Tapai – tape ketan in Indonesia, tapai pulut in Malaysia – is steamed glutinous rice fermented with a dry starter called ragi until it turns soft, juicy, sweet, slightly sour and gently alcoholic. It takes about two to three days in a warm spot. Cassava tapai (tape singkong) is made the same way from cooked cassava.
How Tapai Works
Ragi tapai are small, dry balls of rice flour carrying molds, yeasts and bacteria. The mold’s enzymes turn the rice starch into sugar, which is why tapai becomes so sweet and syrupy; yeasts then turn some of that sugar into alcohol, and bacteria add a little acidity. In a classic study of tape ketan made with Indonesian ragi, the mold Amylomyces rouxii and the yeast Candida pelliculosa dominated, with a smaller role for Saccharomyces cerevisiae; bacteria such as Bacillus and Acetobacter also contributed, and the ragi was the main source of all of them (Ardhana and Fleet, 1989). Tapai made with only pure mold and yeast cultures wasn’t of typical quality – the mixed community matters.
Ragi varies: molds isolated from ragi across Java belonged to two groups, related to Amylomyces rouxii and Mucor indicus (Delva et al., 2022). At 30°C, researchers found tape ketan ready to eat after about 48 hours, with sugar, alcohol and lactic acid produced along the way (Siebenhandl et al., 2001). Tape ketan from two household producers in Bogor contained roughly 80–300 million lactic acid bacteria per gram, though these haven’t been tested as probiotics (Hasanah et al., 2019).
What You Need
- Glutinous (sticky) rice – white, or black glutinous rice (ketan hitam) for a dark purple, nuttier tapai. Regular rice doesn’t work well.
- Ragi tapai – sold in Indonesian, Malaysian and Chinese grocery stores as “ragi tape”, “tapai yeast” or “yeast balls”. Old or poorly stored ragi ferments weakly.
- A steamer, a clean glass or ceramic container, and banana leaves if you want to wrap portions traditionally.
Keys to Good Tapai
- Steam, don’t boil. Soaked, steamed rice stays in separate grains that the mold can colonize; boiled rice turns gluey.
- Cool to warm, not hot – below about 35°C (95°F) before adding the ragi, or the starter can die.
- Keep it warm: about 28–32°C (82–90°F), warmer than most ferments. An oven with only the light on, or an insulated box, helps in cool kitchens.
- Clean hands and tools. The ragi should dominate; stray microbes are what spoil tapai.
- Leave it alone for the first day or so.
What’s Normal – and What Isn’t
- Normal: a fine white, fluffy growth over the rice in the first day or two (that’s the starter mold), sweet syrup pooling in the container, softening grains, and a sweet, fruity, slightly alcoholic smell.
- Discard it: black, green, pink or orange mold, sliminess, or a rotten or strongly sour-vinegary smell instead of sweet and fruity.
- Too sour or strong: it fermented too long or too warm – refrigerate sooner next time.
- Not sweet after 3 days: the ragi was weak or old, or it was too cold.
How Tapai Is Eaten
- As a snack or dessert on its own, often from a banana-leaf wrapper.
- In es tapai, an iced drink or dessert with syrup and coconut milk.
- Cassava tapai fried in batter (tape goreng) or baked into cakes.
- During Eid and other celebrations in Indonesia and Malaysia.
Tapai contains alcohol, and it gets stronger the longer it ferments, so it isn’t suitable for children, during pregnancy or for anyone avoiding alcohol. If you make cassava tapai, use sweet cassava and cook it thoroughly – see our fermented cassava guide.
Related rice ferments: Japan’s amazake, South India’s idli, and more in the world’s best fermented foods. Malaysia also ferments durian into tempoyak.