Updated: Aug 31, 2020
We had a slow vat yesterday.
Poor Stuart, he was in at 7am, hosing down the vat and setting off the pasteuriser. We really should have finished washing down by late afternoon, but it didn’t work out that way.
I was talking to my friend, John the Cheese Maker today for some advice about slow vats. We came up with four reasons why your vat may be slow:
Phage – or to give it its proper name is bacteriophage and is a virus which attacks starter culture. Many starter cultures are formulated to be phage resistant.
Antibiotics – antibiotics are ‘programmed’ to kill bacteria, and whilst we want a certain type of bacteria that encourages the acidity that we need, antibiotics will kill this.
Ambient temperature – if the ambient temperature is too low, the starter will never really get going, it can die back and this can lead to a slow vat
Starter culture – not putting enough starter in the milk will not provide the wherewithal to get that acidity going or if the starter is ‘off’. Starter can go off, particularly if it has not been kept at the correct temperature.
What to do?
Phage: clean the vat down with a highly concentrated solution of hypochlorite. This will kill off any unwanted bacteria, but be sure to rinse down very thoroughly afterwards. According to my friend John, signs of not rinsing down properly include the curd sticking to the vat. It is possible to have a lab test for evidence of phage in a curd sample. Another thing is to rotate your starter culture so that it is not the same strain used all the time
Antibiotics: all milk producers know they must segregate any cows’ milking who have received antibiotics. We ask our suppliers to sign a statement acknowledging this and outlining their policy
Ambient temperature: ideally keep the dairy warm. We can’t do this as we do not have heaters, but we do keep the curd warm by flashing the vat on and off
Starter culture: I think this may have caused our slow vat today. We tried a new starter culture for the first time and having asked the supplier for their recommended dosage, we followed this, but the acidity build up was so darn slow, it was tremendously frustrating