Gamma and gamancho

What it is

Gamma and gamancho are names for a starter used in the fermentation of enset, the false banana of the Ethiopian highlands. A source consulted for this page describes the corm of the enset plant as the fermenting agent, a locally prepared starter called gamma or gamancho, with no standard composition. Each community makes and keeps its own, so the names and recipes vary by region.

The starter is not a single purchased culture. It is material taken from enset itself and kept for the next batch, so its composition depends on the plant, the season, the handling and the people who keep it.

Different names in different places

A survey of selected districts in southern Ethiopia reports Gamma in Dawro and Wolayita and Gamancho in Sidama. It also records other names, including Gamama, Gegema, Gemama and Gemma/File, in other surveyed zones. Materials and practices differ between these communities, so the names should not be treated as synonyms or as one standardized starter. The survey documents its surveyed communities; it does not establish an origin or the full distribution of each practice.

A separate Dawro study uses the name gammicho and mentions locally named herbs. The sources reviewed here do not show that gammicho is a general synonym for Gamma or Gamancho. Local spelling, pronunciation and boundaries need review with knowledge holders.

The food it starts

Kocho is the fermented food made from enset. It is described as a bread-like food and a staple in Ethiopian cuisine, made from the scraped leaf-sheath fibre and the pulverised corm, or from the pith of the pseudo-stem. It is eaten with kitfo, gomen and ayibe, and it is used to scoop up stews.

Kocho can be stored underground for three to twelve months, a reserve for lean periods. Traditional fermentation takes months, and the range given runs from several weeks to two years, depending on the account.

The plant, the starter, the fermenting mash and the finished food are four separate subjects. A 2024 Dawro study describes Gamma as material carried over from an earlier fermentation, but that account belongs to its sampled local process and should not be generalized to every enset tradition.

What the starter contains

Fermenting enset is dominated by lactic acid bacteria, and the genera most often named are Leuconostoc, Lactobacillus and Weissella. A study of gamma reported that lactic acid bacterial counts rose until about day 30 of fermentation, as the pH fell and the bacteria tolerated the acid. The starter is therefore part of a lactic process that narrows the community as acid builds.

Isolates from Arba Minch University were characterised as Lactobacillus and Streptococcus, and the authors concluded they could be used to prepare a starter culture that would shorten fermentation. Their starter-fermented kocho scored higher than traditionally fermented kocho on nutritional content, colour, odour, texture and acceptability. A response-surface study reported the preferred sensory quality from 2 per cent Lactobacillus plantarum at six days.

Spontaneous communities and selected-strain experiments

Research on kocho separates two things. Studies of ordinary fermentations describe communities that change over time and differ between samples: in the Gamo highlands, Leuconostoc mesenteroides is described early in fermentation and other taxa in later samples, and another study cultured yeasts, lactic acid bacteria and aerobic bacteria from fresh, middle-aged and long-fermented kocho. These findings describe the sampled material. They do not identify one kocho community or show that an isolated organism should be added to food.

Separately, two research tracks test selected lactic acid bacteria as starter candidates. One characterised bacteria isolated from kocho and tried selected Lactobacillus strains with enset pulp at laboratory scale; another screened isolates from fermenting enset and from traditional starter material, then evaluated three chosen strains under field-study conditions. The results apply to those strains and batches. They do not show that households use the strains, or that they suit household use. A 2024 experiment on fermentation time and temperature, like the pit, basket and jar comparison, is tied to its own vessels and measurements and sets no household limits.

What the studies do and do not show

Microbial results are tied to particular samples. The 2019 survey reports Clostridium spores in its sampled traditional starters. The 2024 Dawro study reports no detected Clostridium in its Gamma sample. Different samples and methods may account for the difference, and neither result establishes the safety of all local starters or processes.

A separate study compares fermentation systems, including pits, bamboo baskets and a jar, but its abstract does not establish that one is a household substitute for a named Gamma or Gamancho practice. A Wikipedia article on kocho names yeast as the starter and does not mention gamma; the microbiological studies above describe lactic acid bacteria as the dominant organisms, so the sources differ on the leading organism and this page does not choose between them.

Variation and the limits of the evidence

Studies report that there is no standardised starter in the highlands, which contributes to variable kocho quality and prices. Propagation and care vary regionally, and no source reviewed supplies one complete, locally validated household method, starter-storage guidance or a general safety endpoint.

Most starter studies are small theses or single trials. One Addis Ababa thesis reported good quality in 24 to 28 days with an inoculated starter, which it set against about six months for natural fermentation. No published comparison of gamma itself with defined lactic starters was found, so none is claimed here.