Heat-induced conversion of multiscale molecular structure of natural food nutrients: A review

Thermal process is the most important way of treating foods. Heat energy inputted into the natural food system induces the depolymerization of multi-scale structures of matrix, and causes the intramolecular and intermolecular interactions of different nutrients. It attacks and breaks the original polymeric molecule structures and the functional properties of macronutrients such as carbohydrates, proteins and lipids. Micronutrients such as vitamins and other novel functional ingredients are also thermally converted. The heat-induced conversions of nutrients are slightly or totally with discrepancy in simple-, simulated- and real-food systems, respectively. Thus, this review aims to extensively summarize the heat-induced structural characteristics, thermal conversion pathways and pyrolysis mechanism of nutrients both in simple and complex food matrices. The structural change of each nutrient and its thermal reaction kinetics depend on the molecule structure and polymeric characteristic of the unit substances in the system.