Rheological properties of mashed potatoes made from dehydrated flakes: effect of ingredients and freezing

The rheological behaviour of mashed potatoes made from dehydrated potato flakes was studied using helical ribbon geometry, which enabled changes in the dynamic mechanical properties, as a function of ingredients concentration, to be followed. Mashed potatoes were also frozen in order to determine the changes that occurred in the cell structure. Response surface analysis was used to establish the empirical models for expressing the effects of significant ingredients on rheological properties. Results showed that both dynamic moduli (G', and G") were significantly influenced by potato flake concentration (alpha< 0.01) and the butter concentration (alpha<0.05 for G' and a<0.10 for G"), while the salt concentration had a significant quadratic effect (alpha< 0.05) on the storage modulus (G'). Significant interactions occurred between potato flakes and milk concentrations, and potato flakes and salt concentrations, and these were detected by the dynamic moduli. Breakdown of the cell wall by freezing decreased G', G" and eta* values, showing that the frozen/thawed mashed potatoes consisted of dilute dispersions of swollen and disrupted intracellular starch granules.