اسماعیل قنبری شندی

Nowadays, use of non-additive food products has become a fundamental issue and a general demand for consumers. On the other hand, the rheological properties and viscosity of beverage products are one of the important factors that impacts acceptability of these products. Hence, it is essential to find a way to solve this problem and improve the quality properties of juices.

In this study, the effect of homogenization with 5,000 and 10,000 rpm at 5 and 10 minutes was studied on the physico-chemical and rheological properties of peach nectar.

Homogenization significantly increased the apparent viscosity of the samples by 5% level, therefor from 10.6 mPa in the control sample, it was 16.67 mPa in the homogenized sample at 10,000 rpm and 5 min. On the other hand, homogenization improved color characteristics and peach nectar sedimentation as compared to the control sample. In addition, homogenization increased pH, brix, formalin index, and turbidity significantly. However, acidity of the samples increased insignificantly. Besides that, the particle size decreased significantly by the homogenization procedure.

According to the results of this study, it might be concluded that the application of homogenization improves the viscosity and stability of treatments and therefore the homogenization process can be used as a substitute for viscous additives.

In this research، the effect of xanthan gum in three concentrations of 0. 02، 0. 05 and 0. 07 g/kg of skim milk، containing 0. 4% fat in production of Iranian white cheese was investigated. Two control cheeses was prepared، that one of them was full-fat control cheese without gum which was made of milk containing 3. 2% fat and full milk. The other one was reduced fat control cheese that made of skim milk containing of 0. 4% fat without adding any gum. The results of chemical، textural and rheological experiments showed the improvement of cheese''s texture by increasing of xanthan gum. In this research، the full fat control one had the least quantity of rheological، textural features، and G* that showing the softness and desirability of texture. The treated cheese with xanthan gum of 0. 07g showed the maximum similarity to full fat control cheese which by increasing of xanthan concentration، the textural and rheological features reduced. The reduced fat control cheese had the highest quantity of and G* which showing the hardness and undesirability of texture. This study shows the desirability of xanthan gum as fat replacer in order to lowering the energy- producing extent of cheese as well as an improving factor of texture.