Mursik is a traditionally fermented milk variant of the Kalenjin people of Kenya. It can be made from cow or goat milk and is fermented in a specially made calabash gourd locally known as Sotet.
It is prepared primarily from cows' milk fermented. It is made in specially seasoned milk gourds that are pre-treated with the smoke and charcoal of certain species of trees prior to each use.
Fresh/raw milk (or, more commonly in modern times, milk that has been first boiled then cooled to ambient temperature) is poured into the specially prepared gourd. The gourd is then capped and placed in a cool dry place to undergo spontaneous fermentation for at least three to five days, through the action of lactic acid bacteria, yeast and mould species.
Traditionally in some communities, but very rarely in modern times, fresh blood tapped from a cow may have been added to fresh milk before fermentation, or to already fermented milk.
Lactobacillus Plantarum was found to be the most dominant of the lactic acid bacteria involved in the production of mursik. Other lactic acid bacteria isolated from mursik are Leuconostoc mesenteroides and Enterococcus faeciu.
Smoke and charcoal from specific trees has long been used in the traditional production of fermented milk products in Kenya. Among the common tree species used by farmers for milk treatment in the production of mursik are Senna didymobotrya, Lippia kituiensis, Prunus Africana and Olea europaea ssp. africana.
A gourd is smeared inside with special charcoal called "osek"; from this, grey lines can be seen when pouring the thick, sour milk. In preparing the gourd, the Kalenjin women, for instance, make a brush (sosiot) from a branch of cycad tree used to clean the inside. Brushes made from this tree are hardy and may last for up to two years before replacement.
Charcoal "osek", formed from the smouldering embers of branches from the Ite or Itet tree (peanut butter cassia, scientifically known as Senna didymobotrya ), is used as a milk preservative.
Women use the embers to coat the inside of the cleaned gourd. The charcoal has various effects. It lines the inside of the gourd, reducing its porosity rendering it airtight. The smoke from the embers also has a preservative effect which prevents undesired bacterial multiplication that causes spoilage, while allowing natural souring.
The charcoal smoke imparts a special flavour to the milk and a bluish colour which is of high aesthetic value to the consumer. Having prepared the gourd, women pasteurize the milk by boiling. The pasteurised milk is left to cool before pouring into the gourd. Finally, the gourd is corked to render it airtight, making it possible for the milk to be preserved for up to a month.