# Applications of Mueller Matrix Polarimetry to Biological and Agricultural Diagnostics: A Review
## 4 Applications of MMP to Biology and Agriculture
### Studying the Structure of Organic Materials  
MMP can be a useful tool for studying various materials in order to assess the quality of products made from them and, subsequently, detect defects. An experimental procedure using MMP, which enables studying foams, was described in [117]. The use of MM spectroscopic ellipsometry to study the anisotropy of materials, in particular, polyethyleneerephthalate (PET) was proposed in [94]; this method proved to be successful in obtaining additional information about the anisotropy of materials. MMP was used to study films of chiral nanocrystalline cellulose [95] and to measure the anisotropy and orientation of liquid crystals [107]. Strain-induced birefringence shows linear relationships with both strain and orientation of chain segments. MM scatterometry was used to compare the polarization properties of white fabric and white wood [108]. Linear and circular birefringence, as well as circular dichroism in chiral nanocellulose films obtained by self-assembly of cellulose nanocrystals, were estimated using MMP [109]. Optical chirality parameters were determined from MM measured for organic materials such as sugar solutions and liquid crystals [12]. The MM-based measurement of the intensity difference between right and left circular polarizations in light scattered from an optically active medium is sensitive to the molecular conformation of complex biopolymers [63].  
MMP can be used to quantify the anisotropy of plant fibers by the MM differential decomposition [110]. Measuring the topology of polymer fiber scaffolds by MMP is of considerable interest for tissue engineering [111]. It has been shown that the MM responds to the orientation of the fibers and their mechanical properties, which confirms the accuracy of the MMP method is sufficient for evaluating fiber structures.  
Tomographic Mueller scatterometry (TMS) can visualize the topology of structures down to tens of nanometers in size, which is promising for non-destructive testing in nano-manufacturing [83].  
IR laser spectroellipspometry [76] and polarimetric FTIR spectroscopy [97; 98; 99; 100] aiming to measure the Mueller matrix of liquid and solid organic materials would be suitable, in particular, for complex analysis of folders to determine fat, protein, fiber, ash or grain gluten content.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Sample Type** & **Methods** & **Sample Properties** & **References** \\ \hline \multirow{4}{*}{Tissues} & MM-OCT and & Optical polarization properties, & [20; 32; 33; 34] \\  & MM-OCT and & microstructural characteristics, & [27; 54] \\  & MM imaging polarimetry, & cell properties, & [56; 68] \\  & MM fluorometry & pathology detection, & [24; 25; 28; 29; 30; 50; 114] \\  & & microbial contamination & [26] \\ \hline \multirow{2}{*}{Milk} & \multirow{2}{*}{MM scatterometry} & Size distribution, & \\  & & fat and protein content & \\ \hline \multirow{2}{*}{Vegetable oils} & \multirow{2}{*}{Transmission MMP} & Optical polarization properties, & \\  & & authenticity & [40; 41] \\ \hline \multirow{2}{*}{Meat} & MM imaging polarimetry & Freshness assessment & [42] \\ \hline \multirow{2}{*}{Plants} & MM spectopolarimetry & Chlorophyll organization & [43] \\  & Microwave MMP & Vegetation & [70; 115; 116] \\ \hline \multirow{2}{*}{Soils} & MM scatterometry & Particle size and optical properties & [46] \\  & Microwave MMP & Moisture content, surface roughness & [45] \\ \hline \end{tabular}
\end{table}
Table 1: _Cont._MMP is very important in studying protein systems. For example, the fractal structure of protein aggregates can be determined from the light scattering matrix [81]. Additionally, fluorescence polarization measurements [91], especially in the form of the Mueller matrix [92], provide information on molecular orientation and mobility and the processes that modulate them, including receptor-ligand interactions, protein-protein and protein-nucleic acid interactions, proteolysis and fluidity membranes [118].