Rheological characterization of functional walnut oil-enriched butters stabilized by the various polysaccharides

ABSTRACT

Dynamic rheological measurements provide a valid determination of the ability of polymeric ingredients to compensate the reduced contribution of fat to texture and mouthfeel, as well as provide an emulsion that easily breaks down in commercial low-fat butters. In this study, the linear effects of pectin (PE, 0.5%) and xanthan gum (XG, 0.1%) and their interactions with locust bean gum (LBG, 0.2% and 0.4%), sodium-alginate (ALG, 0.2% and 0.4%), and modified starch (MS, 0.2% and 0.4%) on the flow behavior, dynamic rheological characteristics, and stability of reduced-fat butters containing 10% walnut oil (WO) were investigated. Results showed that the power law model can adequately fit the shear-rate/shear-stress data (0.888 ≤ r ≤ 0.992, p < 0.01). Flow behavior index of all the butters was approximately in the range of 0.6–0.9, which corresponds to pseudoplastic behavior. They behaved like an elastic solid with G′ > G″ at all frequencies. The samples prepared with PE–LBG (0.2% and 0.4%) and XG–ALG (0.4%) had the highest G′ values. The phase angle (G″/G′) decreased with increasing frequency from 0.03 to 15 Hz. The maximum apparent viscosity and stability were, respectively, found for WO butters formulated with XG–0.2% ALG and PE–0.4% LBG.

GRAPHICAL ABSTRACT

KEYWORDS:

• Butter
• emulsion stability
• microstructure
• pectin
• rheology
• xanthan

Acknowledgments

The authors also grateful to Eng. Jahanbakhsh for his kind assistance during the experimental phase.

Additional information

Funding

The authors would like to extend their appreciation for the financial support provided by the University of Tehran, ZamZam Co. (Tehran, Iran), and Iran Dairy Industries (Pegah, Tehran).