Abstract
Fruit extracts from Solanum esculentum, Solanum macrocarpon L. and Solanum melongena were tested for their milk-clotting potential. The release of substances associated with milk-clotting was highly dependent upon quantity of berries, extraction duration and sodium chloride concentration. The highest milk-clotting activity was obtained after 8 h (for S. esculentum and S. melongena), and 12 h (forS. macrocarpon) of soaking 20 g of fruit in 6% NaCl 4°C. In these conditions, there was a non linear relationship between the milk-clotting time and the amount of fruit extracts from each species. The loss of milk-clotting activity was dramatic after wet-heating of extracts from S. esculentum and S. macrocarpon at 80°C for 10 min and after dry-heating of fruits at 100°C for 24 h. Heat treatment did not significantly affect the clotting activity of extract from S. melongena. Fruit extracts from S. esculentum had the greatest milk-clotting activity followed by extracts from S. macrocarpon and S. melongena. Extracts from S. esculentum and S. macrocarponexhibited a proteolytic activity on the casein. Key words: Milk-clotting activity, S. esculentum, S. macrocarpon, S. melongena, fruit extracts.
Highlights
IntroductionCalf rennet was the first and still is the most widely used in cheese making around the world
Enzymatic coagulation is very important in the manufacture of cheese
The milk-clotting time is shorter with extracts from S. esculentum followed by those from S. macrocarpon and S. melongena
Summary
Calf rennet was the first and still is the most widely used in cheese making around the world. It is a milk-clotting enzyme preparation which is extracted from the calf’s fourth stomach. This enzymatic preparation contains chymosin, which exhibits specific and limited proteolysis of the Phe105-Met106 bond in kappa-casein. High specific milk-clotting activity of calf rennet prevents excessive proteolysis during maturation and ensures the correct ratio between protein and peptides. The world-wide increase in cheese production, alongside with the reduced supply of calf rennet, have led to an increase in the demand for alternative sources of milk coagulants (Cavalcanti et al, 2004). Consumer constraints on the use of rennets have led to a growing interest in vegetable coagulants
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