THE USE OF NEAR-INFRARED SPECTROSCOPY TO DETECT CHANGES IN THE FORM OF AMORPHOUS AND CRYSTALLINE LACTOSE

The suitability of near infra-red spectroscopy (NIR) to follow changes in both the amorphous and crystalline state of lactose at room temper ature was investigated. Amorphous lactose samples were stored in seale d glass jars with saturated salt solutions to control the relative hum idity. NIR spectra were recorded after various periods of storage and the data related to calorimetric and thermo-gravimetric assessments of the physical form of the material. Differentiation between crystallin e and amorphous states of lactose was found possible by studying the s hape and magnitude of regions of the near infra-red spectrum correspon ding to combination and first over-tone stretching frequencies of wate r. It was possible to follow changes in the amorphous, the onset of cr ystallisation and the solid state transition from beta- to alpha-lacto se. NIR with benefits of being non-invasive: non-destructive and opera ting at room temperature, has been shown to be a valuable tool with wh ich to assess changes in the physical form of lactose. (C) 1998 Elsevi er Science B.V. All rights reserved.