Parmotrema cetratum

Overview

Parmotrema cetratum is a lichen, a fungus living in partnership with an alga, that grows on trees. In Nepal it is one of three lichens eaten by the Limbu and Rai communities, and it is known there as yangben. The catalogue calls it an edible Himalayan lichen.

Yangben is a signature ingredient of Limbu cooking. It is cooked mainly with pork and is part of festival and gift-giving customs.

Identity

The catalogue warns not to confuse this species with other Parmotrema sold as spices. The species name in the record is a research name, and the catalogue does not reconcile it with a current accepted name.

The three lichens named in the Kathmandu Post feature are Everniastrum cirrhatum, Everniastrum nepalense and Parmotrema cetratum. A Nepal Himalaya study of lichenophilic communities records Everniastrum nepalense and P. cetratum as eaten by the Limbu and Rai peoples.

Ecology and habitat

The catalogue describes it as a tree-dwelling lichenised fungus, and records its supply as wild. The Kathmandu Post feature reports that the lichens grow on old chestnut, rhododendron and alder trees.

The feature reports that the traditional lichen is becoming less available, and links this to overharvesting and to road dust. These are reported views, not measurements.

Preparation

The Kathmandu Post feature describes the traditional method. The lichen is boiled for a few hours with firewood ash, which turns it from light greenish-white to dark brown. The article states that the alkaline ash removes toxicity and reduces bitterness. It is then washed in cold water until the water runs clear, sun-dried and stored.

After soaking in hot water it is mixed with blood and spices and cooked with pork. The main dishes named are yangben-faksa, a pork dish with fatty skin, pig's blood, lichen and spices, and sargemba, a blood sausage with minced meat or innards.

Cultural role

The feature describes yangben as the Limbu community's signature speciality. It has traditionally been given to relatives as a gift, and is prepared during several Limbu festivals, including Dashain and Tihar. The black pig is revered by Limbu and Kirat people and offered to ancestral deities.

Neighbouring Rai and other communities have also adopted the dish, according to the feature.

Safety and identification

The Kathmandu Post article says the ash boil removes toxicity. That is a traditional practice reported in a news feature. It is not a tested process, and this record does not give the ash quantity, boiling time or alkalinity that the method needs.

A food technologist quoted in the same feature says the lichen's high fibre content reduces the fat the body absorbs from pork. The article cites no study for this view, so it is recorded as an opinion only.

Identification of lichens and the separation of food species from spice species need a specialist. The catalogue's caution applies: do not conflate with other Parmotrema sold as spices.