Kumquat marmalade is a sweet, exotic alternative to ordinary orange marmalade. It is generally slightly tarter than its orange cousin, but has the same crystal orange color and thick texture. Although kumquat marmalade is relatively easy to make, there are a few tips for making a delicious batch almost every time. One should choose perfectly ripe kumquats, taste the kumquats to judge sweetness, and add flavor by using orange juice instead of water.
Picking ripe kumquats is one of the most important steps to making kumquat marmalade. About the size of a man’s thumb, these sweet little fruits should be bright orange in color and give slightly when squeezed. They should also smell fresh and clean, without a trace of mustiness or sharpness. A musty odor may indicate overripe fruit, while sharpness indicates a green fruit. Green kumquats often taste sour, while overripe fruits can give kumquat marmalade a cloying, moldy flavor.
Tasting the fruit is another integral part of making kumquat marmalade. Eating one or two kumquats usually helps a cook judge how sweet they are, which allows him to adjust the amount of sugar needed. A very sweet batch of kumquats may not need any sugar at all, while a relatively tart batch may require twice the usual amount.
After tasting, the cook may slice up the kumquats into very small pieces. Cooks should cut seeds from kumquats, but the skin is usually just as sweet and edible as the flesh. The next step is to pour the kumquat slices into a large enamel or stainless steel pot with liquid to start them simmering. Aluminum pots should typically be avoided because they can give kumquat marmalade a metallic flavor.
Mixing about 3 parts liquid with about 4 parts of kumquat slices usually works well. Some cooks use water, but substituting orange juice generally gives kumquat marmalade a lot of extra flavor. One may use freshly-squeezed or store-bought orange juice, leaving in or straining out the pulp as desired. The only requirement is that the orange juice be in proper proportion to the kumquats.
Once in the pot, kumquat marmalade typically needs to simmer for one to three hours, or until the peels of the kumquats are easy to cut with the edge of a metal spoon. At this point, the mixture must cool for up to 10 hours, ad typically overnight, to allow it to thicken slightly. After the mixture is very cool, the cook may bring it back to a boil and add sugar, if any is necessary. The marmalade should thicken to a jam-like consistency after 30 to 45 minutes of subsequent heating. The cook may then pour the finished marmalade into clean jars while the mixture is still warm.