This should not be done without adequate controls in place established by knowledgeable individuals. Probably due to the increase in pasta in the diet, pesto, a blend of herbs in oil, is becoming more popular. These products have similar hazards to those above and must be processed using the same guidelines. A possible process alternative for fresh pesto is freezing. From a food safety point of view, it is necessary to make the consumer aware of the hazards of refrigerated or frozen pesto.
Botulism is a hazard in oil-coated low acid foods.
The concern increases as the product is held for a longer time under fluctuating temperature conditions. Shelf life may be a problem due to active enzymes in the herbs which break down the tissues. Blanching will destroy the enzymes, but it changes the character of the herbs. There are several applicable rules for these types of products. These include the requirements for preparation facilities, sanitation, and protection of food.