DEVELOPMENT OF A TIME DOMAIN (TD) NMR APPROACH BY USING THE RELATION BETWEEN MOLECULAR MOBILITY AND CRYSTALLIZATION BEHAVIOR TO QUANTIFY CAKING IN FOOD POWDERS

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2022-12-19

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Güner, Selen

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Caking is one of the most important factors affecting fluidity and quality of powdered food samples by distorting the stability and functionality. Time-Domain Nuclear Magnetic Resonance (TD-NMR) techniques are frequently used in the polymer, drug and food industries since they require no initial sample preparation before the measurement and provide rapid results. The main goal of the study is to quantify crystallinity by using TD-NMR, Solid Echo (SE) and Magic Sandwich Echo (MSE) sequences. The method was first applied for the control and freeze dried sugar samples (glucose, sucrose and lactose) in powder form, and high correlation (>0.96) was found with the X-ray diffraction (XRD) and MSE crystallinity. In the second part, crystal growth in highly saturated sugar solutions were studied for glucose, fructose, allulose, lactose and sucrose equilibrated to 28°C from 50°C. Fitted kinetic model suggested that the crystallization rate was slowest for glucose and fructose, following allulose, lactose, and sucrose, respectively. In the last part, confirmed quantification method was applied to cheese and milk powders stored at different relative humidities (40, 50, 60, and 70%) and their crystallinities were related to caking tendency and fat content of the powders. Surface and total fat content, moisture content, water activity analyses were also conducted complementary to NMR analyses. As a consequence of the study, it was found that molecular mobility could be modelled to calculate crystallinity by TD-NMR techniques, which gives information on physical changes such as crystal growth and caking tendency. The method could be a user friendly alternative to XRD.

Subject Keywords

NMR, Caking, Crystallinity, Fat Content, Moisture Adsorption

URI

https://hdl.handle.net/11511/101333

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

S. Güner, “DEVELOPMENT OF A TIME DOMAIN (TD) NMR APPROACH BY USING THE RELATION BETWEEN MOLECULAR MOBILITY AND CRYSTALLIZATION BEHAVIOR TO QUANTIFY CAKING IN FOOD POWDERS,” Ph.D. - Doctoral Program, Middle East Technical University, 2022.