Microstructure and chemical composition of camel and cow milk powders’ surface

Abstract

This study aimed at investigating the chemical composition and microstructure of spray dried camel and cow milk powders' surfaces with two different milk-fat contents (1 and 20g 100 g −1). The SEM (Scanning Electron Microscopy) micrographs showed that spherical particles with a 'brain'-type surface for both milk powders were produced. The surface roughness (Ra) of whole (WDMP) and skimmed (SDMP) camel milk powders (Ra = 7.6 ± 0.4 nm and 5.6 ± 0.7 nm, respectively) were significantly lower as compared with the partially skimmed (PSCMP) and skimmed (SCMP) cow milk powders. The XPS (X-ray Photoelectron Spectroscopy) analysis highlighted that the surface of skimmed camel milk powders contained twice the lactose amount (17.7 ± 0.8%) as compared to cow milk powders (8.7 ± 0.4%). Furthermore, both milk powders showed the overexposure of proteins and fats at their surfaces regardless of the fat content. The CLSM (Confocal Laser Scattering Microscopy) micrographs highlighted that most of the camel milk fat globules were encapsulated by the proteins near the powder surface. Camel milk fat behavior during particle formation was attributed to their lower size distribution and their higher crystallization temperature.

Physicochemical, techno‐functional, and fat melting properties of spray‐dried camel and bovine milk powders

“…Similar observations were reported by Zouari, Schuck et al. (2020). The latter indicated that camel milk fat was homogeneously distributed in the camel milk powder showing higher encapsulation degree.…”

“…This observation indicated that the fat did not interact with water during water activity measurement. Actually, it was demonstrated that fats were considered as nonreacting component with water and had no influence on the water activity of milk powders (Jouppila, Kansikas, & Roos, 1997; Zouari, Schuck et al., 2020). In addition, Schuck et al.…”

“…The latter indicated that camel milk fat was homogeneously distributed in the camel milk powder showing higher encapsulation degree. This was linked to the smaller mean diameter of camel milk fat globules compared to bovine milk fat globules (Karray, Lopez, Ollivon, & Attia, 2005) and the higher mechanical resistance to disruption of camel milk fat globules as compared to those of bovine ones (Zouari, Schuck et al., 2020). These milk fat globule characteristics limited the free fat exposure to the camel milk powder surface.…”

“…It is important to note that the dispersibility of whole‐fat camel and bovine milk powders decreased drastically as compared to the skimmed ones (Table 2). This could be linked to the exposed fat at the powder particle surface, which could limit the powder dispersibility in water (Zouari, Schuck et al., 2020).…”

“…Recent studies on camel milk powder have been focused on its particle structure and surface composition (Zouari, Schuck et al., 2020), as well as its behavior during drying (Habtegebriel, Edward, Wawire, Sila, & Seifu, 2018; Zouari et al., 2019; Zouari, Mtibaa et al., 2020) and its physicochemical changes upon storage (Ho et al., 2019; Zouari, Briard‐Bion et al., 2020). However, none of these explained the practical conditions to use skimmed or whole‐fat camel milk powder in future applications.…”