Microstructural design of food gels to control material properties and release of nutrients

Kanyuck, Kelsey Michele ORCID: 0000-0002-6779-2626 (2021). Microstructural design of food gels to control material properties and release of nutrients. University of Birmingham. Ph.D.

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Abstract

Hydrocolloid systems can be used to tailor sugar release to match the needs of specific populations such as diabetics and athletes. A chewable gel with controllable release of sugars is of interest to food manufacturers, but first a fundamental understanding of the impacts of hydrocolloid structure on texture and release must be developed. Literature has shown a strong relationship between the structure and function of hydrocolloids and demonstrated the ability to optimise properties through control of the microstructure. The structure and gelation of maltodextrin (MD) and high acyl (HA) gellan gum have been established in previous research and were built upon to understand this more complex system.

The microstructure of MD gels and mixed gels with HA gellan gum were examined using techniques such as differential scanning calorimetry, large deformation gel fracture, Young’s Modulus, and microscopy. Lower holding temperatures (5 °C compare to 45 °C and 60 °C) increased the enthalpy of MD gels which resulted in a more brittle gel with a higher modulus. The microstructure of these gels was more heterogeneous with larger pockets of water and smaller but an increased number of crystallites. The work suggested that concentration and temperature effected the helix-coil transition of maltodextrin and the subsequent formation of the aggregate network. An interpenetrating network (IPN) was observed between mixed gels MD and HA gellan which ranged in texture from hard and brittle to easily deformable based on the relative amounts of each polymer and the subsequent changes in microstructure. Aggregation of MD occurred within the pores of the HA gellan gum network which added brittleness and an increased modulus to the composite gel. Determining the type of network allowed prediction of the behaviour using characteristics of the existing model.

Compared to smaller molecular weight carbohydrates (such as glucose and maltose), MD was slower to be released from the gel and required the digestive enzyme amylase for breakdown into smaller units. In comparison with other hydrocolloid gels, an IPN with MD resulted in lower release than phase separated gels, and both types of mixed gels were lower than maltodextrin alone. Swelling of HA gellan gum also reduced the release of carbohydrates and the swelling was found to be driven by an osmotic imbalance. This work provides a fundamental understanding of MD and HA gellan gum gels and the ways the microstructure can be developed to select for specific textures and release profiles. Examination of the underlying principles of gelation and the methods to create specific microstructures allowed this understanding.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):