University of Nottingham, School of Biosciences in collaboration with Nestlé Product Technology Centre Confectionery, York
Background: Confectionery products are complex systems where multiple sugars coexist, typically in mixture with non-sugar compounds. Whilst concentrated sugar systems naturally evolve towards the crystalline state, the metastable amorphous state is often preferred for its superior sensorial properties. The products state is affected by their overall composition, processing history and storage conditions. It is essential to identify the critical formulation, processing, and post-processing conditions to preserve the amorphous state without increasing the amount of sugar added in the product to achieve the desired sensorial experience. This is crucial as increased sugar consumption is a well-known risk factor for chronic disease development.
Knowledge gap: Current state-diagrams describing sugar crystallisation are predominantly based on single (non-complex) component. Studies investigate the crystallisation behaviour of simple systems often with a single sugar specie, under quiescent conditions and with relatively short investigation timescale. Albeit informative, this type of studies only provides part of the required knowledge to support industrial applications, where sugars mixtures and additives are used to manufacture confectioneries implementing continuous processing equipment, and to offer insights on the typical product commercial storage times.
PhD project Aim: Understand and predict the crystallisation behaviour of concentrated sugar mixtures in chemically heterogeneous supersaturated systems.
Objectives:
1. Investigate the impact of sugar type, concentration, and the cooling induced supersaturation on the crystallisation behaviour of sugar mixes and their resulting physicochemical properties.
2. Understand the impact of non-sugar components, e.g. mouthfeel enhancers and preservatives, on sugar mixture amorphous state and re-crystallisation behaviour over time.
3. Evaluate the role of processing and post-processing conditions on the molecular assembly and amorphous state of selected formulations.
4. Evaluate the sensory response to reformulated sugar systems with a view to reduce sugar intake. This will be evaluated across different age classes.
These objectives will be met through a high throughput approach of crystallisation environment with off and online analysis evaluating particle attributes (size, number, and shape of crystals) and crystal structure (polymorph, mixed crystal systems). We will identify key predictive structural markers for self-optimisation of retarding crystallisation conditions.
Deliverables:
1. Formulate state-diagram and heat map of crystallisation conditions (incorporating representative media) in desirable formulations to prevent unwanted crystallisation. This will identify selected sugar mixtures yielding stable amorphous structures for further investigation.
2. Elucidate the impact of non-sugar crystallising compounds (inorganic salts and proteins) on the solution-to-amorphous transition and post-processing re-crystallisation of sugar mixtures and sensorial response.
3. Identify the role of manufacturing and post-processing parameters on molecular aggregation and re-arrangement upon storage.
Commercial products of interest: The mixed sugar systems investigated in this study will be concentrated flowable viscous syrup-like liquids at working temperature around 30-50°C and above their glass transition temperature (Tg).
Materials: Ingredients will be agreed with industrial partner to enable translation of laboratory knowledge into application within project scope. Sugars to be considered will cover molecular species displaying different functional groups (e.g. aldehyde vs ketone), molecular properties (e.g. molecular conformation and molecular weight), physicochemical properties (e.g. solubility and glass transition temperature) and a range of concentration ratio of co-solutes.
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