Résumé:
The aim of this work was to try to improve the organoleptic, bacteriological,
physicochemical properties and optimise the nutritional value of liquid yoghurt by adding
Propolis powder,Acacia arabica resin or both together at different concentrations. In terms of
this work, 6 yoghurt mixtures were formulated by varying the quantities of Propolis powder
and Acacia arabica resin powder.
The results of the microbiological tests on the raw cow's milk used to make the yoghurt
complied with Algerian regulatory standards. It is free from total and faecal coliforms, as well
as staphylococci and salmonella. The results for pH and titratable acidity, fat content and dry
matter content of the formulated yoghurts complied with Algerian regulatory standards (4.3 <
pH <4.6; 80 <°D<100).
Propolis has optimised some of the physico-chemical characteristics, such as dry matter
and mineral salt content, but only slightly, as well as the sensory properties of yoghurts,
particularly their smell. However, their bitter taste and powerful antibacterial effect,
particularly against lactic ferments (Streptococcus thermophilus and Lactobacillus bulgaricus),
has led to a significant reduction in the lactic bacteria in the yoghurt, to the point of making
them non-existent, which means that the yoghurt loses its pro-biotic properties at all the
concentrations used: 0.25g, 0.50g, 0.75g and 1g.
This undesirable effect made it impossible to incorporate Propolis into the yoghurt,
unlikeAcacia arabica resin, which stimulated the growth of lactic bacteria in the yoghurt,
acting as a prebiotic and improving the colour and texture of the yoghurt.
