Crystallization Properties and Polymorphism of Triacylglycerols in Goat’s Milk Fat Globules

• Published in: Journal of agricultural and food chemistry 2008-06, Vol.56 (12), p.4511-4522
• Main Authors: Ben Amara-Dali, Wafa, Lopez, Christelle, Lesieur, Pierre, Ollivon, Michel
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Calorimetry, Differential Scanning; Chemical Changes Induced by Processing/Storage; Chemical Phenomena; chemical structure; Chemistry, Physical; Cold Temperature; cooling; Crystallization; differential scanning calorimetry; Emulsion; Emulsions - chemistry; fat globules; fatty acid composition; Female; Food engineering; Food industries; Fundamental and applied biological sciences. Psychology; Glycolipids - chemistry; Glycoproteins - chemistry; goat milk; Goats; Hot Temperature; Life Sciences; melting; Milk and cheese industries. Ice creams; milk fat; rheological properties; Sensitivity and Specificity; Synchrotrons; temperature; triacylglycerols; triglycerides; Triglycerides - chemistry; X-Ray Diffraction
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf073491g

The sensorial, functional, and nutritional properties of goat dairy products result from the specific fatty acid composition of goat’s milk fat. However, information on the physical and thermal properties of goat’s milk fat is scarce. In this study, crystallization of triacylglycerols (TG) in goat’s milk fat globules was investigated using polarized light microscopy and the coupling of time-resolved synchrotron radiation X-ray diffraction (XRD) and high-sensitivity differential scanning calorimetry (DSC). The molecular organization of the solid fat phase was characterized for cooling rates between 3 and 0.1 °C/min. Quenching of goat’s milk fat globules from 50 to −8 °C and 4 °C was also examined to identify the most unstable polymorphic forms of TG. Then, the melting behavior of fat crystals was studied on subsequent heating at 1 °C/min. Triple chain length (3L: 68.6−70 Å) and double chain length (2L: 37−45.4 Å) structures were characterized and 5 polymorphic forms, α, sub-α, β′1, β′2, and β were identified. Polymorphic transitions were observed within goat’s milk fat globules as a function of time after quenching and as a function of temperature on heating. From a technological point of view, this work will contribute to a better understanding of the rheological properties as well as on the flavor evolutions of goat’s milk-based products.