Optimization of microencapsulation and stability evaluation of astaxanthin-rich shrimp shell extract

The goal of this research was to find the best way to use shrimp shell as a source of astaxanthin and as an agricultural waste in shrimp processing site. For this purpose, first shrimp shell extract was extracted with the assisting ultrasonic . Then it was encapsulated using different walls (modified starch and maltodextrin with hydrolysis degree of 7 and 20) and spray drying method. Wall composition design was performed using response surface method and simplex lattice design with augmented axial points in mixture design (14 wall compositions). Evaluation of physicochemical properties of microcapsules (moisture content, microencapsulating efficiency, astaxanthin content and antioxidant power) showed that the use of a mixture of maltodextrin and modified starch walls up to the center point of the triangular design (33.33%) improved the physicochemical properties compared to using of walls alone. Optimization of different wall concentrations for microencapsulation of shrimp shell extract containing astaxanthin using numerical and graphical optimization showed that the optimal wall composition containing 18.40% of maltodextrin with a hydrolysis degree7, 41.78% of modified starch and 39.81% of maltodextrin with a hydrolysis degree 20. Also, the stability of astaxanthin in microcapsules during 42 days of storage in different conditions of temperature (4 and 25ͦ C) and humidity (52 and 75%) showed that the amount of astaxanthin decreased linear in all samples (linear coefficient more than 98%), but the amount of final astaxanthin in different samples was significantly different from each other (p <0.5). Reducing the temperature and relative humidity of the storage environment resulted in better preservation of astaxanthin in microcapsules and microcapsules containing optimal wall composition and equal composition of each walls at 4 ° C and relative humidity of 52% had the highest stability of astaxanthin with half-life 94.93 and 92.42 days, respectively compared to other microcapsules.