Burong isda is a fermented mix of cooked rice, fish and salt from Luzon in the Philippines, best known in Pampanga. As lactic acid bacteria ferment the rice, the mixture turns tangy and savory, and the fish softens. It is usually cooked before serving and eaten as a side dish or condiment with grilled fish or meat and vegetables.
Because it combines fish, cooked rice and warm-room fermentation, burong isda needs more care than a vegetable ferment. This page gives a home recipe and puts the safety rules first.
How Burong Isda Ferments
The cooked rice feeds lactic acid bacteria, which sour the mixture and lower its pH. In a classic study of burong dalag (burong isda made with mudfish), Leuconostoc mesenteroides, Pediococcus and Lactobacillus plantarum drove the fermentation; the pH fell below 4.0 within about a week, and the jar had to be kept covered to stop yeasts and molds (Orillo & Pederson, 1968). A DNA-based study of Philippine fermented foods, burong isda among them, also found lactic acid bacteria dominant (Dalmacio et al., 2011).
Food Safety First
An FAO review of low-salt fermented fish names Salmonella, E. coli, Staphylococcus aureus and Clostridium botulinum as the hazards, and identifies the first days of fermentation, before the pH falls below about 5, as the critical window (FAO). Fish-and-rice ferments have a real botulism history: Japanese izushi, a similar preparation, caused 21 type E botulism outbreaks in Hokkaido between 1951 and 1965 (Nishiura et al., 2007). Egypt’s salted, ungutted mullet, fesikh, has caused type E outbreaks too. We found no documented outbreak linked to burong isda – but the same precautions apply.
- Use very fresh fish, kept cold until mixing. It should smell clean, never of ammonia.
- Weigh the salt. Don’t reduce it.
- Get it sour fast. Ferment in a warm-enough room (about 68–72°F / 20–22°C) so the pH drops quickly. If you have pH strips, it should be clearly below 4.6 within the first few days; if it isn’t, throw it away.
- Discard, don’t rescue: any mold, an ammonia, rotten-egg or putrid smell, or a slimy texture means the whole batch goes. Don’t scrape and eat.
- Cook it before eating, as is traditional, and refrigerate once it’s sour.
- People who are pregnant, elderly or immunocompromised should avoid home-fermented fish.
Making Burong Isda
The full recipe is in the recipe card above. Cooked white rice makes up the bulk of the mixture, with fish in bite-sized pieces and salt weighed at about 7% of the fish weight. Tilapia, catfish and milkfish (for burong bangus) are common choices; mudfish is traditional for burong dalag.
What to expect
Days 1–2: a mild sour aroma develops. Days 3–5: clearly sour and savory, and the pH should be well below 4.6. Days 5–7: the usual flavor window; refrigerate when you like the taste. In a cool room it takes a little longer, in a warm room less – but a batch that isn’t sour by day 3 shouldn’t be kept.
How to Serve Burong Isda
- Sautéed: fry a few spoonfuls in a little oil with garlic and onion until cooked through and fragrant.
- With vegetables: served with steamed or blanched vegetables such as mustard greens (mustasa), which are used to wrap bites of it.
- With grilled food: a sour, salty side for grilled fish, pork or chicken.
Storage
Once it’s sour, keep burong isda covered in the fridge and use it within a couple of weeks, always with a clean spoon. It can be frozen in small portions.
Related Filipino ferments: balao-balao (fermented shrimp and rice) and atchara (fermented papaya relish). For other fish ferments, see our guide to fermented fish sauce. Thailand’s naem is a similar rice-soured ferment, made with pork.