Bulgarian dairy in the bakery: yogurt, sirene, kashkaval and urda

If Bulgaria has a single culinary signature it is dairy — and nowhere is that clearer than in its baking. The country gave the world its yogurt bacterium; its white cheese is written into a national standard; and almost every beloved bake, from the daily banitsa to the New Year table, is built on some combination of fermented milk and cheese. For a UK bakery serving a Bulgarian community, dairy is where authenticity is won or lost. This dossier is the working reference: what each dairy family does in the dough and the oven, the numbers that matter, how to substitute honestly with what a UK kitchen can order, and how it all wires back to the universal craft concepts in Pillar A.

We cover five families: kiselo mlyako (yogurt), sirene (white brined cheese), kashkaval (yellow cheese), urda/izvara (fresh and whey cheeses), and the fats — butter, kaymak and cream. (Overview: img-b6dib-08.)

1. Kiselo mlyako (кисело мляко) — the yogurt that leavens, conditions and moistens

The heritage — tell it, it sells. Bulgarian yogurt is not a marketing slogan; it is a documented scientific first. In 1905, Dr Stamen Grigorov, working as an assistant to Prof. Leon Massol at the University of Geneva, was the first to identify under the microscope the rod-shaped bacterium that ferments Bulgarian yogurt — the organism later named Lactobacillus bulgaricus. Ilya Mechnikov championed the discovery at the Pasteur Institute in Paris. Its symbiotic partner, Streptococcus thermophilus (classified by Sigurd Orla-Jensen in 1919), ferments the milk alongside L. bulgaricus. [c1] The national standard BDS 12 defines authentic Bulgarian yogurt as cow's, sheep's, buffalo or goat's milk fermented with a symbiotic culture of L. delbrueckii subsp. bulgaricus and S. thermophilus isolated in Bulgaria, from non-GMO milk, with no thickeners or milk powder added. This is the same lactic-acid-bacteria fermentation described in A2-sourdough-cultures-science — a living culture, not an additive. [c1][c2]

Authenticity & labelling note (flagged). BDS 12 is a Bulgarian national standard, not an EU/UK protected designation, so it confers no legal protection on the term "Bulgarian yogurt" outside Bulgaria; the standard was also revised in 2024 (the word "Bulgarian" was dropped from its title). Treat "Bulgarian yogurt" as a description of culture and method, and verify the current standard wording before any customer-facing label claim. The same 2024 title change applies to the sirene standard (BDS 15) below. [c2]

(Hero: img-b6dib-01; buffalo yogurt: img-b6dib-02.)

What it does in the bakery. Kiselo mlyako is the most versatile ingredient a Bulgarian baker owns, because it plays four roles at once:

1. It leavens. Its lactic acid reacts with bicarbonate of soda to release carbon dioxide — a gentle, instant chemical lift. The classic technique, seen in every mekitsi recipe, is to stir the soda into the yogurt and let it froth for a couple of minutes before mixing in the rest. This is the acid-base chemistry set out in A2-chemical-leaveners-baking-powder; get the balance wrong (too much soda, or too little acid) and you taste soap. (Reaction diagram: img-b6dib-09.) [c3]
2. It conditions the dough. Bulgarian baking-science writing is explicit that sour milk improves the dough's plastic, extensible properties and strengthens the fermentation — useful in enriched doughs and in the soft doughs pulled for mekitsi. [c3]
3. It adds moisture and steam. Its water flashes to steam in the oven, keeping banitsa and tutmanik interiors juicy rather than dry (see the oven behaviour in A5-baking-oven-science). [c3]
4. It brings tang. A clean lactic sourness that balances rich, salty cheese fillings.

Where it turns up: mekitsi (мекици — puffed fried dough leavened with yogurt + soda), banitsa fillings (see B6-banitsa-techniques), tutmanik and milinki (enriched cheese breads whose dough is mixed with warm yogurt), and kozunak (see B6-kozunak-enriched-bread). [c4] (Finished tutmanik cheese bread: img-b6dib-11.) Strained and salted, the same yogurt becomes katak (катък), a Rhodope spread — proof of how far one fermented milk stretches. (Katak: img-b6dib-07.)

