We do a semilactic set soft cheese using a vat pasteurizer. We pasteurize, cool and set cultures and add a small amount of rennet the first day, cut the curd and mold up the next morning. We are using Jersey milk and you cannot add enough rennet to keep the cream from rising short of quantities typical of rennet set cheeses. So on the second day before we cut the curd we skim the cream. It makes great cultured butter, but our dairy inspector says we cannot sell it because the milk was only pasteurized at 145degrees and the pasteurization temperature for cream is higher, 155. This does not make sense to me. Has anyone experience with similar problems? We hate to throw the cream away and it is difficult to incorporate into the curd by stirring, the curd is very fragile.
I don't have an answer to your question, but I can say that your health inspector is apparently correct. Here is the applicable law (assuming you are in the US): https://www.law.cornell.edu/cfr/text/7/58.334 (https://www.law.cornell.edu/cfr/text/7/58.334) I wonder why the temp for cream is higher... Also interesting to see that the temp for frozen cream is even higher.
In the UK, it seems that cream needs to be pasteurised at 63C for 30 minutes (which is 145): https://www.legislation.gov.uk/uksi/1995/1086/made (https://www.legislation.gov.uk/uksi/1995/1086/made) (search for "Part II" and "Pasteurised Cream"). It requires ice cream to be pasteurised at 65C (which is 149). Again, not sure what the difference is.
Although it doesn't help you at all, barring discovering a reason for the increased temperature, I will suggest that these regulations were probably lobbied by the milk industry itself. I've seen this in Canada. For example, it was at one point illegal to sell unhomogenised milk in containers of less than 25 litres in Ontario (not sure what the regulations are right now -- that was nearly 20 years ago). I did some poking and it turned out that the milk industry lobbied for that regulation as a means to make it difficult for small dairies to break into the market. It meant that you couldn't sell milk unless you could afford the homogenisation equipment. The reasons for the different temperatures may literally be in order to stop you from doing exactly what you want to do. If you were bigger, you could standardise your milk, and pasteurise the cream separately.
I think the long term non-technical solution would be to contact any industry groups in the US representing small dairies and see if you can band together into a relevant political force. I suspect it will take 10 years or more and a *lot* of money to fix the problem, though. If you have access to a law library, you can work back year on year until you see what year the law was added and then find out what the rationale was (that's what I did when I was trying to find out what was up with the homogenisation issue in Ontario). Ideally your country will have all your laws available to you online which can speed things up, but I'm not sure if that's the case for the US.
Do you have the ability to run the warm milk thru a seporator and then pasturize the cream separately?
OK, I read the Federal regs. Paragraph One is the definition of butter, essentially 80% milk fat, but interestingly it starts out by saying that butter can be made from milk, or cream, or a combination of milk and cream. Then Paragraph Two tells you how to pasteurize raw cream. You don't need to be told how to pasteurize raw milk, you learned that in the previous section. So I would submit that I am making butter from raw milk, not from raw cream in compliance with the regs which say you can make butter from milk. I think the point here is that milk fat diluted in milk can be successfully pasteurized at a lower temperature than milk fat when concentrated in cream, same for milk protein evidently.