Water Mobility and Crystallization Action of Lactose-water Systems by Oxygen-17 and Carbon-13 NMR

Systems ranging in concentration from 10-60g lactose/100g water were investigated by fully proton decoupled ¹⁷O and fully proton decoupled ¹³C Nuclear Magnetic Resonance (NMR). The relation between ¹⁷O NMR transverse relaxation rate measurements and lactose concentration showed water mobility decreased linearly with increasing lactose concentration up to 25g lactose/100g water and decreased rapidly and nonlinearly above that level. Water mobility was used to monitor lactose crystallization in supersaturated solutions with time. The 13 C NMR showed no significant differences in chemical shifts of carbon atom peaks in lactose molecules during crystallization. However, depending on the method of sample preparation, mutarotation could be observed.