Moreau, Lydie
(2009)
Impact of sodium chloride on breakfast cereal products.
PhD thesis, University of Nottingham.
Abstract
To reduce the amount of sodium chloride in breakfast cereals without changing their properties, it is necessary to understand the role of this salt. Hence, a model system was developed. This model, composed of native waxy maize starch, glucose and a mixture of amino-acids generated similar colour and residual volatiles after heating compared to commercial breakfast cereals. Systematically designed experiments used this model to study the influence of NaCl concentration (0 % to 5.44 %) on colour, residual volatiles and acrylamide formation. It was found that higher NaCl concentration led to darker products (p<0.05) and significantly decreased acrylamide formation in the model systems. However, it did not have a significant impact on residual volatile levels. These findings were confirmed by observations made on wheat, wheat and rice mixture, com and rice commercial cereals.
The impact of NaCl on colour and acrylamide formation indicated that this salt might influence Maillard and/or caramelisation rates and pathways. As NaCl is a plasticiser, it can allow the rubbery state to be maintained for a longer period during heating, improving reactants' mobility and Maillard reactions. However, it was found using the model systems mixed with several types of plasticisers (NaCl, KCl or trehalose), that the NaCl plasticising effect was not the major influence. The models also demonstrated that the hygroscopic behaviour of NaCl was not linked to its impact on colour and acrylamide formation.
In investigating salt's influence on starch, native waxy maize, cassava or potato starch were mixed with NaCl (0 to 4 %; moisture adjusted to 20 %) and were heated at 230°C for 45 min. Microscopic observations, wide angle X-ray, viscosity, intrinsic viscosity and DSC data all suggested that starch was degraded by the heat treatment, and NaCl accelerated starch break down into smaller molecules, i.e. glucose. The glucose potentially formed could then caramelise, which might explain the NaCl impact on colour formation in model systems and breakfast cereals. Among other tested salts, CaCl[subscript]2 and MgC1[subscript]2 also enhanced starch degradation during a heat treatment.
In studying glucose solutions containing salt (NaCl, CaCl[subscript]2 or MgCl[subscript]2) and heated between 180 and 230 °C, it was observed that salt enhanced colour formation via caramelisation (p<0.05). Mixtures of glucose, amino-acids and salt (NaCl, CaCl[susbscript] or MgCl[subscript]2), heated under the same conditions, showed that salt significantly decreased colour formation (p<0.05), which was most likely generated via Maillard reactions. Hence, salts could slow down Maillard reactions, explaining why lower acrylamide contents were found in model systems and cereal products when NaCl was present.
As NaCl seems to influence Maillard and caramelisation reactions, decreasing or removing NaCl from breakfast cereal recipes might not only alter the salty taste but also the overall flavour. CaCl[subscript]2 and MgCl[subscript]2 seemed to have similar or even more impact on colour formation compared to NaCl. Adding these salts to breakfast cereal products with a low NaCl content was found to compensate for the colour loss. Adding CaCl[subscript]2 or MgCl[subscript]2 also improved the overall flavour of breakfast cereals, even though it did not compensate entirely for the taste loss.
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