Citrus peel oils composition

The economic importance of the various citrus oils has resulted in intensive research directed toward processing methods, compositional analyses, quality, and utilization. Early work described recovery methods and some characteristics related to quality of citrus peel oils in the United States (UO, 11). More recently, citrus peel oil yield and quality has been related to processing methods (12) and cultural practices (13). 

Citrus peel oils of very complex composition are contained in oval, balloon-shaped oil sacs, or vesicles, located in the outer rind, or flavedo, of the fmit (3). The oil is usually extracted by mechanical separation or hydrodistUlation. The five main types of citrus from which peel oils are recovered are orange, grapefruit, tangerine, lemon, and lime (4). Mechanical separation, known as cold-pressing of peel oils, does not use heat in order to avoid loss of volatile components. Swisher and Swisher (1) described three general commercial methods that are widely used in citrus industry to extract crude oils from fruit peels ... 

Compositions of volatiles in different orange oils are shown in Tables 4 and 5. It is evident that most of the constituents belong to the terpene family and may be arranged into two groups, terpene hydrocarbons (terpenes and sesquiterpenes) and oxygenated terpene products (21). Aside from the volatile components, there are small amounts (2-15%) of nonvolatile residues in citrus peel oils that possess antioxidative property these include coumarins, psoralens, and polymethoxylated flavones (30-34). 

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). 

There is considerable interest in the chemical composition and properties of citrus oils and essences as well as the role they play in food and nonfood industries. Citrus peel oils and essences possess a pleasant aroma, with oxygenated compounds being the major constituents that account for their characteristic odor. Terpenes, the most abundant components in cold-pressed citms peel oil, are removed in concentrated oil production, usually by use of adsorbant and supercritical carbon dioxide, to increase the concentration of oxygenated compounds and to enhance the qualification of the oil. Meanwhile, citms seed oils are composed largely of triacylglycerols and are rich in oleic and linoleic acids. 

Dugo G, Mondello L., 2011, Composition of the Volatile Fraction of Citrus Peel Oils in Citrus Oils— Composition, Advanced Analytical Techniques, Contaminants, and Biological Activity, Taylor Francis Group, Boca Raton, FL, p. 147. 

Mondello et al. (54) have developed some applications of on-line HPLC-HRGC and HPLC-HRGC/MS in the analysis of citrus essential oils. In particular, they used LC-GC to determine the enantiomeric ratios of monoterpene alcohols in lemon, mandarin, bitter orange and sweet orange oils. LC-GC/MS was used to study the composition of the most common citrus peel, citrus leaf (petitgrain) and flower (neroli) oils. The oils were separated into two fractions, i.e. mono- and sesquiterpene... 

Production of Citrus Essence Oils. Distillative concentration of citrus juices yields essence oils, which separate from the aqueous phase in the receiver when the distillate condenses. The composition of essence oils is similar to that of peel oils, but the essence oils usually contain larger quantities of aliphatic ethyl esters (e.g., ethyl butyrate in orange essence oil). Thus, their aroma resembles that of a particular juice more than that of peel oils. 

Pineapple oil, peel-oil content and aldehyde composition, see also Citrus oils Pin milling, starch isolation, 673, 677 Pipetting technique, 754-755 PL. see Pectic lyase... 

On a commercial basis, lemon Petitgrain oil is produced from citrus leaves in Italy. In contrast to other Petitgrain oils, its composition resembles more to the peel oil of the corresponding fruits. The main constituents are limonene (app. 30%), P-pinene (10-20%) and citral (15-28%) [104, 109-114]. 

Giamperi, L., Fratemale, D., and Ricci, D., Essential oil composition and antioxidant activity of peels of Citrus sinensis blood and blond Citrus aurantium, Rivista Italiana EPPOS, 12, 21, 2002. 

Kita, Y., Y. Nakatani, A. Kobayashi, and T. Yamanishi Composition of Peel Oil from Citrus Unshiu. Agric. Biol. Chem. 33, 1559 (1969). 

The enantiomeric ratio of limonene was used to discriminate genuine mandarin and lemon oils fi om the reconstituted ones [28, 29]. The enantiomeric excess of (+)-limonene in the lemon peel has been found between 97.1 and 97.4% [30]. Mondello et al. found small differences in the enantiomeric composition of monoterpenes between two varieties of lime oils Citrus aurantifolia Swingle (Key lime) and Citrus latifolia Tanaka (Persian lime) [31]. The enantiomeric ratio of limonene was the... 

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