Impacts of Thermal Treatment on the Digestibility of Astaxanthin-enriched Eggs

The objective of this study was to investigate the impacts of four thermal treatments on the stability of astaxanthin-enriched eggs (hot spring, soft-boiled, hard-boiled and pan-fried eggs). And a simulated gastrointestinal tract model was designed to evaluate the lipid and protein digestibility, molecular weight distribution of protein, biostability and bioaccessibility of astaxanthin. Results showed that thermal treatment led to the degradation of astaxanthin. Among these, soft-boiled had the highest retention ratio, 97.21%. Compared with raw eggs, boiled eggs had higher lipid and protein digestibility. Soft-boiled and hot spring eggs exhibited the highest digestibility, however, a lower digestibility was observed on the pan-fried eggs. These results were confirmed by electrophoresis analysis that the fractions with high molecular weight in the soft-boiled and hot spring eggs disappeared. There was no significant difference on the biostability of eggs astaxanthin under different thermal treatment, which was 48.76%~49.47%, while boiling eggs could effectively improve the bioaccessibility as compared with raw eggs. The soft-boiled and hot spring eggs exhibited relatively higher bioaccessibility, 48.76% and 47.71%, respectively. These results suggested that soft-boiled astaxanthin-enriched eggs could be used as a promising approach for natural astaxanthin supplementation.