Ragi tapé

What ragi tapé is

Ragi tapé (ragi tapai in Malay) is a dried starter cake used for fermented starchy foods, above all the sweet fermented glutinous rice called tape ketan and fermented cassava. It is a mixed culture, not one organism, and it is separate from ragi tempe, the starter for tempeh. Research on the cakes finds starch-degrading moulds such as Amylomyces and Rhizopus together with yeasts such as Saccharomycopsis and other yeasts and bacteria.

Because the cakes are a community, they differ from market to market. One study collected cakes from six markets across West, Central and East Java and examined the Amylomyces rouxii in them. Other work examines specific Indonesian or Malaysian commercial samples. None of this establishes one composition for everything sold as ragi.

What it does

The moulds break starch down to sugars and the yeasts turn those sugars to alcohol, which is why the same cake can make a sweet, lightly alcoholic rice or cassava and, with further work, related drinks. Baker's yeast alone cannot take its place, because it lacks the starch-degrading part.

In a potato-pulp experiment with Indonesian ragi tapé, researchers detected several fungi and measured lactic acid and ethanol in that batch. They also noted that the marker used could not cleanly tell two mould names apart. These results describe that sample and experiment and are not a universal ingredient list.

Rice, cassava and Sabah

Indonesian research documents ragi tape in connection with tape ketan, fermented glutinous rice. A West Java review describes peuyeum as a fermented cassava food associated with Bandung and lists fried peuyeum, colenak and cakes among its uses; those are uses of the finished cassava food and not of the starter.

In Sabah, Malaysia, a traditional rice-wine starter called sasad has been examined for its microbiota. It is a useful regional comparison, but the sources do not establish that sasad and Indonesian ragi tapai are the same product.

Buying and keeping it

The catalogue advice for purchased cakes is to keep them dry and to use them in the food process they are meant for. Renewing or propagating a ragi cake is a separate activity from making tapai, and no validated household method for making the starter, no general dry-starter storage period and no safety limit for a particular cassava or rice batch has been established in the sources. For cassava especially, process and safety need authoritative evidence for the exact product.

History and what is unknown

The sources give no earliest origin, no seasonal calendar and no single microbial formula for ragi tapé. Local naming, history and use would need Indonesian-language historical and producer sources, which this page does not have.