerides in fats and oils [18-21], pharmaceuticals [29], and acidic and phenolic compounds [27,28]. 

Furanocoumarins Also called furocoumarins, methoxypsoralens or bergaptenes. Found in cold-pressed citrus oils, e.g. bergamot. An oxygen-containing cyclic structure associated with phototoxicity on exposure to ultraviolet light. 

Usually, the terpenes are removed from the cold-pressed oils (deterpenation) to concentrate the flavour fraction, thus resulting in a more stable product with improved solubility in the alcoholic solvents used in food and perfume processing. Supercritical carbon dioxide extraction appears as a promising and alternative technique to refine cold-pressed citrus oils [1,2, 3). Potentially, it has the advantages that it can be carried out at mild temperatures, provides better yields and leaves no solvent residues. 

Apart from the volatile constituents, cold-pressed citrus oils contain a non-volatile fraction in varying amounts (1% in orange oil, up to 10% in cold-pressed lime oil), which is associated with emulsifying and stabilising properties. 

In conclusion, it is possible to concentrate the flavor fraction of cold-pressed citrus oils with supercritical fluid technology by selectively extracting the terpenes from the oil. During continuous extractions, the amount of extract followed a linear trend with time over the first 5 hours of extraction and it increased five times when the flow rate was increased ten times. Since the design of supercritical fluid extraction and solvent regeneration processes for the concentration of citrus oils require accurate calculation of phase equilibria, more research must be done to determine the equilibrium solubility data, the thermod3mamic model to represent the system, and the economic feasibility of the process. 

Until the beginning of the twentieth century, industrial production of cold-pressed citrus oils was carried out manually. One has to visualize huge halls with hundreds of workers, men and women, seated on small chairs handling the fruit. First of all, the fruit had to be washed and cut into two halves. The pulp was then removed from the fruit using a sharp-edged spoon, called the rastrello, and after, the peel was soaked in warm water. The fruit peel was now manual turned inside out so that the epicarp was on the inside and squeezed by hand to break the oil glands, and the oil soaked... 

One of the best examples of the application of comprehensive NPLC x RPLC in essential oil analysis is represented by the analysis of oxygen heterocyclic components in cold-pressed lemon oil, by using a normal phase with a microbore silica column in the D and a monolithic C18 column in the with a 10-port switching valve as interface [133]. In Figure 7.12, an NPLC x RPLC separation of the oxygen heterocyclic fraction of a lemon oil sample is presented. Oxygen heterocyclic components (coumarins, psoralens, and PMFs) represent the main part of the nonvolatile fraction of cold-pressed citrus oils. Their structures and substituents have an important role in the characterization of these oils. Positive peak identi cation of these compounds was obtained both by the relative... 

All of these products are much inferior to cold-pressed citrus oils in both flavor and keeping properties. 

Cold-pressed essential oils from the peel are some of the most important by-products recovered during the processing of Citrus fruits. The presence of limonene in the aqueous discharges, with its antimicrobial activity [1], decreases the effectiveness of the waste treatment system and increases the time necessary for the biological breakdown of the organic matter produced in the peel oil recovery system [2,3]. Additional recovery of essential oils from waste water would increase industry s returns and reduce the pollution problems associated with the disposal of waste water [4,5]. Several methods for reducing the levels of residual essential oils in the aqueous effluent have been developed over the years [6-11]. 

The objectives of this study were to compare the yields of cold-pressed essential oil, water consumption, material balance and efficiency of the process in a typical citrus peel oil recovery plant with and without recycling system. The different emulsions and aqueous discharges from these processes were also characterized. 

Hunter and Brogden (1965) generated chromatograms that provide a visual representation of the various citrus oils. The GC conditions for the orange oils are similar, giving the same retention times but different peak ratios for the various hydrocarbons. Comparisons of cold-press Valencia oil from Florida versus Califor-... 

For flavones in citrus peel oils, separations were accomplished with isocratic mobile phases of 38% and 40% acetonitrile in H20 (1). The extracts of peel and cold-pressed peel oils were diluted in ethanol and analyzed by reversed-phase on various C18 columns with good results. For the dilute citrus oils, gradient elution was preferred, to prevent the accumulation of terpenes on the column. With normal-phase chromatography, the elution order is reversed terpenes elute with the solvent front and are not a problem. 

For coumarins in orange fruits (115), the HPLC used a Zorbax Rx C8 (250-mm X 4.6-mm ID, 5 fim) column maintained at 25°C, and analysis was performed by binary-gradient elution using 0.1% HOAc in acetonitrile (eluent A) and 0.1% HOAc in HzO (eluent B). In the author s lab, standard coumarins could be separated by isocratic elution on Zorbax Rx C8 column with acetonitrile-0.1% HOAc in water (35 65) at 1.0 ml/min, as presented in previous work (1). The eluate from the column was passed to a UV detector (UV 330 nm) and then into a fluorescence detector (excitation at 340 nm, emission at 425 nm). As for the specificity, some of the coumarins do not have native fluorescence. Nine coumarins are separated under UV 330 nm, and three coumarins could not be detected with fluorescence detection. Detailed conditions for coumarin analysis in foods and absorption spectra of coumarins obtained by online diode array detector with HPLC were presented by Lee and Widmer (1). Since coumarins exhibit strong absorption in the ultraviolet region, absorption at approximately 313 nm has been used to estimate the dilution of cold-pressed lemon oil with distilled oil (12). Analysis of umbelliferone (7-hydroxy-coumarin) and scopoletin (6-methoxy-7-hydroxycoumarin) in citrus fruits was performed using... 

