Variables affecting the physical properties of Mozzarella cheese were investigated. The effects of various milk-clotting enzymes were examined. The type of milk coagulating enzyme used played a significant role in determining physical properties of direct acid Mozzarella cheese. Cook color was not affected by enzyme type, but melt and stretch were significantly affected. Proteolytic nature of starter cultures was reviewed and recommendation s were give n. Cheese made with proteinase-deficient strains had more stretch after holding for 14 and 28 d than cheese made with non-deficient strains. Cheese made with pairs or single strains of L. helveticus had the same melt, more stretch, and less cook color than cheeses made with paired strains of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus salivarius ssp. thermophilus. Frozen storage, thawing, and shredding of Mozzarella cheese were described and suggestions given for optimizing shelf life. Shredding, freeze temperature, thaw temperature , and time of storage had no effect on cook color. Frozen, shredded cheese stretched more and melted less than non-shredded frozen cheese. Reduced fat, high moisture Mozzarella cheese was made and found acceptable when compared to low moisture part-skim Mozzarella cheese. Reduced fat cheeses decreased in stretch and increased in melt throughout storage. Differences in stretch, melt, and cook color were not significant from one casein-to-fat ratio to another. Reduced fat, high moisture Mozzarella cheese was made with partial or total replacement of L. helveticus with L. casei ssp. casei and was found to compare well with low moisture part-skim Mozzarella cheese. Cheese made with L. casei ssp. casei cultures, paired with either S. salivarius ssp. thermophilus and L. helveticus or just S. salivarius ssp. thermophilus, had the least stretch and the greatest melt.