Chemical infrared imaging of protein, carbohydrates and fat in agri-food mixtures

3 Chemical infrared imaging of protein, carbohydrates and fat in agri-food mixtures 

Infrared imaging can be used for the non-destructive, spatially resolved determination of protein, carbohydrate, and fat in a mixture. The corresponding infrared images are often referred to as chemical images. Chemical imaging is extremely useful in agri-food studies for determining the spatial distribution of protein, carbohydrates, fat and water mixtures, and because of its importance, this subject will be addressed in some detail. 

In Fig. 12.2 ATR infrared spectra of starch (a complex carbohydrate) (A) soy protein (B), canola oil (mostly triglycerides) (C), and a 1 1 1 mathematical mixture of the three (D) are presented. The regions containing diagnostic bands appropriate for infrared imaging are identified with dashed boxes. Note how easily all three components may be identified in the mixture spectrum (D). 

Since the v(OII) for carbohydrates is complicated by overlapping u(NII) bands from protein and the i (OH) band from water, large bands in the C-O stretch region between 1250 cm-1 and -900 cm-1 are usually chosen for functional group mapping. The iTCIF) and WCH3) bands for fats and oils overlap HOF) and 

An embedding and polishing method can be used as an alternative to microtoming.48 In this case, a sample is placed in an uncured polymer resin, cured 

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