INTERACTION BETWEEN SOME PLANTS TANNINS AND MILK PROTEIN

Tannin fractions were isolated from walnuts (Juglans regia), green tea and lentil (lens culinaris L.), used tannin acid as standard. The total phenolic compound and condensed tannins content were determined of these tannins. It was found that the tannins from walnuts had the highest total phenolic compound and the lowest condensed tannins, while green tea had the highest condensed tannins. The interaction between tannins fraction from plant sources and tannic acid (as standard) with casein precipitated from skim milk (by acidification) was determined using precipitating potential method. The optimum pH of the interactions was at pH 5, while the lowest interaction was at pH 8. The highest precipitating potential was noted for tannic acid followed by walnuts, green tea and lentil. Moreover the tannins-casein complex was determined using fluorescence quenching method. The interaction between casein and tannic acid had the most extensive fluorescence quenching and it was in order walnut > green tea > lentil for plant tannins.