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Cheese from Netherlands, polder districts around Leiden in the Oude Rijn basin

Leidse Kaas PDO (Boeren-Leidse met sleutels)Boeren-Leidse met sleutels

Semi-skimmed raw cow milk from no more than two milkings is set with rennet at 29–30 °C, cut, and warmed with hot water. Most of the curd is mixed with cumin seed, about 75 g per 100 L of milk, while a little plain curd lines the faces, and the cheese is pressed in two stages and stamped with Leiden's crossed keys. It is brined 5–6 days in 20 °Bé brine, its rind is coloured red with annatto, and it ripens at 12 °C or more.

Fully documentedCheese18 days – 19 daysPDO 'Boeren-Leidse met sleutels' (EU, 1997); also a 'Leidse Boerenkaas' under the TSG 'Boerenkaas'Family: Washed-curd cheese family (Gouda as template)

Recipe

Leidse Kaas PDO (Boeren-Leidse met sleutels), a photo from Wikimedia Commons
Photo: AlexanderVanLoon, CC BY-SA 3.0, via Wikimedia Commons
Amounts from a sourceThe PDO gives one dose, cumin at about 75 g of seed per 100 L of milk; everything else is a limit, not a recipe.
Raw cow milk, semi-skimmed, from no more than two successive milkingsMilk not used at once is cooled to 10 °C or less; under the TSG it may not be heated above 40 °C and must be made into cheese within 40 hours[leidse-pdo][boerenkaas-tsg]
Mixed culture of acid-forming bacteria (lactic, propionic and aroma-forming cultures are allowed)[boerenkaas-tsg]
Rennet[leidse-pdo][boerenkaas-tsg]
Cumin seedAbout 75 g per 100 L of milk[leidse-pdo]
Salt, as brine[leidse-pdo]
Annatto or a red to red-brown rind treatment[leidse-pdo]
Startera mixed culture of acid-forming bacteria (TSG Boerenkaas)

Total time across the recorded steps: 18 days – 19 days

Start
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up to 10 °C

What changes: Raw milk from two milkings is chilled and part of its cream is taken off

Step 1 of 7
Cool and collect the farm milk
Time
Not documented
Temperature
up to 10 °C
Set
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
Lactic acid bacteria

Milk from not more than two successive milkings, part-skimmed. Under the TSG it must be made into cheese within 40 hours of milking.

Flavour
Not documented
Texture
Not documented
Colour
Not documented

Microbes at work in this step

Not documented for this step.

Method

Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source

At a glance

Semi-skimmed raw cow milk from no more than two milkings is set with rennet at 29–30 °C, cut, and warmed with hot water. Most of the curd is mixed with cumin seed, about 75 g per 100 L of milk, while a little plain curd lines the faces, and the cheese is pressed in two stages and stamped with Leiden's crossed keys. It is brined 5–6 days in 20 °Bé brine, its rind is coloured red with annatto, and it ripens at 12 °C or more. Made in 7 steps over 18 days – 19 days. The longest step, colour the rind red and ripen, takes at least 13 days (Hoofdproduktschap voor Akkerbouwprodukten 1994) and runs at at least 12 °C (Hoofdproduktschap voor Akkerbouwprodukten 1994). Salt is 18–22 % (RVO (Netherlands Enterprise Agency)). A mixed culture of acid-forming lactic bacteria; propionic and aroma-forming cultures are also allowed does most of the fermenting.

Key numbers
Main stepat least 13 daysSet[leidse-pdo][boerenkaas-tsg]Colour the rind red and ripen
Temperatureat least 12 °CSet[leidse-pdo][boerenkaas-tsg]Colour the rind red and ripen
Salt18–22 %Set[boerenkaas-tsg]Brine
AciditypH 5.2–5.3Set[boerenkaas-tsg]Colour the rind red and ripen

What makes this one different

Unlike Gouda boerenkaas, which is full-fat (at least 48 % fat in dry matter), Leidse is made from part-skimmed milk, so it is lower in fat (30+ or 35+). It carries cumin, mixed into the curd but kept off the faces by a layer of plain curd. Its red annatto rind and key stamp mark it out.

Fat
Fat in dry matter 30–40 % in the PDO; the TSG table gives 30+ or 35+ for Leidse
Moisture
At most 45 % at 12 days (TSG Leidse Boerenkaas)
Shape
Flat cylinder with angular edges (the 'Leids model')

Related ferments

Safety

The cheese is made from raw milk. Under the TSG the milk may not be heated above 40 °C, must be cheesed within 40 hours, and the cheese ripens at least 13 days at 12 °C or more, with a pH of 5.20–5.30 at 12 days. The US FDA says ageing raw-milk cheese for 60 days may not remove E. coli O157:H7 and Salmonella. The CDC says people at higher risk, including pregnant women, people 65 or older and people with weak immunity, should avoid raw-milk cheese unless it is heated to 165 °F (74 °C) or until steaming hot.

History and sources

Every number is labelled with how it is known. How this atlas is made

The PDO file quotes a German cheese handbook that Leiden cheese was marked with the city's crossed keys and may be the origin of Norway's nøkkelost. It was traded in Leiden from the 17th and 18th centuries and, being part-skimmed, kept well as ships' provisions. The cheesemakers' association was founded on 28 October 1927, and the name was registered as a PDO in 1997.

  1. [leidse-pdo] Hoofdproduktschap voor Akkerbouwprodukten 1994, Application for registration under Article 17 of Regulation (EEC) 2081/92, PDO 'Boeren-Leidse met sleutels', EEC No G/NL/00316/94.01.26 (English summary sheet), registered by Regulation (EC) 1065/97spec
  2. [boerenkaas-tsg] RVO (Netherlands Enterprise Agency), Productdossier Boerenkaas (Gegarandeerde Traditionele Specialiteit), table of characteristics for 'Leidse Boerenkaas' and production methodspec
  3. [wp-leyden] Wikipedia, Leyden cheese (supports only the butter-making by-product origin of the part-skimmed milk and the keys from Leiden's coat of arms)wiki
  4. [fda-rawcheese2016] US Food and Drug Administration 2016, FY 2014–2016 Microbiological Sampling Assignment Summary Report, Raw Milk Cheese Aged 60 Daysgov
  5. [cdc-listeria] US Centers for Disease Control and Prevention, Preventing Listeria Infectiongov