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.

Abbreviation

TA, Titratable acidity; LAB, lactic acid bacteria; MRS, Mann, Rogosa and Sharpe Agar; PDA, potato dextrose agar.