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

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.