They have only one protein source and one carbohydrate source that the cats are unlikely to have ingested before.[15] Owners are more likely to be compliant when feeding a commercial novel protein diet than when feeding a home cooked diet.[2] This is due to the fact that it can be difficult to obtain novel proteins for food preparation,[15] and it takes less time to provide a commercial diet than to prepare a home cooked one.[8] In the early '90s, an experiment was performed showing that novel protein diets had a 70 to 80% success rate.[3] However, commercialized novel protein diets are not always effective, since they are not always tested on animals that have food sensitivities, and the manufacturing process of the diets can cause adverse reactions due to the inclusion of additives which may be allergens to some cats.[14] It is recommended that human-grade meat be used in the diet instead of pet food meats since pet food meats can include preservatives, which can be detrimental to the success of the diet.[15] Also, a study showed that if the processing machinery was not cleaned properly, ground meat that came from one animal could be contaminated with the ground meat from another animal.