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Bakhai, Bijol (2022) Temperature-dependent study of gelling biopolymers using infrared spectroscopy. PhD thesis, University of Nottingham.

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Abstract

This Thesis is centred around understanding conformational changes that occur within biopolymers which have major implications in food industry. Monitoring the continuous conformational changes of biopolymers subjected to temperature changes presents a challenge. Infrared spectroscopy is a powerful spectroscopic technique that can measure structural changes quantitatively. This Thesis focuses on probing the temperature-variable changes of gelling biopolymers, using Fourier transform infrared (FTIR) spectrometer coupled with a modified attenuated total reflectance (ATR) accessory, to determine the conformation and dynamics of the system. The modified system allowed for continuous collection of spectral data (stable to 0.01 °C), with precise control and variation of the sample over a temperature range of -15 °C to +80 °C.

Two food additives, namely locust bean gum (LBG) and carrageenan, have been specifically studied in this Thesis. Both of these are naturally occurring polysaccharides extracted from the endosperm of carob seeds (Ceratonia siliqua) and red seaweed (Rhodophyceae), respectively. Although they differ significantly in chemical structure and side-chain functional groups, both have similar properties and exhibit thickening, gelling and stabilising effects that are of industrial interest. They are most used in the food industry and are of appeal in the production of frozen dairy products such as ice cream, as the addition of such high molecular weight stabilisers have been reported to reduce the unfavourable rate at which ice crystals grow during storage. This phenomenon causes the perception of coarse ‘icy’ texture and is an ongoing problem in the manufacturing of ice cream. Two of the major components that form the composition of ice cream include water and milk solids. Therefore, κ-, ι-carrageenan (gelling forms), and LBG were studied individually in water during cooling and freezing. Studies with milk powder at 5% and 10% concentrations have also been conducted with ι-carrageenan. Key changes in spectral features have made it possible to monitor the specific temperature range where the solution to gel (sol-gel) transition occurs in carrageenan, supported with multivariate analysis of data. Comparable FTIR transmission studies of carrageenan in water showed similar results but with inferior temperature resolution. The initial transformation of ι-carrageenan from random coil to helical formation appears relatively unaltered by the addition of milk powder. Hydrogel formation in LBG was difficult to ascertain spectroscopically at sub-zero temperature but showed large changes in the region associated with water/ice.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	George, Michael W.
Keywords:	biopolymers, carrageenan, locust bean gum, gelation, FTIR, food chemistry
Subjects:	Q Science > QD Chemistry > QD 71 Analytical chemistry T Technology > TP Chemical technology
Faculties/Schools:	UK Campuses > Faculty of Science > School of Chemistry
Item ID:	69513
Depositing User:	Bakhai, Bijol
Date Deposited:	03 Feb 2025 11:40
Last Modified:	03 Feb 2025 11:42
URI:	https://eprints.nottingham.ac.uk/id/eprint/69513

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