A rheological study on the application of carbohydrate-protein incompatibility to the development of low fat commercial spreads

Abstract

The small and large deformation properties of commercial low fat spreads and traditional full fat products have been investigated in order to develop a background understanding of the changes in viscoelastic properties and the structural organisation occurring as a result of addition of biopolymers to the aqueous phase of low fat dispersions. Parameters have been derived from compression analysis, dynamic oscillation (frequency, strain and temperature sweeps) and creep compliance testing. It seems that the direct replacement of fat with a biopolymer-structured aqueous phase does not imitate the plastic rheology of butter and margarine. Thus, the ratio of plastic to maximum stress ( σ p σ m ) of butter and margarine is substantially higher (0.96–1.0) than the ratio of inflectional to maximum stress ( σ i σ m ) of commercial low fat spreads with a strong, gel-like character (up to 0.83). Additionally, some commercial embodiments with reduced amounts of structural components have stress-strain profiles resembling those of viscous solutions instead of a plastic product. Dynamic oscillatory measurements have characterised the mechanical properties of water-continuous low fat spreads. Dispersions reproduced the mechanical profile of three-dimensional biopolymer gels with a high elastic component (tan δ ≈ 0.04) and a substantial linear response to increasing amplitude of oscillation (up to 10% deformation). Products comprising hydrolysed starch as one of the functional ingredients show long melting profiles upon heating, which contrast strongly with the ‘melt in the mouth’ properties of butter. In accordance with the above, butter requires lower initial strain to exhibit negligible recovery of shape after the removal of stress, than do commercial low fat spreads with a pronounced elastic element, during a creep compliance experiment.