Effect of chemical composition on the buffering capacity of selected dairy products

الملخص EN

Eight locally-produced dairy products were used in the study : yoghurt, labneh, Nabulsi cheese, dried and liquid jameed, acidic whey, cream and cow’s milk.

For each product, the in vitro acid-buffering capacity (BC) was determined, using a 5 % (dry matter) aqueous suspension titrated with 0.1N HCl until the pH reach 1.5 and then back-titrated to pH of 10.0 by addition of 0.1N Na OH.

BC values were calculated by dividing the treatable acidity of each sample by the change in pH units.

The resultant BC values were highest for whey, liquid jameed yoghurt and cream (2.45–4.86), intermediate for milk, labneh, dried jameed and the commercial antacid (1.50-2.25) and lowest for Nabulsi cheese (0.57).

These values showed a varying degree of correlation with the content of protein, ash, Na, K and P, and alkalinity of the ash (R = 0.99, 0.67, 0.72, 0.60, 0.59 and 0.42 respectively), while the weakest correlation was with aspartic acid content (R = 0.20).

In general, the BC values obtained appeared to be largely due to differences in the studied dairy products chemical composition.

Possible reasons are discussed for observed variations in pH among the products tested, when an acid or alkali was added.