In-Situ Production of Modified Starch and Pickering Emulsions by Planetary Ball Milling

Abstract

Rice starches with different degrees of modification are obtained by high impact-milling and evaluated as stabilizers of oil/water (O/W) Pickering emulsions. The objective is to produce in-situ Pickering emulsions in a planetary ball mill (PBM), analyzing the effect of starch milling time (10, 40, 70 min) and starch concentration (3%, 9%, 15%, 21%, 27%) on emulsion attributes such as droplet size (D50, D[4,3]), oil retention (OR) capacity, creaming percentage (C), and stability time (ST). The traditional homogenization method using a rotor-stator device is adopted as a reference. By homogenization in PBM, good quality emulsions (droplet size lower than 50 µm and 18 days stable period) are obtained by using 15% of rice starch milled during 40 min. In contrast, the emulsion cannot be obtained by traditional homogenization for the same process conditions. However, with 70 min of PBM and 21%–27% of starch content, a long-term ST (60 days) is achieved by means of both homogenization methods. These optimal emulsions show a low droplet size (D50 ∼ 10 µm) and a great affinity of the milled starch toward the interface in optical microscopy images, which explains the significant contribution of starch particles aimed at controlling the droplet coalescence.