Plant proteases as milk-clotting enzymes in cheesemaking: a review

Plant proteases used as milk coagulants in cheesemaking are reviewed in this paper. Plant proteases have been used as milk coagulants in cheesemaking for centuries either as crude extracts or in purified form. These coagulants are an alternative to the calf rennet due to the limited availability and high price of rennet, religious factors, diet or ban on recombinant calf rennet in some countries. These enzymes are found in almost all kinds of plant tissues and can be obtained from their natural source or through in vitro culture to ensure a continuous supply of plant proteases. Almost all the enzymes used as milk coagulants belong to aspartic proteases, but enzymes from other groups such as cysteine and serine proteases have also been reported and possess the ability to clot milk under proper conditions. The excessive proteolytic nature of most plant coagulants has limited their use in cheese manufacturing due to lower yields of cheese, bitter flavors and texture defects. The search for new potential milk-clotting enzymes from plants still continues in order to meet the increasing global demand for diversified and good quality cheese production.