Citrus limetta, alternatively considered to be a cultivar of Citrus limon, C. limon 'Limetta', is a species of citrus, commonly known as mousambi, musambi, sweet lime, sweet lemon, and sweet limetta, it is a member of the sweet lemons. It is a cross between the citron (Citrus medica) and a bitter orange (Citrus × aurantium).
It is a different fruit from the Palestinian sweet lime and from familiar sour limes such as the Key lime and the Persian lime. However, genomic analysis revealed it to be highly similar to the Rhobs el Arsa, and the two likely shared a common origin.
C. limetta is a small tree up to 8 m (26 ft) in height, with irregular branches and relatively smooth, brownish-grey bark. It has numerous thorns, 1.5-7.5 cm (0.59-2.95 in) long. The petioles are narrowly but distinctly winged, and are 8-29 mm (0.31-1.14 in) long. Leaves are compound, with acuminate leaflets 5-17 cm (2.0-6.7 in) long and 2.8-8 cm (1.1-3.1 in) wide. Flowers are white, 2-3 cm (0.79-1.18 in) wide. Fruits are oval and green, ripening to yellow, with greenish pulp. The pith is white and about 5 mm (0.20 in) thick. Despite the name sweet lime, the fruit is more similar to a greenish orange in appearance.
As the name sweet lime suggests, the flavour is sweet and mild, but retains the essence of lime. The lime's taste changes rapidly in contact with air, and will turn bitter in few minutes, but if juiced and drunk rapidly the taste is sweet. The flavour is a bit flatter than most citrus due to its lack of acidity. It can be compared to limeade and pomelo.
Sweet lime is almost exclusively served as juice, and is the most common available citrus juice in the Indian subcontinent. The juice is commonly sold at mobile road stalls, where it is freshly pressed, sometimes served with a salty chat masala or kala namak, unless the vendor is told not to add it.
Like most citrus, sweet limes will not ripen off the tree, and must be picked when fully ripe. This is indicated by its tennis ball size and lustrous greenish yellow sheen. Gently scratch the surface of a sweet lime: If its oils give way in the fingernails, it is ripe. The juiciest fruits feel heavy for their size.
Underripe fruit feels light for its size, and is hard with tart flesh. Overripe fruit is dull and shrunken, with dry, spongy skin. Avoid fruit with brownish-yellow discoloration.
Sweet limes keep fresh for up to two weeks at room temperature, and four to eight weeks refrigerated. Frozen juice will keep for up to six months. It is possible to freeze slices of the fruit, though the limonin content may cause the pulp to taste bitter over time. This can be avoided by submerging the slices in sweet syrup within an airtight glass jar.