BUTTERMILK

While the name buttermilk traditionally referred to the liquid left after churning butter from naturally cultured or fermented cream, today it usually means a tangy, viscous cultured milk used as a substitute for milk in drinks, baking (scones, pancakes, soda breads, etc) and cooking (coated fried chicken).
Cultures – CHN-22 / XPL-1
Phage – R-703 / R-704 / R-707 / R-708

CRÈME FRAÎCHE

A French soured cream originally from Normandy (the town of Isigny-sur-Mer holds the product's only AOC), crème fraîche typically contains 30-45% fat and has a pH of 4.5. It is prized in cooking as it doesn't split when heated, while its rich, gently tangy character makes it popular for desserts.
Cultures –  CHN-22 / XPL-1
Phage – R-703 / R-704 / R-707 / R-708

QUARK (AKA TWARÓG)

Popular across northern and central Europe, Quark is a thick curd cheese made by fermenting soured milk with mesophile bacteria. It can be stirred, set or grainy and usually contains around 20% fat (though low fat versions are increasingly popular). Quark is used in sweet and savoury dishes.
Cultures –  CHN-22 / XPL-1
Phage – R-703 / R-704 / R-707 / R-708

COTTAGE CHEESE

Although technically a soft cheese, we've included cottage cheese here due to its loose texture and typical uses. Also known as farmer cheese or queso blanco, cottage cheese is a low fat (4%) partially drained, unpressed fresh curd cheese made with or without rennet – as reflected in the curd size.
Cultures – R-703 / R-704 (fast),
R-707 / R-708 (medium acidification)

FROMAGE FRAIS

Originating in northern France/southern Belgium, fromage frais is a soft, unripened cheese made from whole or skimmed milk. Under French legislation is must contain live cultures (otherwise it's fromage blanc). It has the consistency of cream cheese and a mild lactic tang, with a fat content of around 8%.
Cultures –  CHN-22 / XPL-1
Phage – R-703 / R-704 / R-707 / R-708

SMÈTANA (AKA TEJFÖL)

This thick soured cream is popular across eastern and central Europe. It's similar in style to French crème fraîche but smètana is lower in fat (typically 10-25%) and made by souring heavy cream. It's enjoyed in many savoury and sweet dishes, particularly pancakes, dumplings and meat stews. It doesn't split when heated.
Cultures –  CHN-22 / XPL-1
Phage – R-703 / R-704 / R-707 / R-708

CREAM CHEESE

Originating in Tudor England, fresh cream cheese transformed into the smooth creamy product we know today in 19th century New York. Made from acidified full-fat milk with cream added, cream cheese is high in fat (typically between 33% and 60%) with a rich, smooth texture and gently lactic tang.
Cultures –  CHN-22 / XPL-1
Phage – R-703 / R-704 / R-707 / R-708

KEFIR (AKA BÚLGAROS)

This distinctive fermented milk originates from the Caucasus mountains in Eurasia. Kefir 'grains' are curious, cauliflower-like clumps of lactic acid bacteria and yeasts that naturally occur in this region. Chr. Hansen's Kefir is a cultured form that transforms milk into a tangy and nutritious drink with consistently stable results. 
Cultures –  KEFIR1 / LAF-3 / LAF-4 / LAF-7
Phage – KEFIR2 / XPL-1

SOUR CREAM

Sour cream is a thick and tangy fermented cream that contains around 18-20% fat (although lower fat version can be made). Popular in central Europe and America as a cooking ingredient, sour cream splits if boiled so is added to dishes at the end of cooking (goulash, stroganoff, etc) or used in dips and toppings.
Cultures –  CHN-22 / XPL-1
Phage – R-703 / R-704 / R-707 / R-708

Bacteriophage (a.k.a. ‘phage’) is a tiny airborn virus that attacks the lactic acid bacteria in milk. The virus is present in nearly all dairy facilities due to its size and rapid reproduction rate. Phage infection typically results in slowed production times, reduced product quality and even complete batch loss.

The virus works by attaching itself to a lactic acid bacteria cell and injecting its DNA. It then takes over the cell’s metabolism to replicate new bacteriophage viruses, which are then released back into the dairy environment. Bacteriophage is the most common cause of failure during the acidification of milk in cheesemaking.

The best way to deal with bacteriophage (beyond heat-sterilising your milk, equipment and air to between 90 and 95°C) is to try and break the re-contamination / multiplying cycle. This can be done in a number of ways, and we'd advise you incorporate as many of these as possible into your dairy production routine:

Culture rotation
It’s good practice to rotate your cultures in conjunction with regular phage testing. Always have a back-up culture with a similar performance and use this as an alternative to your main culture once attack occurs. After testing, you can usually return to your original culture after three weeks.

For more serious phage attacks, you may need to introduce a continuous rotation of two to five different cultures, with a replacement schedule of every two to three days.

Controlling phage levels
It is safe to assume that some bacteriophage will always be present in your production, so it’s good practice to make monitoring part of your standard routine, on a monthly or weekly schedule (depending on your production size and frequency).

The two most common methods for detecting phage levels are the inhibition test and the plaque assay or 'spot' test.

Production
By using DVS cultures you can reduce the risk of phage infection by eliminating its propagation stage. Using phage-insensitive starter cultures in conjunction with a culture rotation system can significantly reduce the risk of contamination.

Sanitation
By thoroughly cleaning and disinfecting your equipment between uses as standard, you will limit the transfer of whey and cheese remnants from previous production batches. Remove all dairy remnants between fills and rinse cheese vats properly with water. This water should be collected and removed from the vat, followed by disinfection.

Facility design
Since bacteriophage can easily spread through air and water. it’s important that your production facilities are designed accordingly. Ideally this would involve circulating the air away from the cheese production area.