Making

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Specific:
◦ Blue Mould
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Equipment

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Animal Based Rennet

This webpage is divided into the following topics:

1. General
2. Formats
3. Concentration
4. Storage
5. Amount
6. Preparation

General

Animal based rennet is made from the abomasum of un-weaned milk fed calves. The abomasum is also known as the fourth stomach, and in young animals, the “rennet-bag” or “vell”. The tissue secretes acids and the rennet enzymes chymosin and pepsin. New-born calves have 95% chymosin (sometimes referred to as rennin) and 5% pepsin, as the animal ages and its diet changes from milk to grass, the ratio changes such that at about nine months of age ratio has reversed to 10% chymosin and 90% pepsin.

Animal based rennet typically contains 90% chymosin and 10% pepsin in purified form and is considered by many to be the preferred rennet. Different ratios are available such as 92-85% chymosin and 8-15% pepsin.

Note, calf based rennet does not qualify for some diets and may concern some for animal welfare reasons.

Formats

Animal derived rennet is normally available in a liquid, paste, or powder formats with liquid being the most common by far.

Liquid format animal rennet contains, in addition to the enzymes chymosin and pepsin, trace proteins, sodium chloride brine, acetate, propylene glycol, caramel color, and flavour preservatives sodium benzoate, and potassium sorbate.

Powdered format animal rennet contains, in addition to the enzymes chymosin and pepsin, sodium benzoate and sodium chloride.

Manufactured liquid calf based rennet is often shipped in large ie 5 US gallon containers, and thus Hobby Cheese Making Supply stores often repackage into smaller containers.

Note, rennet paste is normally animal based and made of ground stomachs and brine. As it uses the whole stomach it is also rich in lipase which results in a piquant cheese such as Feta, Provolone, and Romano. Another choice is to use liquid refined rennet and dried lipase.

Concentration

Liquid calf rennet is normally in a very concentrated form because when diluted, the enzymes become unstable and lose strength .

Liquid calf based rennet is normally available in single, double strength, and triple strength. To complicate matters, single strength in Europe is different from that in USA.

In the mid 1990's a new standardization measurement (IDF Standard 157:1992) for rennet was adopted based on IMCU/mL or International Milk Clotting Units per ml of milk.

Storage

Most calf based based rennet manufactures recommend:

1. For liquid calves rennet, store at temperature below 3-7C / 38-45F, i.e. in household fridge, not in normally warmer cheese cave. Store away from direct sunlight to preserve maximum activity (ultra-violet rays in sunlight destroy the rennet activity). Product's strength will decline at 0.5% per month if ideal storage is followed for all times between manufacture and use.
2. For powdered calves rennet, store at 38 to 45°F in closed container away from sunlight. This can give high, greater than 1 year shelf life.

Amount

As rennet can come in different strengths, any specified amount of rennet in a cheese making procedure should be ignored and the amount of rennet used per volume of milk based initially on the manufacturer's directions. These directions can be found either on the product's container or from their website (many of these files are posted in CheeseForum.org's Library in the Forum). This amount should be increased or decreased with the users experience and results with the type of milk they are using.

Note:

• Rennet degrades based on age and storage best practices, adjust as appropriate.
• In general, store bought manufactured pasteurized and homogenized milk is requires more rennet than raw milk.

Preparation

1. For single strength liquid calves rennet, dilute in cool un-chlorinated water at ratio of 15-20 parts water to 1 part rennet by volume.
2. For powdered calves rennet, dissolve in 400 times it's weight of non-chlorinated cool water, let sit for 30 minutes with occasional agitation for complete dissolution.