Sourcing note. Use a plain, unsweetened natural yogurt with no gelatine or set-starch. Greek-style (thicker) gives a less runny filling. Kefir works as a cultured-milk alternative in soda doughs.

2. Sirene (сирене) — the white brined cheese that fills everything

Sirene is the savoury heart of Bulgarian baking — the cheese in banitsa, tutmanik and milinki. It has its own national standard, BDS 15:2010 (in force since 20 August 2010, replacing three earlier cow/sheep/mixed standards). Under it, Bulgarian white brined cheese is made from cow's, sheep's, buffalo, goat's or mixed milk; it is slightly crumbly with a minimum fat in dry matter of ~44-48% (44% cow/goat, 45% mixed, 48% sheep/buffalo); cow's-milk cheese has dry matter not less than 46%; salt is about 3.5% in the cheese (the brine runs 6-10%); and it is matured about 45 days (cow) or 60 days (sheep) at 10-12°C. [c5] (Sirene cubes: img-b6dib-03; block: img-b6dib-04.)

Sirene is not feta — and it matters. This is the mistake UK kitchens make most. Greek feta is a PDO cheese made chiefly from sheep's milk (up to 30% goat's); Bulgarian sirene is most often cow's milk (or mixed), and it is softer, creamier and milder/less tangy. If you cannot source genuine sirene, cow's-milk feta is the closest substitute — its milk base matches better than sheep's feta — but note the legal point: a cheese that is not Greek PDO feta may not be labelled "feta". [c6] See the full comparison in data.json → table-sirene-feta.

The salt rule (food-safety and seasoning). Because sirene already carries ~3.5% salt, do not add salt to a sirene filling until you have tasted it. The same figure is why a sirene-based bake counts as a high-salt line for nutrition labelling. [c5][c7]

In the Domson range the nearest stocked analogue is a grated white cheese, which you crumble/grate into fillings; for the most authentic result, pair it with imported Bulgarian sirene where you can.

3. Kashkaval (кашкавал) — the melting yellow cheese

Where sirene is the crumbly white filling, kashkaval is the melting yellow cheese — a semi-hard, scalded-curd (pasta filata) cheese in the same family as Italian caciocavallo and provolone. It too has a national standard, BDS 14:2010 (in force 15 November 2010). The defining step is parene — the curd is heated/steamed to 63-65°C measured at the centre of the cheese mass, then moulded, which gives kashkaval its dense, pliable, string-when-melted texture. The standard specifies thermized (heat-treated) milk, with no preservatives, emulsifiers or additives; the cheese is matured at least 45 days (cow's milk) or 60 days (sheep's and mixed), and stored at -2 to +4°C with a minimum 6-month shelf life (4 months for buffalo-milk kashkaval). [c8] (Kashkaval: img-b6dib-05.)

What it does in baking. Kashkaval is the gratin cheese. Grated and scattered over a tutmanik it melts and browns into a glossy, savoury top — and the professional trick, seen in Bulgarian recipes, is to add it near the end of the bake so it melts and colours without drying out. It is also the star of kashkavalki (кашкавалки — quick cheese balls/bites made from yogurt + soda + egg + grated kashkaval + flour) and appears in cheese tutmanik alongside sirene. [c9] See the formula card formula-kashkavalki and formula-tutmanik-cheese in data.json.

For a UK kitchen, a mild, good-melting yellow cheese is the working analogue: Gouda (block or grated) is the closest single cheese; a mozzarella or mozzarella/cheddar blend adds stretch and browning where you want a more molten top.

