Investigating the effect of quince seed powder on alginate hydrogels by magnetic resonance


Thesis Type: Postgraduate

Institution Of The Thesis: Middle East Technical University, Graduate School of Natural and Applied Sciences, Turkey

Approval Date: 2019

Thesis Language: English

Student: İREM ALAÇIK DEVELİOĞLU

Principal Supervisor (For Co-Supervisor Theses): Halil Mecit Öztop

Co-Supervisor: Serpil Şahin

Abstract:

Quince seed powder (QSP) and xanthan gum (XG) based oil in water emulsions were prepared with different formulations. Whey protein isolate (WPI) and sodium alginate (AL) were also combined with QSP and XG to explore possible synergistic effects. Sunflower oil was used as the dispersed phase. Emulsions were analyzed through rheology, particle size and low field 1H NMR measurements. Emulsions containing QSP or XG, WPI and AL were gelled via crosslinking with calcium (Ca2+) ions. Gels were characterized mainly by longitudinal (T1), transverse (T2) relaxation times and scanning electron microscope (SEM) images. A detailed relaxation spectrum analysis was performed to investigate the ability of different emulsion formulations on dispersing the oil phase. QSP having emulsions generally attained longer T2 values than XG samples (p < 0.05). Addition of either QSP or XG produced a more pseudoplastic flow behavior (p < 0.05). Both QSP and XG provided sufficient emulsification with different characteristics. For the hydrogels, NMR relaxometry measurements were performed using a 0.5 T system and Magnetic Resonance Imaging (MRI) experiments were performed on a 3 T system. The longest T1 and T2 results of XG emulsion gels observed at the low field agreed with the lower particle size distribution of respective XG emulsions (p < 0.05). T1 and T2 decreasing effect of oil lumps were compensated by smaller and more homogenous oil droplet distribution within the XG gels. MR images provided better insight on the relaxation times. A multi slice multi echo sequence was used and T2 relaxation maps were obtained. Relaxation decay curves showed the presence of two compartments; protons associated with the polymer matrix and protons interacting with the oil phase. Exchange between 2 compartments was also detected when the relaxation times were investigated. The contribution of 1st component was the largest in QSP hydrogels confirmed by the lowest standard deviation in the T2 maps obtained from multi echo images. This behavior was explained by the emulsification ability of QSP as also seen in the emulsions. Results showed that QSP would be a good alternative hydrocolloid that can be used in emulsion and emulsion gel formulations.