A common practice to study each citrus oil is to consider it as a binary synthetic mixture of its two more important components [4, 5, 6, 7]. For instance, the cold-pressed orange oil is usually treated as a mixture of limonene and linalool, representing the terpene and the oxygenated fractions, respectively. 

Distillation of citrus juices yields two volatile fractions, namely, aqueous essences and essence oils that are separated from each other by condensation of the distillate (7). Aqueous essence, the bottom layer of the condensate is comprised of organic acids, alcohols, aldehydes, esters, hydrocarbons, ketones, hydrogen sulfide, and oxides (10). Considering many components found in both cold-pressed peel oil and aqueous essence, essence oil has a flavor similar to that of the combined peel oil and aqueous essence (10). However, essence oil usually contains a larger amount of... 

These compositional changes usually negatively influence the odor and flavor of citrus peel oils by generating off-flavor products. It has been shown that nonvolatile residues of citrus peel oil contain some compounds that exhibit antioxidative activities, among which permethoxylated flavones, dehydroabietic acid (46), coumarins, and psoralens have been identified (33). In this respect, cold-pressed citrus peel oil is more stable than distilled oil and essence oil, in which most of the natural antioxidants present are left behind when the oil is distilled (1). 

Distilled lime oils possess a terpeny-like, fresh, sharp citrus note, which characterises the cola flavour. Distilled lime oils are mainly used in soft drinks. Apart from flavouring colas, the combination lemon-lime has also found widespread application. Cold-pressed lime oil is well suited for usage in perfumery, as its fresh, heavy, sweet, earthy and peel-like smooth and balsamic citrus note possesses an exceptionally high sensorial potential and is, therefore, held in high esteem [65]. 

Supercritical fluid extraction is also a suitable technique for enhancing the quality of essential oils obtained by conventional extraction methods, by means of fractionation and deterpenation. Thus, the separation of citrus oils into different clssses of substances by supercritical CO2 has been widely investigated. Temelli et al. reported a method for the extraction of terpene hydrocarbons from cold-pressed Valencia orange oil with supercritical CO2, using both static and dynamic flow approaches (65). Another article has reported the SFE of terpenes from cold-pressed orange oil in a temperature range from 40°C to 70°C and pressures from 83 to 124 bar (66). The determination and elimination of psoralens from lemon peel oil by SFE has also been conducted (67). The procedure included the increase of CO2 density in successive steps. 

The (+)-enantiomer, main constituent of cold-pressed citrus peel oils, has a remarkably low odor threshold value of lOppb in water (Buttery et al., 1969b). This figure has been corrected to 200ppb for the (7 )-(+)-isomer and 500 ppb for the (S)-(—)-isomer, the error being due to impurities, very important for these low values (Buttery, 1999). Ahmed et al. (1978) estimated a probable odor threshold of 60 ppb and flavor threshold of 210ppb, but these were measured on a sample 96.5% pure. 

Citrus oil is present in small glands contained in the flavedo, which is the colored portion of the peel of the fruit. Cold-pressed citrus peel oil is obtained commercially by a process that starts with the rupture of these glands during juice extraction. For its recovery, the oil is washed away from the peel with water forming an... 

Colawet TDS-35. See Tetrasodium dicarboxyethyl stearyl sulfosuccinamate Cold Pressed Grapefruit Oil. See Grapefruit (Citrus grandis) oil... 

Cold Pressed Orange Oil, Cold Pressed Orange Oil, Brazilian. See Orange (Citrus aurantium dulcis) oil... 

Coriander (Coriandrum sativum) oil 8008-53-5 Ethiodized oil lodorga Phyt iod 8008-56-8 Citreatt Lemon 3123 Citreatt Lemon 6122 Lemon (Citrus medica limonum) oil 8008-57-9 Citreatt Orange 3111 Citreatt Orange 6110 Cold Pressed Orange Oil Cold Pressed Orange Oil, Brazilian EmCon Orange... 

Dugo G. et al., September/October 1992, High resolution gas chromatography for detection of adulterations of citrus cold-pressed essential oils, Perf. Flavor., 17, 57-74. 

Ohta, Y., and Y. Hirose Constituents of Cold-Pressed Peel Oil of Citrus natsudaidai Hayata. Agric. Biol. Chem. 30, 1196 (1966). 

Bicycloelemene (227) has been isolated from Conocephalum conicum 313) and detected in both Jungermanniales and the Metzgeriales species 28). The enantiomer of (227) has been isolated from pepermint oil 339) and cold-pressed peel oil of Citrus junos 274, 302, 317). 

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