If you wish to keep the blend a secret, patenting is not a good idea. Patenting publishes the mixture and the patent expires. What businesses do these days is to designate it "intellectual property" and "proprietary manufacturing secret".
As a rule, to patent something it needs to be
>>A new invention (utility patent) >>A patentable improvement on an existing invention (improvement patent) >>A unique design (design patent). >>A unique GMO creation for a plant (plant patent).
You need to be able to establish a numeral patent category and then research the entirety of that numeric category to establish that it has never been done before, or, if it's an improvement patent, research the entirety of the numeric category that the original patent belongs to to make sure no one has already filed for the improvement you're filing for. Same level of research goes into a design patent.
Prepare and file an application at the USPTO. Prosecute it to issuance or abandonment. I strongly encourage you to contact a patent agent or a registered patent attorney. Patent laws are complex and very unforgiving. You will need help. If you want to get more info, go to uspto.gov and look around.