Orange peel oils

Portugaldl, Portugallool, n. Portugal (or por-tugallo) oil, orange-peel oil. 

In the non-recycling system, the pectic substance content of the different samples were very stable (Figure 2a). At the end of the assay the oil-in-water emulsion from the finisher and both aqueous discharges had very similar values of around 0.2 g AGA/L, similar to that reported by Parish e( al. [5] for the aqueous discharge fi"om an orange peel oil recovery system. However, the oil-rich emulsion had higher values (around 4.0 g AGA/L). 

Orange peel oil is the major oil produced worldwide and is used extensively in the food industry, primarily as a flavouring in beverages and sweets. It possesses a light, sweet, fresh top note with fruity and aldehydic character. Many household and personal-care products employ orange oil owing to its pleasing... 

Sweet orange peel oil composition has been reviewed in [1,4]. 

Mandarin peel oil volatiles contain many of the same volatiles as orange peel oil however, there are a few differences such as elevated levels of dimethyl an-thranilate and thymol. It has been reported [54] that the characteristic mandarin peel oil aroma was due to a combination of dimethyl anthranilate, thymol, a-terpinene and /1-pinene. 

The main renewable resource for L-carvone is spearmint oil (Mentha spicata), which contains up to 75% of this flavour chemical. There also exists a synthetic process for the manufacturing of L-carvone, which is based on (-t)-limonene, which is available as a by-product of the citrus juice industry as a major component of orange peel oil (Scheme 13.4). The synthesis was developed in the nineteenth century and starts with the reaction of (-t)-limonene and nitrosyl chloride, which ensures the asymmetry of the ring. Treatment with base of the nitrosyl chloride adduct results in elimination of hydrogen chloride and rearrangement of the nitrosyl function to an oxime. Acid treatment of the oxime finally results in l-carvone. 

Nootkatone is an important constituent from grapefruit flavour. It is synthesised by oxidation of valencene, which is obtained and isolated from orange peel oil where it occurs at a maximum level of 0.4% [9]. 

Dryer Temperature Study. An orange peel oil/gum arabic emulsion was prepared and spray dried as previously described. Six runs were made varying both the inlet and exit air temperatures (Table I). 

Effect of Water Activity. A preliminary study was done to determine the a at which encapsulated orange peel oil was the most stable to oxidation. Figure 1 summarizes the results of this study. The formation of the limonene oxidation product, limonene oxide, was the slowest for the powder adjusted over Mg(NO3)2 (a 0.536). While the levels of oxidation product do not follow in exact order of a, it is evident that better storage stability correlates with a higher a of the powder. This relationship was not anticipated. Literature on lipid oxidation (2, 2) indicates that there is an optimum a for product... 

Once we had determined the optimum practical a for the storage of encapsulated orange peel oil, we initiated a study on the influence of spray dryer inlet and exit air temperature on product shelf-life. 

Figure 1. Effect of water activity on shelf life of encapsulated orange peel oil.

Figure 2. Influence of inlet and exit air temperatures on the moisture content of spray dried orange peel oil.

Storage Stability. The formation of limonene oxide at 37 C was measured as a function of time to determine shelf-life of the encapsulated orange peel oil samples. Figure 6 shows the shelf-life results. A value of 2mg limonene oxide/g limonene was used as the end of shelf-life for oxidized encapsulated oil samples ( 3) The sample dried at 160 C and 105 C inlet and exit air temperatures respectively and the smallest temperature differential (55 C). This sample formed limonene oxide much faster than the other five samples. By 23 days, this powder had reached a value of 2mg limonene oxide/g limonene. The sample dried at 280 C and 105 C inlet and exit temperatures respectively did not reach 2 mg limonene oxide/g limonene until after 34 days of storage at 37 C. This sample also had the largest inlet and exit air temperature differential (175 C). The remaining four samples had reached 2mg limonene oxide/g limonene after about 30 days of storage at 37 C. 

The extrusion process of Swisher (1 ) has formed the basis of the current commercial processes which exist today. Swisher (1) added an essential oil (e.g., orange peel oil), which contained antioxidant and a dispersing agent, to an aqueous melt of corn... 

Swisher (1 ) conducted an accelerated spoilage test on the product (encapsulated orange peel oil) he obtained via this process and estimated shelf-life at about 1 year. 

In brief, the extrusion process involved emulsification of orange peel oil into a melt of the ingredients described above. The molten products were then extruded under pressure through a die template into a chilled isopropyl alcohol bath. Subsequently, the products were broken into small, rod-shaped particles and dried to remove the alcohol. 

Table II. Shelf Life of Encapsulated Orange Peel Oil...

The stability of orange peel oil depends on the selection of the encapsulation process and the encapsulating agent. The results of this study indicated that the differences in shelf life were greatly accentuated at higher temperatures. The shelf life of the spray dried products ranged from 5-35 days compared to the extrusion and beta-cyclodextrin products which were still acceptable after 180 days at 50 C. 

Overall, extrusion encapsulation provided superior protection of orange peel oil as measured by epoxide formation. The molecular inclusion of orange oil via beta-cyclodextrin also provided very good protection although the limonene-1,2-epoxide concentrations were consistently higher than for the extrusion products. 

Brunner et al [1, 2] investigated separations of fatty acids according to chain length, using methyl esters of different carbon chain length from C14 to Cl8, separation of tocopherols from a by-product of the edible oil production and separation of fish oil esters [3], Stahl et al [4] proposed the supercritical fractionation of orange peel oil and Reverchon et al [5,6] of an orange flower concrete. Different authors treated citrus peel oil [7,8] and citrus oil [9-12]. 

Polymethoxylated flavones are also characteristic of orange peel oils, and PMF determination has been used to ascertain the geographical origin of industrial peel oils (110). A normal-phase HPLC method for the determination of flavones in orange and mandarin oils was developed by Gaydou and co-workers (111). Using the normal-phase mode with a Licrosorb Si60... 

For the confirmation of PMFs in Valencia orange peel oil and juice, an HPLC method coupled with a thermospray mass spectrometry (HPLC-TSP-MS) detection system was utilized (112). A C 8 column (/zBondapak, 300 X 6-mm ID) was used with a mobile phase of H20-ACN (60 40, v/v) at a flow rate of 1.0 ml/min. Extract (20 fi1) was injected into the HPLC-TSP-MS system, and positive-ion spectra from m/z 100 to 700 were recorded at 1360 ms. Mass spectro-metric identification was done using positive chemical ionization (ICP). This technique allowed confirmation of the presence of eight flavones in the peel oils and seven flavones in the juice. 

EM Gaydou, T Berahia, JC Wallet, JP Bianchini. Gas chromatography of some polymethoxylated flavones and their determination in orange peel oils. J Chromatogr 549 440-445, 1991. 

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