Temperature-responsive microcapsules and their aroma applications and challenges.

Due to the low boiling point, volatilization, sensitivity to heat, and poor solubility in water, it is difficult to ensure that the aroma of products can be stably and lastingly released. Therefore, the microencapsulation of flavor and fragrance can achieve stabilization to some extent. Temperature-responsive microcapsules are a kind of micro-containers that can achieve rapid release of core materials by regulating temperature. They can not only prolong the retention time of aroma, but also realize the smart release of aroma substances by simply changing the temperature. However, since there aren't so many works about the industrialization of temperature-responsive aroma microcapsules, the applications of these microcapsules in products may face certain challenges. In this review, firstly, the classification of wall materials of temperature-responsive aroma microcapsules is summarized and sorted out. Then, the preparation methods of temperature-responsive aroma microcapsules are described, and the release mechanisms of these microcapsules made of colloidal materials are mainly discussed. According to the properties of temperature-responsive materials, the release mechanism of aroma microcapsules is explained from five aspects: phase transition temperature, cloud point, polymer molecular chain conformation transition, glass transition temperature, and Avrami's equation. In the last part of this review, challenges and prospects faced by temperature-responsive aroma microcapsules in research and applications are proposed.