Principles and applications of spectroscopic techniques for evaluating food protein conformational changes: A review

Proteins are essential nutrients required in various body functions and normal human life. However, in the food industry, the application of proteins especially those of plant origin have been limited due to their poor functionality. Although nowadays, diverse modification techniques are usually employed to improve their performance in food products, it is also important that effective methods for monitoring the resultant conformational changes induced during protein modification are developed. In this review, the relationship between protein conformation and functionality is briefly discussed. Thereafter, the underlying principles behind five selected spectroscopic techniques i.e. Fourier transform infrared, Raman, circular dichroism, fluorescence, and ultraviolet spectroscopies are introduced and their recent applications for monitoring conformational changes that occur during physical, chemical or enzymatic modification of proteins are addressed. In addition, the advantages and limitations of each spectroscopic technique are comparatively discussed and perspectives on the current situation alongside future trends are highlighted. Spectroscopic techniques present an attractive panacea for evaluation of conformational changes during protein modification. Although certain challenges especially with complex food materials require urgent attention thus, more robust spectroscopic solutions should be exploited in the future.