Nuclear Magnetic Resonance (NMR) study of Palm Kernel Stearin: Effects of cooling rate on crystallization behaviour

• Published in: Food science & technology Vol. 155; p. 113001
• Main Authors: Okur, Ilhami, Ozel, Baris, Ucbas, Derya, Grunin, Leonid, Sezer Okur, Purlen, Alpas, Hami, Ide, Semra, Oztop, Mecit Halil
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2022
• Subjects: 1H NMR; Crystal polymorph; Palm kernel stearin; Wide angle X-ray scattering (WAXS); X-ray scattering; 1H NMR; Crystal polymorph; X-ray scattering; Palm kernel stearin; Wide angle X-ray scattering (WAXS)
• ISSN: 0023-6438; 1096-1127
• DOI: 10.1016/j.lwt.2021.113001

In this study, effects of different cooling rates (0.5,3.3,4.7 and 6.9 °C/min) on the crystallization behavior of palm-kernel-stearin (PKS) were studied by low-field NMR relaxometry. According to results, solid fat content (SFC), longitudinal relaxation time (T1), second moment (M2) and degree of crystallinity (%) of the samples increased with increase in cooling rate from 0.5 to 6.9 °C/min. In contrast, transverse relaxation time (T2) demonstrated an opposite behavior with respect to T1 and decreased when the cooling rate increased. Additionally, effects of cooling rate on the changes of polymorph structures were detected by X-ray measurements. Degree of crystallinity showed high Pearson correlation values (α ≤ 0.05) with SFC (r= 0.771) and T1(r= 0.932). Changes in the crystal polymorphs could also be explained by NMR parameters to some extent as can be observed by the strong correlation between the β crystal content and T2 (r= 0.927). At the highest cooling rate, β′ crystals were the dominant polymorphic form and constituted 75(%) of the total crystals present. Results of this study suggested that NMR relaxometry could be used as a complementary tool to interpret the crystallization behavior of PKS. •Solid fat content, T1 and degree of crystallinity increased by increasing cooling rate.•T2 is inversely proportional to the cooling rate.•Fast cooling promotes more unstable polymorphic forms as α and β'crystals.•Solid fat content and degree of crystallinity have a strong positive correlation.•NMR parameters could be used to monitor the changes in the polymorphic forms of fats.