A simple, organic solvent-free media-milling process was applied to modify the structure and morphology of maize starch granules. During the milling process, the sizes of starch granules reduced dramatically while their crystalline structure was largely damaged as verified by differential scanning calorimetry and X-ray diffraction. The surface hydrophobicity of milled starch was also characterized by contact angle measurement. These media-milled starch suspensions with different starch concentrations (i.e., 2.4%, 7.2% and 10.0%) were used as stabilizers to form Pickering emulsions. The droplet sizes of the Pickering emulsions prepared in this study ranged from approximately 10μm to 900μm depending on the milling time and the initial starch concentration. The droplet sizes decreased with prolonged milling time and increased initial starch concentration. Milled starch particles of around 100nm anchored at the emulsion interfaces were observed by cryo-scanning electron microscopy. Although some emulsions creamed immediately after homogenization, most emulsions exhibited stability against coalescence during the long-term storage of 6months. The emulsions also exhibited benign stability against a wide range of pH, ionic strength and temperature conditions. This research provides a new green approach to form food-grade emulsions to deliver active food ingredients.
Keywords: Media-milling process; Pickering emulsions; Starch granules.
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