Effect of zinc fortifications on rheological properties and micro-structure of water-in-oil spreads containing κ-carrageenan

Abstract

Work was undertaken to investigate the effect of zinc fortification (up to 15 mM) on the rheology, firmness and microstructure of water-in-oil spreads (60% fat) produced using 0.25% κ-carrageenan. Increasing levels of zinc from 0 to 15 mM caused a significant reduction in the apparent viscosity of the aqueous phase from 10.9 to 7 mPa s at 60 °C but resulted in an increase in the storage modulus (from 2.5 to 17688 Pa) and the gelling temperature (from 11.2 to 31.1 °C) on cooling to 6 °C. The firmness and storage moduli of water-in-oil spreads was significantly increased with increasing zinc addition up to levels of 1.5 mM zinc. At higher levels of zinc addition, the firmness and storage moduli of the water-in-oil spreads were significantly reduced compared to the control. The microstructure of water-in-oil spreads containing zinc was similar to the control in terms of droplet size of the aqueous phase (1–9 μm). Results indicated that fortification with zinc altered the rheology and firmness of κ-carrageenan-based water-in-oil spreads.

Keywords: κ-Carrageenan, Rheology, Water-in-oil spreads, Zinc fortiWcation