Effet de l’incorporation de deux extraits (extrait polyphénolique et jus frais) de la caroube verte sur la coagulation du lait (cas du yaourt).

Abstract

Carob is considered as a potential source of natural antioxidants (polyphenols). Indeed, researchers and manufacturers in food industry give an increasing importance for polyphenols due to their antioxidant properties, their great abundance in our diet, and their crucial role in the prevention and treatment of several diseases. Thus, recent interest from consumers for functional foods and the need to replace the synthetic antioxidants by natural antioxidants has led to the use of these molecules to formulate new products. The combination of antioxidant components from some fruit with milk proteins is the best example that has been reported by several authors. The objective of the present work is the polyphenolic assessment of green carob’s extracts (Polyphenolic extract and juice extracted from the fresh pods) and study the possibility of their incorporation in a formulation of a yogurt and their effects on the precipitation of milk proteins. This is mainly motivated by the research of a wide range of rich or enriched foods in polyphenols, particularly in case of dairy products. The evaluation of polyphenols in the studied extracts gave high contents of phenolic compounds namely total polyphenols, flavonoids and tannins. Therefore, the assessment of antioxidant activity, by DPPH andironreducing power tests, depicted a high antioxidant activity for both extracts. Green carob is therefore considered as an important source of natural antioxidants. Coagulation test revealed a precipitation of proteins with the juice at a level of 10%. The latter allowed to obtain a dense coagulum with a slight whey syneresis. In fact, juice from green carob seems to be more appropriate as a coagulating agent of milk protein in dairy industry, especially in yoghurt production. Physicochemical analyses of the obtained coagulum showed a pH of 5.07, an acidity of 63,66 ° D and a total dry extract of 22,74%. This coagulum is significantly different from the control yoghurt. Microbiological analyses reported that the coagulum formulated showed a good stability towards pathogens and germs of contamination.