Physicochemical Characterization

Physicochemical properties of nanoencapsulation systems are important considering the stability and functional features of these systems. Food-grade nanoencapsulation systems are composed of a variety of materials including proteins, carbohydrates, and lipids. The physical properties of these materials can be changed as they undergo process stresses (e.g., temperature). For example, some of the physical changes of these materials comprising conformational changes or sol—gel transitions of proteins and carbohydrates, phase transitions of surfactants and phospholipids, glass—rubbery transitions of solid particles (McClements, 2014). Therefore, it is important to have relative information in regard to the main and common analytical methods for determining physical properties of nanoencapsulation systems.

X-ray Diffraction

Identification of a crystalline material, unit cell dimensions, and loading of food ingredients in nanoencapsulation systems can be obtained by using X-ray diffraction (XRD) (Fathi, Varshosaz, Mohebbi, & Shahidi, 2013; McClements & McClements, 2016; Neo et al., 2013). In a study conducted by Hosseini, Zandi, Rezaei, and Farahmandghavi (2013), XRD was used for providing a crystallographic structure of CS powder, CS NPs, and the oregano essential oil (OEO)-loaded CS NPs. As shown in Fig. 10.9Aa, a high pick of CS indicated a high degree of crystallinity and there is no peak in the diffrac- tograms of CS NPs, reflecting the destruction of the native CS packing structure (Fig. 10.9Ab). The presence of 1-weak peak in a diffraction spectrum of OEO-loaded CS NPs has confirmed the loading of OEO within CS NPs (Fig. 10.9Ac). In addition, they came to a conclusion that the broad peak of CS NPs may be caused by the cross-linking reaction between CS and tripolyphosphate (TPP), which may destroy the crystalline structure of CS.

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