4. Urda / izvara (урда / извара) — the ricotta of Bulgarian baking

The fresh, mild, high-protein cheese that fills a sweet banitsa or milinki is izvara — and in some Bulgarian dialects the same product is called urda (урда). (This is a different cheese from the Romanian/Ukrainian Hutsul "urdă"; don't conflate them.) [c10]

Izvara is made two ways, and the distinction is worth understanding (process diagram: img-b6dib-10):

• Rennet-curdled (сирищно пресечена) — from skimmed milk set with lactic cultures and rennet, then drained and pressed. It comes in fat-free, semi-fat (min 9% fat) and full-fat (min 18% fat) grades.
• Heat-curdled (термично пресечена) — the true whey cheese: made from whey or buttermilk, whose whey proteins (lactalbumin and lactoglobulin) are precipitated by heating to about 90°C, then drained and pressed. This is the closest Bulgarian cousin to Italian ricotta.

Either way, izvara concentrates milk protein (casein, albumin, globulin) and is rich in calcium, phosphorus and B-vitamins. Under the older standard BDS 889-80 it has an acidity of 250-280°T, salt 1-2% and water 78-82%; small packs keep 72 hours at 2-6°C, large containers 4 months at 0-6°C. [c11][c12]

In baking izvara/urda is the mild, low-salt filling cheese: used sweet (with sugar, egg yolk, lemon and vanilla) for sweet banitsa, milinki and cheesecake, and savoury (on its own or blended with sirene) for banitsa and chushki byurek (чушки бюрек — peppers stuffed with cheese-and-egg, battered and fried). Because it is mild and creamy, it also replaces cream cheese/ricotta in desserts. [c13] (Chushki byurek showing cheese filling: img-b6dib-06; sweet filling formula: formula-izvara-sweet-filling.)

The genuine spec we can cite. The catalogue's Delikates Cream Cheese 15% (OSM Bieruń) is the best-documented izvara/fresh-cheese analogue we hold: pasteurised milk and cream soured with dairy cultures then concentrated — exactly the izvara idea — with water 71-73%, fat 14-16%, pH 4.6-4.8, a clean slightly-sour taste and a uniform, slightly grainy texture; 179 kcal, 7.6 g protein and only 0.23 g salt per 100 g; allergen: milk; stored +2 to +8°C for 40 days (48 h after opening). Curd cheese, ricotta or mascarpone all substitute in the same role. [c16]

5. Butter, kaymak and cream — the dairy fats

The last dairy family is the fat. Krave maslo (краве масло — cow's butter) is made from fresh or cultured (fermented) cream, and melted butter is the enriching and brushing fat of Bulgarian confectionery: it gives flavour, deep golden colour and richness to kozunak, banitsa and tutmanik. Kaymak (каймак) is a rich clotted-cream spread/topping, and smetana (сметана) the sour cream that enriches doughs and toppings. The choice of fat and its behaviour in the dough are the subject of A4-fat-types-and-selection and A4-butter-grades-and-specialist-types; here the point is simply that butter is the Bulgarian flavour fat (sunflower oil being the everyday crisping fat in filo work, per B6-banitsa-techniques). [c14]

The genuine butter spec. The catalogue's Unsalted Butter 82% (Polmlek), made from pasteurised cream, is 82% fat / 16% water, 744 kcal per 100 g, with 55 g saturated fat and only 0.20 g salt per 100 g. It carries the milk (lactose) allergen and must be stored 0-10°C, used within 60 days of production (or frozen -18 to -22°C for 12 months). For a laminated butter-dough bake, a higher-fat tourage butter is the roll-in choice. [c15]

On "cream" — read the label. The catalogue's Double Cream Bierunska UHT 33% (OSM Bieruń) is not a pure dairy cream: it is a cream-based blend enriched with palm-coconut vegetable fat (plus stabiliser, flavouring and colour), at 33% fat, 315 kcal per 100 g. It works as a pouring/whipping cream and as a kaymak-style enrichment, but if you need pure cream for authenticity or labelling, source accordingly. [c17] The other cream/sour-cream/curd lines are linked for sourcing in data.json → linked_products.

