The Applicability of near Infrared Reflectance Spectroscopy for Determining Solubility and Digestibility of Heated Protein under High Pressure

Abstract
The potential of near infrared (NIR) reflectance spectroscopy for non-destructively probing structural changes in protein during the process of denaturation was investigated. Lysozyme as a model protein was adjusted to 15% moisture content, placed in a steel cylinder and then heated at 30, 90, 120 and 150°C under pressure conditions of 10, 15, 30 and 45 MPa. Significant changes were observed in absorption bands near 2144, 2168 and 2208 nm with increases in temperature and pressure. The spectral changes were, in general, much larger for samples subjected to both high temperature and pressure than for those subjected to high temperature only. It is likely that these changes are due to changes in the secondary structure of protein. Absorbance changes at the above wavelengths showed high correlations to variations in solubility and digestibility of protein treated under high heat and pressure conditions. The results of multiple linear regression analysis suggest that NIR spectroscopy may be used to predict the solubility and digestibility of protein.