Inclusion of starch in imitation cheese: Its influence on water mobility and cheese functionality

The impact of starch type and concentration on the nature of water in and the rheology of imitation cheese were investigated. Imitation cheese (55% moisture) containing four starches (native, pre-gelatinised, resistant or waxy corn) at inclusion levels of 1.9%, 3.9%, 5.8%, 7.8%, or 9.9% w/w were manufactured using a Brabender Farinograph-E®. The textural properties were assessed by torsion gelometry and dynamic rheology and the mobility of water by nuclear magnetic resonance (NMR) relaxation techniques. Cheese microstructure was assessed using light microscopy. Increasing the starch content changed the texture of cheeses from ‘soft’ to ‘brittle/tough’ and significantly (p<0.05) decreased the mobility of water. Cheese melt and hardness were influenced by the mobility of water. Matrices in which the water was more mobile produced good melting soft cheeses, while cheeses in which water was less mobile were tough and non-melting. Light micrographs showed that starch type influenced cheese microstructure. The native and pre-gelatinised starches became swollen and disrupted the continuity of the protein matrix, separating the matrix into a protein and starch phase. Resistant and waxy corn starches were present in the protein matrix as small discrete particles, appearing relatively intact, unswollen and relatively unchanged by the cheese manufacturing process. The study indicates that varying the level/type of starch alters the water mobility and thus the functionality of imitation cheeses.