Microwave-assisted micro-encapsulation of phase change material using zein for smart food packaging applications

Abstract: Novel zein/tet (tetradecane) and zein/tet/APC (aqueous potassium chloride) micro-encapsulated functional materials were synthesized using a microwave-assisted encapsulation technique. This technique can produce microcapsules in a very short time. In this study, we optimized the methodology used to obtain micro-encapsulation structures based on zein (a maize protein). Zein was mixed with functional materials in ratios of 1:1 and 1:2 (w/v) using ethanol as a solvent. After sonication, each mixture was treated up to 550 s at a power of 450 W in a microwave oven. Subsequently, nitrogen was pumped into the solution for 1 h to remove any residual ethanol from the system and the samples were freeze-dried to yield the dry powder. The thermal performance was analyzed using differential scanning calorimetry and thermogravimetric analysis. The encapsulation morphology and chemical structure were analyzed using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Tetradecane was found to be properly encapsulated in the microstructure of zein under two different conditions with an average capsule diameter of 13950 nm. The melting point, crystallization point, and latent heat of encapsulated zein/tet are 4.95, 0.68 °C, and 107 J g⁻¹, respectively. Thermal cycling tests indicated that zein/tet and zein/tet/APC have good thermal stability with negligible changes in their melting and crystallization temperatures. Heat management with tet has been modified using potassium chloride to support a suitable temperature range for food packaging. The encapsulated materials can be potentially used for temperature control during the transport of temperature-sensitive products. Graphical Abstract: [Figure not available: see fulltext.].