Quality ingredients are an essential part of making good cheese. Ingredients need to be predictable in their use. If they are not, then your cheese may not turn out as you want them to. There are many variables in cheesemaking that can affect how cheese turns out. Using old and unpredictable ingredients should not be one of those variables.
If you have been making cheese long enough, you will have come across cheesemaking ingredients in your fridge or freezer that will soon have reached or even passed their best before or expiry date.
There are only a handful of manufacturers across the world that manufacture starter cultures and ingredients for making cheese. There is not a lot of difference in the way the cultures are selected grown and distributed.
Lactic Starter Cultures
Lactic Starter cultures to make cheese come in various forms:
- Freeze dried (LYO) see definition below. Depending on the manufacturer they can be referred to as DVI (direct vat inoculation) or DVS (direct vat set).
- A liquid bulk culture that has been grown from a frozen or freeze-dried culture
- Back slopping of whey
- Frozen (requires storage at <60C)
- Raw milk incubation
Most home cheesemakers will be using freeze-dried cultures to make cheese. Some will also be growing their own liquid cultures, some back-slopping and using some raw milk. These methods require some degree of monitoring to obtain the correct end result and optimal activity. These processes will not be discussed in this article.
Starter cultures that are freeze-dried look like milk powder but are highly concentrated with bacteria. There is somewhere around the 1010to 1013 organisms per gram of powder. The technology used to make freeze-dried cultures has been used commercially since the 1970s. The cultures come with different recommendations on the actual shelf of the product. For example:
Company A storage recommendation: At least 24 months from the date of manufacture when stored according to recommendations. At 5°C the shelf life is six weeks.
Company B storage recommendation: 18 months from the date of manufacture at <= 4c
Company C storage recommendation: Cultures can be kept for six months without loss of activity if stored between 4°C– 8°Cand 12 months if stored at -18°C
There are various terms used: ‘best-before’, ‘date-of-manufacture’. The important issue here is can you still use your cultures after the end use date has been reached? By storing the cultures in the freezer, you are maximising their shelf life. There should be no loss of the culture’s viability if the culture is stored in the freezer and the freezer is operating correctly. Generally, the cultures will last for another several months. I think we have all used cultures in this way. After several months have passed their optimum performance may or may not have diminished, you simply cannot tell without some sort of technical analysis. So, you need to decide to continue to use those cultures or replace them with a new batch. At stake is a possibly inferior batch of cheese plus the cost of the milk and all the time put into making and maturing it.
Flavour and Ripening Cultures
Flavour and ripening cultures to make cheese usually come in these three formats:
- Freeze dried (LYO)
- Hyptonic (see below)
Most home cheesemakers will be using either the freeze-dried or the hyptonic formats.
Flavour and ripening cultures that are freeze-dried look like milk powder but are highly concentrated with. As in the lactic starter cultures, these cultures also come with different recommendations on the actual shelf of the product. For example:
Company A storage recommendation: culture can be kept for four months if stored at +4°C or
for six months if stored at -18°C,
Company B storage recommendation: 12 months from the date of manufacture at -18c or 2 months if stored at +4c
Company C storage recommendation: At least 12 months if stored below -18c
Flavour and ripening cultures can be quite varied in the type of microbe that is being used for bacteria, yeast, moulds etc. Due to this variation between organisms and each organism having different shelf life characteristics, the shelf lives between product s will also vary. So, a single shelf cannot be used against all of the ripening cultures you have. You are still maximising the life of your cultures by storing them in the freezer (unless they are specifically to be stored in the fridge). There should be no loss of the cultures viability if the culture is stored in the freezer and the freezer is operating correctly. Generally, the cultures will last for a few months after the best before date has been reached. Usually, I find they do not last as long after the best-before as is the case with the lactic cultures. After a few months past the best before date has been reached it is recommended that they are discarded, and a new batch used.
Rennet is such a key ingredient in making cheese that my recommendation is to make cheese using a rennet where the best before date has not expired.
Lipase can usually be stored in the freezer or fridge. It is very stable and can be stored for several months after the best before date has been reached.
Annatto has a shelf life of around 12 months from the date of manufacture. The deterioration is with oxidation. Some settling of the solids may also occur. Its function is to change the colour, so it is not going to change the functionality of the cheese. I find it will last for several months past the best before date.
Freeze Dried or the technically correct term is Lyophilised: Often referred to as ‘LYO’. Cultures are manufactured using a low-temperature dehydration process so that the heat used in traditional drying processes does not damage the bacterial cells. The bacterial cultures are grown in a liquid medium, but the acid is neutralised during the manufacture, again not to damage the bacteria cells. The incubated liquid is then frozen and then placed under a strong vacuum which lowers the temperature at which evaporation occurs. Evaporation of the moisture in the liquid occurs until the liquid portion a powder remains.
Hyptonic: The live cultures are stored in a liquid solution. The liquid is specially balanced to keep the cultures alive but also the keep the medium they are in from deteriorating with age. Salts and sugars are used in the liquid solution. The bacterial cells have membranes which are permeable to sugars and water diffusion, but which do not allow the storage solutions salts to pass. The cell membrane allows the cell to choose, using receptors and channels, the things it will let in, e.g. nutrients.