In the United States, no more than 0.1% is allowed in fruit butters, jellies, preserves, and related products.[18] Up to 0.4% has been studied in low-salt, naturally-fermented pickles, and when combined with calcium chloride, 0.2% made "good quality pickles."[19] Potassium sorbate has about 74% of sorbic acid's anti-microbial activity.[17] When calculated as sorbic acid, 0.3% is allowed in "cold pack cheese food."[20] The upper pH limit for effectiveness is 6.5.[17]