Orange peel is two ingredients held together. The colored outer epidermis contains glands of aromatic oil, while the white, spongy albedo beneath is rich in pectin and protective bitter phenolics.1
The oil glands are concentrated in the zest, where a light scrape releases a bright aroma without much of the white layer. The albedo contributes body and bitterness instead. Citrus peel is also a useful source of pectin, the plant cell-wall material that helps fruit gels form, so the rind can change a preserve’s texture as well as its flavor.1 The fruit is a hesperidium: a specialized berry with an outer rind, a segmented juicy interior, and oil-bearing peel rather than the thin skin of an apple or a grape.1
The bitter compounds are water-soluble but the fragrant oils are not. Repeated cold soaking or brief changes of hot water can therefore leach bitterness while retaining much of the oil; gentle cooking then softens the pectin-rich albedo before sugar is introduced for candying.1 That same separation helps explain why zest, whole peel, and blanched rind behave so differently in sugar, salt cures, vinegar, cheong, kosho, and shio koji. University of Maine’s marmalade guidance makes the practical distinction explicit: preserving the colored rind while trimming away excess pith gives a brighter, less harsh result, while the remaining peel still supplies the pectin that helps the preserve set.2
Oranges and other citrus are subtropical trees rather than Northeast field crops, so orange peel enters a regional pantry as a preserved or traded ingredient rather than a locally grown one. That does not make it incidental. In a Northeast kitchen, peel is often the part of an imported citrus fruit that gives a locally made preserve, syrup, or ferment its most recognizable top note, even when the fruit itself is not a regional crop. The colored flavedo carries the volatile perfume; the pale albedo carries much of the structural work.