EFFECT OF SOME TECHNOLOGICAL TREATMENTS ON THE MINERAL BALANCE BETWEEN THE SOLUBLE AND COLLOIDAL PHASES OF CAMEL MILK

In dairy technology, mineral equilibrium in milk is important for understanding milk properties and for optimizing milk processing. The objective of this study was to examine the effect of some technological treatments (acidification, cold storage and heat treatments) on the mineral balance between the soluble and colloidal phases of camel's milk by using ultracentrifugation technique. The results showed that, as the pH reduced, the calcium (Ca), phosphate (P), magnesium (Mg) and citrate (Cit) present in the colloidal phase of camel's skim milk (CSM) were gradually displaced into the soluble phase. When the pH of CSM decreased to 4.7, the almost colloidal Ca and P were solubilized (more than 92.2 and 93.5%), respectively. Moreover, the colloidal Mg and Cit were totally solubilized at pH 5.2 and remained constant until pH 4.7. Furthermore, at this pH value small amounts of Mg and Cit were bound to colloidal casein (1.5-3%), respectively. Also, at pH 4.7 the ratio of colloidal Ca/P decreased from 2.07 to 1.68. On the other hand, the results affirmed that the cold storage of CSM at 4 ºC over a period of 7 days had marked influence on the concentration and distribution of Ca, P, Mg and Cit in camel milk. After 7 days of cold storage at 4ºC of CSM there were an increase in the soluble Ca, P, Mg and Cit contents by 11.9, 10.5, 5.3 and 9.0%, respectively. Furthermore, increasing heating temperature caused a significant decrease in the soluble Ca, P and Cit, but insignificant (p<0.05) effect on the Mg concentration was observed. Moreover, increasing heating temperature on CSM resulted in a significant decrease in the colloidal ratio of Ca/P from 2.07 to 1.64. Moreover, when CSM was boiled-treated, the soluble Ca, P, Mg and Cit concentration decreased by 6, 9.6, 5.6 and 8.5%, respectively. Pasteurization LTLT (Low-Temperature Long-Time) and HTST (High-Temperature Short-Time) led to a slight increase in the colloidal Ca, P, Mg and Cit concentration.