The aim of this study was to investigate the stability of L-ascorbic acid(L-AA) and EGCG(Epigallocatechin gallate) in thermal and high pressure process and develop the analysis method for food stability study by NMR.
Most food materials should go through thermal processing for pasteurization, which inevitably induces the degradation of main useful food components such as water-soluble vitamins and tea catechins. HHP (high hydrostatic pressure) is recently introduced as alternative technology of conventional pasteurization processing, because this non-thermal technology keeps the functional materials stable and maintains its fresh flavor and texture. This emerging technology was compared with thermal treatments for evaluation of its availability.
Thermal treatments were conducted in oil-bath (120℃) for 10minutes. Combined pressure and temperature treatment were performed in HHP equipment (Avure autoclave systems, INC) at pressures up to 500MPa combined with temperature (20-50℃).
The quantities of L-AA, EGCG and its degradation products were measured by the quantitative NMR method and HPLC analysis method, respectively.
The nuclear magnetic resonance (NMR) techniques were developed for the simultaneous quantitative analysis of L-AA and EGCG degradation. For the quantitative analysis by using NMR, several NMR experimental conditions were optimized including water-suppression techniques, acquisition (relaxation delay, acquisition time, etc) and processing methods. And sampling method with micro NMR-tube was also developed for food components stability study in normal water. The application of NMR methods in food components stability test has several advantages: rapid and simultaneous multi-components analysis method, non-destructive and accurate method. The degradation products can be analyzed without its standard compounds, which is not possible in HPLC methods.
In the stability study of food components(L-AA, EGCG, Caffeine) under physical processing, L-AA increased the EGCG stability during pasteurized processing. The degradation products of EGCG induced by thermal treatment are considered as oxidant. On the other hand, it is supposed that some kinds of strong antioxidants which are the degradation products of L-AA can be occurred under thermal treatment.