Citrus oils determination

Mondello et al. (2, 20-23) have used a multidimensional gas chromatographic system based on the use of mechanical valves which were stable at high temperatures developed in their laboratory for the determination of the enantiomeric distribution of monoterpene hydrocarbons (/3-pinene, sabinene and limonene) and monoterpene alcohols (linalol, terpinen-4-ol and a-terpineol) of citrus oils (lemon, mandarin, lime and bergamot). Linalyl acetate was also studied in bergamot oil. The system consisted of two Shimadzu Model 17 gas chromatographs, a six-port two-position valve and a hot transfer line. The system made it possible to carry out fully... 

Citrus oils contain up to 95% monoterpene hydrocarbons (usually limonene, but others as well, e.g., lemon oil also contains a-terpinene and /3-pinene). The important aroma-determining components of citrus oils are functionalized terpenes and aliphatic compounds (predominantly carbonyl compounds and esters), present only in relatively low concentrations [358]. Thus, several methods are employed to concentrate citrus oils on an industrial scale. The monoterpene hydrocarbon... 

Interfaciai Tension Procedure. IFT measurements were made by the Wilhelmy plate method. The apparatus was the same as that described previously (2). A standard protocol was followed for all IFT determinations. The desired interface was formed at a specified temperature by partially filling a thermostatted sample holder with the desired aqueous phase. This phase, distilled water (mono triple) or a supernatant aqueous phase isolated from a complex coacervate system, completely covered the Wilhelmy plate (roughened platinum). The desired citrus oil was carefully layered onto the aqueous phase. It had been preheated (or cooled) to the same temperature as the aqueous phase. Once the citrus oil/aqueous phase interface was formed, the Wilhelmy plate was drawn completely through the interface and into the oil phase where it was zeroed. 

Support Protocol 1 Determination of Moisture Content Basic Protocol 8 Quantification of Total Aldehydes in Citrus Oils by Gl.5.10... 

The quality of citrus oils is based on the purity of the sample as determined by a gas chromatogram (GC) profile. A small sample is injected onto a column, which separates the individual components. Separation is based on the physical interaction between the column and the sample as indicated by retention times. Figure Gl.5.1 illustrates the GC setup. 

Gas chromatography provides a rapid analysis of citrus oil quality. This technique can be further enhanced to determine quantitative levels of individual compounds. Compounds can be measured based on the FID response. A standard curve with known concentrations is used to extrapolate an unknown concentration. 

JA Albanese, CJ Mussinan. HPLC determination of psoralens in citrus oils. Pittsburgh Conference, Atlanta, Georgia, 1993, p 448. 

Use of GLC to determine qualitative and quantitative composition of volatile compounds in citrus oils has become common. However, there are many discrepancies in the literature concerning the quantitative composition of citrus oils. Analyses of volatile aldehydes are of major importance, because composition and quantity of these compounds influence the quality and value of citrus oils. Compositional differences between... 

Ultraviolet Absorbance Determine as directed under Ultraviolet Absorbance of Citrus Oils, Appendix VI, using about 50 mg of sample, accurately weighed. The absorbance maximum occurs at 315 3 nm. 

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. 

Classification of the citrus oils was possible by using Soft Independent Modeling of Class Analogy (SIMCA). This type of algorithm is designed to compare new samples against previously-analyzed sets. Another ability if SIMCA is the determination if a sample does not belong to any predefined class. 

Faulharber et al (5,6) and other researchers (7-9) have described how the determination of the isotope values of constituents is of increasing importance, especially in view of the demand for authenticity control and origin determination of essential oils and foods. To determine isotope values, g chromatography-isotope ratio mass spectrometry (GC-IRMS) has been used, although not widely. The present authors (70) have studied the possibility of a more convenient and common means of analysis of isotope values, based on the isotope peak in the mass spectrum of a compound. The present study focuses on the development of a new analytical method for the differentiation of quality in commercial citrus oils of various origins. 

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. 

In this paper, work is presented showing capillary SFC analyses of a soybean oil, a hops extract, a celery seed oleoresin, and an essential citrus oil. In addition, results showing the determination of pesticide residues in a parsley sample by capillary SFC are presented. 

For the ethanol-water system, Ikawa et al. [11] determined HETP to 0.4 to 0.5 m at high liquid loadings. Sato et al. [12] measured HETP in citrus oil systems to vary between 0.5 and 3.8 m, depending on the ratio of solvent to feed. Analysis with respect to HETP is carried out very differently in literature. Therefore, comparison is not easy. Since the ratio of gas and liquid flow in the column VtL) is determining the separation in a countercurrent separation process, loading values for the gaseous and the liquid phase should be used for characterising the concentration, as is done in other separation processes. 

UV spectroscopy has only little sign cance for the direct analysis of essential oils due to the inability to provide uniform information on individual oil components. However, for testing the presence of furanocoumarins in various citrus oils, which can cause photodermatosis when applied externally, UV spectroscopy is the method of choice. The presence of those components can be easily determined due to their characteristic UV absorption. In the European pharmacopoeia, for example, quality assessment of lemon oil, which has to be produced by cold pressing, is therefore performed by UV spectroscopy in order to exclude cheaper distilled oils. 

Surface oil is typically determined only on encapsulated essential oil products. This is because some of the essential oils (e.g., citrus oils) are extremely labile to oxidative deterioration. This analysis is not performed on a routine basis but only occasionally to monitor the spray drying process. 

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