6. Buy it in the UK — the substitution table

The platform does not stock genuine Bulgarian sirene, kashkaval or izvara. The honest working plan is to build the structure from catalogue analogues and, where authenticity is critical, pair them with imported Bulgarian cheeses. The full mapping is in data.json → table-substitution and linked_products; in brief (chart: img-b6dib-12):

• Kiselo mlyako → Yoghurt Natural 3% (Figand) or Yoghurt Greek Style 3.5% (OSM Bieruń); kefir as a cultured-milk alternative.
• Sirene → White Cheese Grated (Lallemand) or imported cow's-milk feta.
• Kashkaval → Gouda block/grated; mozzarella or mozzarella/cheddar for extra melt.
• Urda / izvara → Delikates Cream Cheese 15% (OSM Bieruń, genuine spec), Curd Cheese FigAnd 4%, or mascarpone.
• Butter → Unsalted Butter 82% (Polmlek, genuine spec); Tourage Croissant Butter for laminated dough.
• Kaymak / smetana → Double Cream Bierunska 33% (blend) or Sour Cream FigAnd 18%.

Read data.json → formula-mekitsi-yogurt-soda, formula-tutmanik-cheese, formula-izvara-sweet-filling and formula-kashkavalki for worked formulas in baker's percentage (see A8-bakers-percentage-fundamentals and A8-enriched-dough-formulas).

7. Food safety and allergens (flagged for review)

Bulgarian dairy bakes carry the milk allergen throughout — sirene, kiselo mlyako, kashkaval, izvara/urda, butter and cream are all milk products. The doughs and kori add cereals containing gluten (wheat), and cheese-egg fillings (banitsa, tutmanik, milinki, kashkavalki, chushki byurek) contain raw egg before baking, so the product must be baked through to a set, safe interior before service. Because sirene carries ~3.5% salt, sirene-based lines are high-salt for nutrition purposes — do not add salt without tasting. Chilled dairy (butter, cream cheese, cream) must be stored to its datasheet (butter 0-10°C ≤60 days; cream cheese +2 to +8°C ≤40 days; cream 4-8°C ≤4 months) and held per your HACCP plan. These allergen, food-safety and nutrition statements must be confirmed against your own finished-product testing and the current supplier specifications before any customer-facing label or claim. [c15][c16][c17][c18]

8. A note on the catalogue spec data (honesty first)

Three catalogue dairy datasheets were read and verified as genuine, and their numbers are cited above and in data.json: Polmlek Unsalted Butter 82%, OSM Bieruń Delikates Cream Cheese 15% and OSM Bieruń Double Cream Bierunska UHT 33%. Five other dairy products carry mismatched spec PDFs — the attached file does not describe the product — so no spec values are cited for them and they are linked for sourcing only: Yoghurt Natural 3% (the PDF is a raisins datasheet), White Cheese Grated (a Lallemand yeast datasheet), Sour Cream FigAnd 18% (a raisins datasheet), Curd Cheese Bieruński Tray (an Allied Mills plain-flour datasheet) and Cheesecake Curd Cheese Wykwintny (a rapeseed release-oil datasheet). The operator should re-attach correct datasheets before any spec is quoted for those lines.

Cross-links

Pillar A craft concepts: A2-chemical-leaveners-baking-powder (yogurt-acid + soda lift), A2-sourdough-cultures-science (the L. bulgaricus + S. thermophilus lactic fermentation), A4-fat-types-and-selection & A4-butter-grades-and-specialist-types (butter, cream, kaymak as fats), A6-pastry-creams-fillings (cheese and cream fillings, avoiding curdling), A5-baking-oven-science (steam, melt and Maillard browning of cheese/butter), A8-enriched-dough-formulas & A8-bakers-percentage-fundamentals (reading the formula cards). Sister Bulgarian articles: B6-banitsa-techniques (sirene + yogurt filling), B6-kozunak-enriched-bread (butter and dairy in enriched dough), B6-filo-dough-kori (the sheets the fillings go between), B6-festive-baking-calendar (ritual and seasonal dairy bakes).