Use of FTIR to study secondary structure of texturized plant proteins by high moisture extrusion cooking, a comprehensive review.

Fourier-Transform Infrared spectroscopy (FTIR) is often used by researchers to understand the texturization mechanisms of plant proteins. High Moisture Extrusion-Cooking (HMEC) is the main process used for their texturization by heating, mechanical shearing, and subsequent cooling of a high-moisture mixture, which causes denaturation and restructuration of proteins, resulting in an anisotropic product, commonly called "meat analog". Researchers try to link the properties of extrudates to the secondary conformation of proteins, which are supposed to aggregate and align in the flow direction within the die. This review will attempt to show the reasons for studying the secondary structures of plant proteins in HMEC-textured products, and compare and discuss the different methods applied to prepare samples and analyze them by FTIR. A focus will be put on the different methods of spectra analysis (i.e., peak deconvolution, and reference tables used), for which a total of around 60 scientific papers have been carefully analyzed to illustrate the disparity of reference tables used in the literature. A discussion will summarize the various hypotheses currently found in the literature, and provided by FTIR to explain the texturization mechanisms of plant proteins through HMEC. Finally, advice such as comparing results with other amide bands and other analysis methods and following published procedures, are provided as an outlook for future improvements in FTIR data quality, processing and interpretation.