This work demonstrates the properties of calcium-fortified potato starch prepared by immersion in natural mineral water containing an extremely high level of calcium (468 ppm) and its food application. The calcium content of the fortified potato starch produced by use of the original mineral water was as high as 813 ppm, while calcium content of the control potato starch was 99 ppm. Rapid visco-analyzer data revealed that the calcium-fortified potato starch had a markedly lower peak viscosity and breakdown and a higher peak viscosity temperature than the control potato starch. Furthermore, calcium fortification caused a significant decrease in starch swelling power. Pound cakes made from the calcium-fortified potato starch and wheat flour blends tended to have a higher specific volume and sensory score of appearance than those made from the control potato starch and wheat flour blends. These findings suggest that the use of calcium-fortified potato starch is critical for making pound cakes with good quality in appearance.

Water sorption isotherms and effective moisture diffusivities were determined at 20 degrees C for sponge cakes at high water activity as a function of their initial porosity, in the range 86 and 52% (0 g/g dry basis fat content), and of their fat content, ranging between 0 and 0.30 g/g dry basis (67% initial porosity). The equilibrium moisture values were not affected by food structure and decreased with increasing fat content. The effective moisture diffusivity decreased from 7.5 to 0.3 X 10(-10) m2/s with increasing moisture content from 0.30 to 2.20 g/g dry basis. Decreasing initial porosity from 86 to 52% decreased effective moisture diffusivity by more than four orders of magnitude. This behaviour was related to differences of water transfer mechanisms, with the contribution from liquid water diffusion in the solid matrix and from vapour water diffusion in pores. Increasing fat content of 0.30 g/g dry basis in sponge cake, independently of porosity, decreased effective moisture diffusivity by more than five orders of magnitude. A predictive mathematical model was used to simulate moisture intake in two-composite food systems: sponge cakes with varying initial porosities and fat contents and an agar gel as a model of a non-rate limiting water source. Increasing the density of the structure or addition of fat in the cereal-based phase could increase shelf life of composite foods.