Traditionally, thistle rennet was prepared on Individual farms. Farmers would collect the thistle flowers and dry it. The dried flower would then be pulverized with a mortar and pestle and then steeped in hot/warm water to make a ‘tea.’ The amount of ‘tea’ added to the milk in the cheese recipes would require a great amount of trial and error, as the enzyme activity in the ‘tea’ would vary from year to year and from person to person preparing the ‘tea.’ This “home” process could lead to a rennet having a very high activity or a low activity. The variation in the activity of homemade thistle rennet may be one of the primary reasons that it is often reported as causing bitter flavors. Bitter flavors are often the result of overdosing the protease. This is reported in other industries doing protein hydrolysis.

Until now, the expansion of the thistle cheeses has also been held back by regulatory issues. Rennets must be approved by the various regulatory bodies, which made it difficult to produce cheese for sale beyond the local farm. As of 2015, this is no longer an issue for Thistle Rennet in the USA and Canada. Both countries approved the use of thistle rennet in cheese, as long as the rennet is produced in a facility that meets food grade processing requirements. Thistle rennet is also included with the recent EU dossier submissions on the use of enzymes in food processing.