Thermal characteristics of crystalline and amorphous 2′-fucosyllactose, a human milk oligosaccharide

Abstract

The thermal characteristics of crystalline and amorphous forms of a human milk oligosaccharide, 2ʹ-fucosyllactose (2ʹ-FL), were investigated by differential scanning calorimetry and thermogravimetric analysis, and compared with the two forms of α-lactose monohydrate. Crystalline 2ʹ-FL (87.48% crystallinity according to X-ray diffraction) showed dehydration at 143.4 °C (close to lactose) and melting at 230.6 °C (the same as β-lactose crystal). Amorphous 2ʹ-FL showed glass transition at 127.6 °C and crystallisation at 192.8 °C, which were much higher than the corresponding temperatures for amorphous lactose. 2ʹ-FL showed thermal decomposition at temperatures about 10 °C higher (210–212 °C) than lactose, indicating the higher thermal stability of 2ʹ-FL. Amorphous 2ʹ-FL showed sharp decreases in glass transition (127.6 °C to 36.5 °C) and crystallisation (192.8 °C to 103.4 °C) temperatures with increasing water activity (aw) from 0 to 0.53, above which no glass transition or crystallisation was observed.