The longan fruit is normally eaten fresh like that of lychee. It is particularly popular among Asians, particularly the Chinese. There are claims among some people in China and Thailand that the taste of longan equals or is superior to that of lychee. Fresh longan fruit has a short shelf-life. To extend the uses of the fruit the longan can be frozen, canned or dried. Longan fruit can be frozen in its skin in airtight containers. Upon thawing, the fruit can be used in similar manner as freshly picked fruit without any loss of quality. The fruit can be canned in its own juice with little or no added sugar. This is possible because the longan flesh contains a high level of soluble solids. For canning, cultivars with large fruit and small seed are preferably used. Canned longan retain their individual flavour better than lychee or 'rambutan'. Drying the fruit, either intact or after removal of the pericarp, is a practical way of preserving the longan fruit. The dried aril is black, leathery and smoky in flavour and is used mainly to prepare a refreshing drink. This drink is very popular among the Chinese. A liqueur is made by macerating the longan flesh in alcohol. Dried longan flesh is also an ingredient in herbal medicine used for stomach ache, insomnia and as an antidote for poison.
The seed is used as a shampoo, like soapberries (Sapindus saponaria L.), due to its saponin content. Dried leaves, which contain quercetin and quercitrin, and flowers of longan are also sold as ingredients in Chinese herbal medicine.
Figure 1. The commercial longan (Dimocarpus longan ssp. longan var. longan).
Figure 2. Relatives of the commercial longan - Dimocarpus longan ssp. malesianus var. malesianus (from left to right: 'kakus', 'isau' and 'sau').