Several proteases from plant sources have been proposed as milk coagulants, however, limited research
has been done on their milk-clotting properties. The effect of temperature on the milk-clotting activity of
kiwi fruit, melon and ginger extracts was evaluated, as well as the effects of the different extracts on curd
properties. Melon extracts showed high milk-clotting activity over a broad temperature range (45–75 C)
while kiwi fruit and ginger extracts showed high activity over a narrower temperature range, with a maximum
at 40 and 63 C, respectively. Curds produced using kiwi extracts had textural properties comparable
with those obtained using commercial rennet, while melon extracts produced a fragile gel and low
curd yield. The milk-clotting behavior of the three plant extracts was related to the protease specificity
present in these extracts. The kiwi proteases displayed chymosin-like properties and thus hold the best
potential for use as a milk coagulant in cheese production.