2.4. ATR-FTIR Measurements

FTIR absorption measurements of HM lipids were performed at room temperature using a Bruker Tensor 37 FTIR spectrometer (Ettlingen, Germany) equipped with a Bruker Optics Platinum ATR module and a liquid nitrogen cooled HgCdTe (mercury cadmium telluride) detector. IR spectra of one drop of pure HM fat were acquired in the range from 600 to 4000 cm⁻¹ with a spectral resolution of 2 cm⁻¹ in a double-sided acquisition mode. A total of 128 scans (52 s acquisition time) were averaged per spectrum, which was calculated using a Blackman-Harris 3-term apodization function and a zero-filling factor of 2. After each HM fat measurement, the ATR crystal was cleaned with Glucopon 600 CS UP solution (~50% in water, Sigma-Aldrich, Steinheim, Germany) and water to recover the initial baseline signal. In order to reduce the influence of water vapor from the atmosphere on the recorded spectra, the instrument was constantly flushed with dry air. Spectra were acquired and analyzed using the software package OPUS 8.1 (Bruker, Ettlingen, Germany).