Protein ingredients derived from milk are commonly used as food emulsifying agents while polysaccharides are added as stabilizers to develop low-fat emulsions. Functional properties of each one are advantageous when a protein/polysaccharide mixture is employed instead of some natural or modified polysaccharides with emulsifying properties that generally provide low viscosity. Some studies on emulsions containing milk protein/xanthan gum mixtures have been developed. They were focused on the influence of hydrocolloids concentration, through the determinations of droplet size, microscopic structure and creaming, and very few of them were conducted on the rheology and the preservation of consistency during storage. So, in this study oil in water emulsions (30% w/w) containing mixtures of milk proteins with xanthan gum were rheologically characterized at ambient temperature and the evolution of their rheological properties was measured during a month under cold storage. The commercial milk proteins used were sodium caseinate and whey concentrate at 2% mixed with xanthan gum at 0.3% or 0.5%. Emulsions properties were compared to those of respective aqueous systems and in general showed same rheological behaviour (power law) as their respective aqueous system, however, emulsions presented higher consistency index as expected, due to oil droplets concentration. The flow behaviour index showed a small variation, increasing its value slightly. The consistency of emulsions with xanthan gum and sodium caseinate or whey concentrate was similar, independently of the milk protein used, confirming that xanthan rheology predominates on emulsion rheology. Rheological parameters of emulsions stored during a month remained constant when mixtures of sodium caseinate/xanthan gum were used; however, emulsions with whey concentrate and xanthan gum mixtures showed more fluctuations between replicates that were accentuated in the third week of storage.
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