Real‐time measurement of heat stability of skim milk using attenuated total reflectance (ATR)‐FTIR spectroscopy.

Milk proteins are susceptible to denaturation and aggregation upon heating, affecting product quality and shelf‐life. Understanding the underlying molecular changes during heating is important to the dairy industry for process optimisation and product functionality. This study used Attenuated Total Reflectance (ATR)‐Fourier Transform Infrared (FTIR) spectroscopy to non‐destructively measure changes in protein molecular structure as the precursor to heat‐induced aggregation in milk. Raw skim milk was divided into three subsamples, adjusted to pH 6.2, native pH or pH 7. Each sample was heated at 85°C on a BioATR crystal, with scans taken at 1‐min intervals over 20 min using FTIR to measure protein denaturation and aggregation. The second derivative of the amide I region was used to measure changes in protein structure, with the spectra for pH 6.2 samples changing faster than pH 6.8 or pH 7 samples, indicating a higher rate of denaturation. The peak at 1072 cm−1 related to colloidal calcium phosphate (CCP) increased with increasing temperature and pH. More extensive changes in CCP between colloidal and serum phases and protein denaturation/aggregation correlated with lower heat stability in milk. This study highlights the potential of ATR‐FTIR spectroscopy for assessing the heat stability of milk via in situ measurement of changes in protein structure and CCP. [ABSTRACT FROM AUTHOR]