Cynara cardunculus as a potential source of milk coagulating protease: Effects on physical properties of cow's milk

Abstract

In the present research study, Cynara cardunculus (wild cardoon) flowers were blended and extracted using different types of buffers (phosphate buffer; citrate buffer and distilled water) for different maceration times. The most reliable, quick and efficient buffer was found to be phosphate (pH = 6.5) with a 6-h maceration time, which was used throughout this study. C. cardunculus extract (CE) was found to have high clotting and proteolytic activities. The extracted enzyme was found to be very stable against a wide range of pH values as well as of temperature. The formation of milk gels prepared in the presence of CE with different types of milk was evaluated using dynamic rheology and Turbiscan. The evolution of both elastic (G') and viscous (G″) moduli was monitored with time. The values of the whole milk enriched with milk powder gels were higher. Coagulum stability was evaluated using Turbiscan. The textural properties and the curd-firming rate of coagulum were also determined. In conclusion, the prepared CE could be an efficient milk-clotting agent in the production of dairy products.

Keywords: Cynara extract; coagulation; milk; rheology; stability; texture; wild cardoon.

FIGURE 1

Evolution, with incubation time, of the coagulating activity (a), the proteolytic activity (b) and protein content (c) of crude extract at pH = 7(); pH = 6.5 () and pH = 5.9 ()

FIGURE 2

Temperature (a) and pH (b) effect on milk‐clotting activity of crude extract

FIGURE 3

Backscattering profiles of skimmed milk (a), whole milk (b), whole milk enriched with milk powder (5%) (c) and whole milk enriched with milk powder(10%) (d) coagulated with cynarase flower extract

FIGURE 4

Evolution of G′and G″ versus time during coagulation of skimmed milk (a), whole milk (b), whole milk enriched with milk powder (5%) (c) and whole milk enriched with milk powder(10%) (d)

FIGURE 5

Curd firming rates for different milks: Skimmed milk, whole milk, whole milk enriched with milk powder (5%) and whole milk enriched with milk powder(10%)