A reverse engineering approach to sucrose replacement in biscuits: modelling texture

The global rise in chronic non-communicable diseases such as obesity, type 2 diabetes, and coronary disease has been linked to high intake of sugar and excessive energy consumption. The main dietary source of added sugars in UK are soft drinks, bakery and confectionery products. Biscuits, with around 30-40% sugar content, are versatile products and popular among all consumer groups, particularly children. Owning to concern over increasing childhood obesity rates and with the aim to help people follow a healthier lifestyle a UK Government policy has come into force1 restricting the location and in-store promotion of high fat, sugar, and salt products (HSFF). This has driven further efforts from the food industry in product reformulation. However, the replacement of sucrose with healthier alternatives in bakery products such as biscuits has been proven challenging due to the multifunctional role that sucrose plays, in addition to providing sweetness2.
During the last decades research has focused on testing ingredients as sugar replacers (polyols, oligofructose and inulin, maltodextrins, polydextrose,etc) and assessing the effect on biscuit quality. Recently a new theory on how sucrose, water and biopolymers (gluten and starch) interact thermodynamically in dough and biscuit systems has been proposed defining the plasticising and hygroscopic properties; the main parameters that determine physical and sensorial textural properties of biscuits3. Sucrose gets solubilised during mixing and baking, then a supersaturated solution (rubbery state) is formed during baking and finally sucrose may recrystallise during cooling and storage4. Sugar concentration during baking also impacts amylopectin glass transition temperature and starch gelatinisation process. Therefore, a further understanding on the factors and parameters that define carbohydrate transitions (melting, recrystallisation, gelatinisation) during processing of biscuits is needed for the development of a holistic picture of the thermodynamic changes in the biscuit systema and how these define the physical and sensorial textural properties of biscuits.
The hypothesis of this study is that thermodynamic and kinetic changes in a biscuit system (sugar-water-biopolymer) that happen during processing could be modelled to design novel sucrose replacers and reformulation strategies to decrease sucrose while achieving targeted textural properties.
The research objectives are:
1)To evaluate the thermodynamical processes (glass transition and crystallisation phenomena) and kinetic changes (water diffusion) during mixing, baking and storage of biscuits made with sucrose or sucrose replacers (polyols, rare sugars, other carbohydrates) (Modulated Differential Scanning Calorimetry, low field NMR)
2)To characterise the evolution of the structures from initial mixing to final product from molecular to micron length scales using ultra small angle X-ray scattering (USAXS) and diffraction.
3)To assess physical properties of dough and biscuits samples (rheometer, texture analyser, dimensions, X-ray tomography).
4)To analyse the sensory perception of biscuits mouthfeel (oral processing and descriptive qualitative methods) and sweetness (in vitro and in vivo sugar diffusion). Correlations between perception and instrumental results will be assessed.
5)To use both quantum chemical models and classical molecular dynamics to calculate physical and phase properties of sucrose replacers at the single molecule, small to medium cluster and bulk levels.
6) To create a Quantitative Structure Activity Relationships (QSARs) by correlating sucrose replacers' properties (objective 1), texture phase space (objective 2) and textural descriptors (objective3 & 4), and). The QSAR models will be developed and tested to predict biscuit physical and sensorial textural properties.