The effect of pressure on the kinetics of polyphenolics degradation – Implications to hyperbaric storage using Epigallocatechin-gallate as a model

Understanding reaction kinetics at elevated pressures is of importance for the development of pressure-based technologies and especially for hyperbaric storage (HS), a potential alternative for the energy-consuming refrigeration. The effect of pressure on degradation kinetics of a polyphenol, Epigallocatechin-gallate (EGCG), was explored at pressures up to 200 MPa (HS levels) for several hours, with and without fructose. In a baroresistant buffer, pressure enhanced EGCG degradation, due to a negative activation volume, while in phosphate buffer the pH decreased (as is also expected to occur in many foods) resulting in a superposition of accelerating and protective effects. A previously undescribed protective, pressure-level dependent, effect of fructose was identified. Novel in situ spectroscopy and HPLC analysis revealed that in addition to the effect on EGCG degradation rate, pressure also modifies the ratios between the numerous degradation products, likely due to a varying effect on the different steps involved in the degradation pathway. Industrial relevance: The effect of pressure on reaction kinetics in food systems can be of great importance in processing conditions combining thermal and high pressure, and critical for the emerging concept of hyperbaric storage, where the food is exposed to high pressures for long duration of time, allowing a plethora of reactions to take place, all varyingly affected by pressure. Yet the effects of pressure on kinetics are often overlooked. Polyphenolic compounds are a large group of molecules responsible for both sensorial and health-promoting functionality in plant-based foods. Those compounds are known to undergo degradation by several mechanisms during processing and storage and their successful conservation is often considered of significant industrial importance. The presented work provides fundamental information regarding the effects of pressure on the kinetics of EGCG (Epigallocatechin-gallate) degradation, as a model for relatively unstable, polyphenolic compound, (taking into account pressure-induced pH shifts, and the presence of co-solutes). EGCG is also of specific importance in many products where it naturally occurs (green tea drinks etc.) and where it is externally added as a valuable supplement.