Citrus albedo

Nicol, K. J. Chandler, B. V. The extraction of the enzyme degrading the limonin precursor in citrus albedo. J. Sci. 

To remove the essential oil from the peel of citrus fruits, the oil glands, which are located in the flavedo (the outer coloured portion of the peel), are ruptured by mechanical systems. The oil is washed away with a spray of water to produce an oil-in-water emulsion with small peel particles. To prevent absorption of the essential oil by the spongy albedo (the iimer white portion of the peel), this emulsion is passed through a screening device (finisher) of 0.5 to 0.7 mm in diameter, which removes the coarsest particles of the fruit peels [12]. 

In fruit penetration studies 8 pounds of fruit were first thoroughly scrubbed with warm 10% trisodium phosphate solution and then rinsed thoroughly with distilled water. Citrus fruits, if depth of penetration into the peel was of interest, were peeled in longitudinal sections with a buttonhook peeler and the albedo or white portion was separated from the flavedo or colored portion. The separated peel was placed in pie tins lined with waxed paper and dried in a forced draft oven at 65° C. for 16 hours. The dried peel was then crushed and steeped for 48 hours in a measured volume of benzene sufficient to cover the sample. If, on the other hand, only the total amount of DDT in the peel was of interest, the fruit was halved and juiced on a power juicer. The pulp was removed, the peel sliced, and the sample dried and treated as before. Thin-skinned fruits, such as apples, pears, and avocados, were peeled with a vegetable peeler, cores or seeds were removed, and the pulp was sliced in thin slices. Pulp and peel were then dried and treated in the same way as the citrus peel. The steeping completed, the samples were filtered through Sharkskin filter paper and the volume of benzene recovered was noted. 

Citrus Fruit Types. The method previously described 11) consisted essentially of scrubbing the fruits with a warm 10% trisodium phosphate solution, rinsing with distilled water, halving each fruit, and reaming the juice and pulp from each half with a power juicer. Pieces of pulp adhering to the insides of the individual hemispheres of peel were carefully scraped free and combined with the remainder of the pulp and juice. Independent analyses were then completed on the discrete peel and pulp-juice samples. Whenever desirable the flavedo and albedo components of the peel were separated with peeling tools, and each was pooled and analyzed. 

Botanically speaking, citrus is a hesperidium, a berry with a leathery aromatic rind and a fleshy interior divided into sections. As shown by the cross section shown in Fig. 6.1, the exo carp or peel consists of an outer layer called the flavedo which contains oil glands and pigments and a white spongy inner layer called the albedo. The fleshy interior or endocarp of the fruit consists of wedge-shaped sections (segments) filled with multiple fluid-filled sacs or vesicles. These juice sacs constitute the edible portion of a citrus fruit. The cytoplasm contents provide the primary source of the citrus juice. The juice consists primarily of water, sugars, pectins, lipids, terpenes, amino acids, phenolics, carotenoids and minerals. 

Comminutes. The process of comminution refers only to citrus products, where the oils that reside in the flavedo (coloured peel) have intense flavour characteristics. At its simplest, comminution involves taking a complete orange (or other citrus fruit) and making a pulp from it. This pulp will have a much more intense flavour than juice alone but because of the presence of much peel and albedo (pith) it would be unacceptable in taste to most consumers. Thus, the process of comminute production, developed in the immediate postwar years, is typically as set out in Figure 6.1. 

Flavonoids are not evenly distributed within citrus fruit. Flavanone glycosides are concentrated primarily in the albedo,... 

Citrus fruits, especially certain of their component parts, constitute one of the richest sources of pectin. On a dry weight basis, as much as 30% of orange fruit albedo may be pectin (8). The rag, comprising the fruit core and segment membranes after juice extraction, is also a rich source. Since pectin is a cell wall component, it follows that comparatively little would be present in juice expressed from fruit. For example, concentrations ranging from 0.01 to 0.13% in orange juice have been reported (15). Much of this would be present as cell wall fragments and particulate material in juice pulp and cloud. 

Hasegawa, S. Maier, V. P. Bennett, R. D. Detection of limonoate dehydrogenase activity in albedo tissues of Citrus sinensis. Phytochem., 197A, 13, 103-105. 

The protein in citrus is generally associated with the solid portions of the fruit, i.e., the seeds, flavedo, albedo, chroma-tophores, and pulp. Some of these components find their way into the juice along with the available free amino acids during extraction and processing and storage. Studies conducted in our laboratories (42,43,44) and by others (45) have shown that reductions in the pulp content of juice slow the rate of browning. 

Maraulja and Dougherty (131) reported chloramine-T values for Florida Hamlin, Pineapple and Valencia were slightly higher for hard squeeze juices than for soft squeeze juices. Chloramine values were considerably higher for the albedo and flavedo components than for juice and were suggested for detecting adulteration with water extracts of peel and rag (75,132). Chloramine values are often included with other analytical parameters for citrus juice authentication (133,134). 

Fluid loss from dry-pack segments was found to be correlated with loss of membrane strength. In stored, dry-pack unpasteurized grapefruit segments, naringin crystals formed in albedo cells still adhering to section membranes after treatment. Crystal formation was minimized by water sprays or lye solution dips. This process provides a new approach for commercial sectioning of citrus. 

Cltnis oHs. Essential oil obtained from the peel of citrus fruits (bergamot, grapefruit, lime, mandarin, orange, lemon). Since the oil is stored in small bubbles in the outer peel (albedo) it can be isolated by mechanical processes. C. are thus known as pressed or cold-pressed oils. 

Zhang JK, Zhu XY, Luo FL, Sun CD, Huang JZ, Li X, Chen KS (2012) Separation and purification of neohesperidin from the albedo of Citrus reticulata cv. Suavissima by combination of macroporous resin and high-speed counter-current chromatography. J Sep Sci 35 128-136... 

Aleson-Carbonell et al., (2005) assessed that albedo of citrus fruits could be an interesting functional ingredient to improve the cooking properties of beef patties, because better fat and water retention reduces cooking losses in meats. Furthermore, if an increase in dietary fiber is normally recommended in some specific diets, the increased fiber content constitutes an additional nutritional benefit for the consumer. The use of citrus fiber could be attractive to some consumers as a positive alternative to conventional fillers in meat-based products. The effects of citrus fruit (lemon, orange, mandarin, etc.) extracts and their byproducts (albedo, rind and fiber powder, etc.) have been reported on Upid oxidation of meat products, whether fresh (Aleson-Carbonell et al., 2005), cooked (Viuda-Martos et al., 2009) or dry cured (Femandez-Lopez et al., 2008). 

In industrial practice, pectins are mostly extracted from citrus fruit peels (their albedo), which contain about 20 0% of pectin. Another source of pectin is apple pomace, containing about 10-20% pectin. The isolation of pectin is based on extraction from an acidified aqueous slurry (pH 1.5 3) at temperatures of 60-100 °C. The extracts are then concentrated by evaporation or dried. Commercial pectin products are obtained by precipitation using metal ions that form insoluble salts with pectin (e.g. Al +), or by precipitation of pectin solutions with alcohols (ethanol or propan-2-ol). 

The white, fibrous material which lies between the segments and the peel of citrus fruits. It constitutes from 20 to 60% of the whole fruit, and is used in the production of pectin. The albedo is rich in fiber and bioflavonoids. 

Another name for the albedo of citrus fruits, which is the white fibrous matter that lies between the fruit segments and the outer pigmented portion of the peel (flavedo). Citrus pith is rich in (1) bioflavonoids, and (2) pectin, a gelling agent and an ingredient in diarrhea remedies. 

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